TION EVALUA ILABLE High-Frequency, Low-Cost SMBus Chargers L

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TION EVALUA ILABLE High-Frequency, Low-Cost SMBus Chargers L

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19-4817; 7/09
TION EVALUA ILABLE
High-Frequency, Low-Cost SMBus Chargers
Low-Cost SMBus Charger High Switching Frequency (1.2MHz, 0.85MHz, 0.5MHz) Internal Boost Switches SMBus-Programmable Charge Voltage, Input Current Limit, Charge Current, Relearn Voltage, Digital IINP Readback Single-Point Compensation Automatic Selection System Power Source Adapter n-channel MOSFETs Driven Internal Dedicated Charge Pump Adapter Soft-Start ±0.4% Accurate Charge Voltage ±2.5% Accurate Input Current Limiting Accurate Charge Current Monitor Outputs Adapter Current (±2% Accuracy) Battery Discharge Current (±2% Accuracy) Adapter Presence Adapter Overvoltage Protection 11-Bit Battery Voltage Setting 6-Bit, Charge-Current Setting/Input Current Setting Improved IINP Accuracy Input Current
General Description
MAX17035/MAX17435/MAX17535 integrated multichemistry battery chargers simplify construction accurate efficient chargers. MAX17035/ MAX17435/MAX17535 provide SMBusK-programmable charge current, charge voltage, input current limit, relearn voltage, digital readback IINP voltage. MAX17035/ MAX17435/MAX17535 utilize charge pump control adapter selection n-channel MOSFETs when adapter present. When adapter absent, charge pump shut down p-channel MOSFET selects battery. MAX17035/MAX17435/MAX17535 provide charge current lithium-ion (Li+) cells series. charge current, input current-limit sense amplifiers have offset errors 10mI sense resistors. MAX17035/MAX17435/MAX17535 fixed-inductor ripple architecture significantly reduces component size circuit cost. MAX17035/MAX17435/MAX17535 provide digital output that indicates presence adapter, analog output that indicates adapter battery current, depending upon presence absence adapter, digital output that indicates when adapter current exceeds user-defined threshold. MAX17035 operates with switching frequency 1.2MHz. MAX17435 switches 850kHz, MAX17535 switches 500kHz. MAX17035/MAX17435/MAX17535 available small, 0.75mm 24-pin, lead-free package. evaluation available.
MAX17035/MAX17435/MAX17535
Ordering Information
PART MAX17035ETG+* MAX17435ETG+ TEMP RANGE -40NC +85NC -40NC +85NC -40NC PIN-PACKAGE TQFN-EP** TQFN-EP**
Applications
Notebook Computers PDAs Mobile Communicators to-4 Cell Battery-Powered Devices
MAX17535ETG+* +85NC TQFN-EP** +Denotes lead(Pb)-free/RoHS-compliant package. *Future product-contact factory availability. **EP Exposed pad.
Configuration
CSSP CSSN
VIEW
IINP
PDSL
ACIN ITHR
CSIP CSIN
BATT ACOK ADAPTLIM
MAX17035 MAX17435 MAX17535
DCIN
SMBus trademark Intel Corp.
Maxim Integrated Products
pricing, delivery, ordering information, please contact Maxim Direct 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
ABSOLUTE MAXIMUM RATINGS
DCIN, CSSP, BATT, CSIP -0.3V +28V CSIP CSIN, CSSP CSSN -0.3V +0.3V VCC, SCL, SDA, VAA, ACIN, ITHR, ADAPTLIM, ACOK -0.3V PDSL GND. -0.3V +37V PGND -0.3V +0.3V .-0.3V (VBST 0.3V) -0.3V -0.3V +34V PGND -0.3V (VLDO 0.3V) +28V IINP GND. -0.3V (VLDO 0.3V) Short Circuit Momentary Continuous Power Dissipation +70NC) 24-Pin, Thin (derate 20.8mW/NC above +70NC) .1666mW Operating Temperature Range -40NC +85NC Junction Temperature .+150NC Storage Temperature Range -65NC +150NC Lead Temperature (soldering, 10s).+300NC
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, +85°C, unless otherwise noted. Typical values +25°C.) PARAMETER INPUT SUPPLIES Adapter Present Quiescent Current (Note IDCIN ICSSP ICSSN IVCC Charging enabled, VADAPTER 19V, VBATTERY 16.8V Charging disabled BATT CSIP CSIN Input Current DCIN Input Current Supply Current DCIN Input-Voltage Range Charger DCIN Undervoltage-Lockout Trip Point Charger DCIN Input-Voltage Range CHARGE-VOLTAGE REGULATION ChargingVoltage() 0x41A0 ChargingVoltage() 0x3130 ChargingVoltage() 0x20D0 ChargingVoltage() 0x1060 Battery Undervoltage-Lockout Trip Point Trickle Charge 16.733 -0.4 12.516 -0.6 8.333 -0.8 4.15 -1.0 4.192 12.592 16.8 16.867 +0.4 12.668 +0.6 8.467 +0.8 4.234 +1.0 VDCIN falling VDCIN rising IDCIN VBATT 16.8V Adapter absent charger shut down (Note SYMBOL CONDITIONS UNITS
VBATT 19V, adapter present (Note Charger disabled Charger added
Battery Full-Charge Voltage Accuracy
High-Frequency, Low-Cost SMBus Chargers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, +85°C, unless otherwise noted. Typical values +25°C.) PARAMETER CSIP-to-CSIN Full-Scale Current-Sense Voltage 10mI, Figure ChargingCurrent()= 0x1f80 Charge Current Accuracy 10mI, Figure ChargingCurrent()= 0x0f80 10mI, Figure ChargingCurrent()= 0x0080 Charge-Current Gain Error INPUT CURRENT REGULATION 10mW, Figure InputCurrent() full scale Input Current-Limit Threshold 10mW, Figure InputCurrent() 0C80 10mW, Figure InputCurrent() 0780 CSSP/CSSN Input-Voltage Range IINP Voltage Gain IINP Output-Voltage Range VCSSP VCSSN 110mV IINP Accuracy VCSSP VCSSN 55mV VCSSP VCSSN IINP Gain Error IINP Offset Error REFERENCE Output Voltage Undervoltage-Lockout Threshold LINEAR REGULATOR Output Voltage Load Regulation Undervoltage-Lockout Threshold IREF 50FA ILDO 40mA falling 5.25 IREF 50FA falling 4.082 4.096 4.115 Based VCSSP VCSSN 110mV VCSSP VCSSN 55mV Based VCSSP VCSSN 110mV VCSSP VCSSN 55mV 106.7 -2.5 62.08 36.86 19.7 -1.5 -350 19.85 38.4 113.3 +2.5 65.92 39.94 20.3 +1.5 +350 Based ChargeCurrent() 128mA 8.064A SYMBOL CONDITIONS UNITS CHARGE-CURRENT REGULATION 78.22 7.822 3.829 -3.5 3.968 80.64 8.064 83.06 8.306 4.107 +3.5
MAX17035/MAX17435/MAX17535
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, +85°C, unless otherwise noted. Typical values +25°C.) PARAMETER ACOK ACOK Sink Current ACOK Leakage Current ACIN ACIN Threshold ACIN Threshold Hysteresis ACIN Falling Delay ACIN Input-Bias Current ITHR/ADAPTLIM ITHR Leakage Current ADAPTLIM Sink Current ADAPTLIM Leakage Current ITHR Threshold LOGIC LEVELS SDA/SCL Input Voltage SDA/SCL Input High Voltage SDA/SCL Input-Bias Current SWITCHING REGULATOR VDCIN 19V, VBATT 10V, MAX17035 Off-Time Factor Sense Voltage Minimum Discontinuous Mode Ripple Current Zero-Crossing Comparator Threshold Cycle-by-Cycle Current-Limit Sense Voltage Resistance High Resistance Resistance High Resistance ADAPTER DETECTION Adapter Absence Detect Threshold Adapter Detect Threshold CHARGE-PUMP MOSFET DRIVER PDSL Gate-Driver Source Current PDSL Gate-Driver Output Voltage High VPDSL VDCIN VDCIN VDCIN 19V, open load VDCIN VDCIN VDCIN VBATT, VDCIN falling VDCIN VBATT, VDCIN rising VDCIN 19V, VBATT 10V, MAX17435 VDCIN 19V, VBATT 10V, MAX17535 VCSIP VCSIN ns/V +25NC VITHR LDO, +25NC VITHR VIINP VITHR VIINP, +25NC Calculated VITHR VIINP +25NC SYMBOL CONDITIONS VACOK 0.4V, ACIN 2.5V VACOK 5.5V, ACIN 0.5V, +25NC 1.465 1.485 1.53 UNITS
VCSIP VCSIN VCSIP VCSIN IDHI 10mA IDHI -10mA IDLO 10mA IDLO -10mA
High-Frequency, Low-Cost SMBus Chargers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, +85°C, unless otherwise noted. Typical values +25°C.) PARAMETER ACOVP Threshold ACOVP Threshold Hysteresis ADAPTER OVERCURRENT PROTECTION ACOCP Threshold ACOCP Blanking Time ACOCP Waiting Time PDSL SWITCH CONTROL PDSL Turn-Off Resistance SMBus TIMING SPECIFICATIONS SMBus Frequency Free Time START Condition Hold Time from START Condition Setup Time from STOP Condition Setup Time from Holdup Time from Setup Time from Period High Period Maximum Charging Period Without Charge_Voltage() ChargeCurrent() Command fSMB tBUF tHD:STA tSU:STA tSU:STO tHD:DAT tSU:DAT tLOW tHIGH When ACOCP comparator high time blanking time expires With respect VCSSP VCSSN SYMBOL Rising CONDITIONS 2.04 UNITS ADAPTER OVERVOLTAGE PROTECTION
MAX17035/MAX17435/MAX17535
ELECTRICAL CHARACTERISTICS
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, -40°C +85°C, unless otherwise noted.) (Note PARAMETER INPUT SUPPLIES Adapter Present Quiescent Current IDCIN ICSSP ICSSN (Note Charging enabled, VADAPTER 19V, VBATTERY 16.8V Charging disabled SYMBOL CONDITIONS UNITS
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, -40°C +85°C, unless otherwise noted.) (Note PARAMETER BATT CSIP CSIN Input Current DCIN Input Current DCIN Standby Supply Current Supply Current DCIN Input-Voltage Range Charger DCIN Undervoltage-Lockout Trip Point Charger DCIN Input-Voltage Range CHARGE-VOLTAGE REGULATION ChargingVoltage() 0x41A0 ChargingVoltage() 0x3130 ChargingVoltage() 0x20D0 ChargingVoltage() 0x1060 Battery Undervoltage-Lockout Trip Point Trickle Charge CHARGE-CURRENT REGULATION CSIP-to-CSIN Full-Scale Current-Sense Voltage 10mI, Figure ChargingCurrent() 0x1f80 Charge Current Accuracy 10mI, Figure ChargingCurrent()= 0x0f80 10mI, Figure ChargingCurrent() 0x0080 Charge-Current Gain Error Based ChargeCurrent() 128mA 8.064A 78.22 7.822 3.829 -3.5 83.06 8.306 4.107 +3.5 16.73 -0.416 12.516 -0.6 8.333 -0.8 4.15 -1.0 16.87 +0.416 12.668 +0.6 8.467 +0.8 4.234 +1.0 VDCIN falling VDCIN rising IDCIN SYMBOL VBATT 16.8V CONDITIONS Adapter absent charger shut down (Note UNITS
VBATT 19V, adapter present (Note Charger disabled DCIN Charger enabled
Battery Full-Charge Voltage Accuracy
High-Frequency, Low-Cost SMBus Chargers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, -40°C +85°C, unless otherwise noted.) (Note PARAMETER INPUT CURRENT REGULATION 10mI, Figure InputCurrent() full scale Input Current-Limit Threshold 10mI, Figure InputCurrent()= 0C80 10mI, Figure InputCurrent()= 0780 CSSP/CSSN Input Voltage Range IINP Voltage Gain IINP Output-Voltage Range VCSSP VCSSN 110mV IINP Accuracy VCSSP VCSSN 55mV VCSSP VCSSN IINP Gain Error IINP Offset Error REFERENCE Output Voltage UndervoltageLockout Threshold LINEAR REGULATOR Output Voltage Load Regulation Undervoltage-Lockout Threshold ACOK ACOK Sink Current ACIN ACIN Threshold ACIN Threshold Hysteresis ACIN Input-Bias Current ITHR/ADAPTLIM ITHR Leakage Current ADAPTLIM Sink Current ADAPTLIM Leakage Current ITHR Threshold VITHR 5.4V VITHR VIINP VITHR VIINP Calculated VITHR VIINP IREF 50FA ILDO 40mA falling 5.25 IREF 50FA falling 4.075 4.115 Based VCSSP VCSSN 100mV VCSSP VCSSN 20mV Based VCSSP VCSSN 100mV VCSSP VCSSN 106.7 -2.5 62.08 36.86 19.7 -500 113.3 +2.5 65.92 39.94 20.3 +500 SYMBOL CONDITIONS UNITS
MAX17035/MAX17435/MAX17535
VACOK 0.4V, ACIN 2.5V
1.465 1.53
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, -40°C +85°C, unless otherwise noted.) (Note PARAMETER LOGIC LEVELS SDA/SCL Input Voltage SDA/SCL Input High Voltage SDA/SCL Input-Bias Current SWITCHING REGULATOR VDCIN 19V, VBATT 10V, MAX17035 Off-Time Factor Cycle-by-Cycle Current-Limit Sense Voltage Resistance High Resistance Resistance High Resistance ADAPTER DETECTION Adapter Absence Detect Threshold Adapter Detect Threshold CHARGE-PUMP MOSFET DRIVER PDSL Gate-Driver Output-Voltage High ADAPTER OVERVOLTAGE PROTECTION ACOVP Threshold PDSL SWITCH CONTROL PDSL Turn-Off Resistance SMBus TIMING SPECIFICATIONS SMBus Frequency Free Time START Condition Hold Time from START Condition Setup Time from STOP Condition Setup Time from fSMB tBUF tHD:STA tSU:STA tSU:STO Rising 2.04 VDCIN VBATT, VDCIN falling VDCIN VBATT, VDCIN rising VDCIN VDCIN VDCIN 19V, VBATT 10V, MAX17435 VDCIN 19V, VBATT 10V, 17535 VCSIP VCSIN IDHI 10mA IDHI -10mA IDLO 10mA IDLO -10mA ns/V SYMBOL CONDITIONS UNITS
High-Frequency, Low-Cost SMBus Chargers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit Figure load LDO, VDCIN VCSSP VCSSN 19V, VBST VBATT VCSIP VCSIN 16.8V, -40°C +85°C, unless otherwise noted.) (Note PARAMETER Hold Time from Setup Time from Period High Period Maximum Charging Period Without Charge_Voltage() ChargeCurrent() Command SYMBOL tHD:DAT tSU:DAT tLOW tHIGH CONDITIONS UNITS
MAX17035/MAX17435/MAX17535
Note Adapter Present conditions tested VDCIN VBATT 16.8V. Adapter Absent conditions tested VDCIN 16V, VBATT 16.8V. Note Specifications -40°C guaranteed design production tested.
Typical Operating Characteristics
(Circuit Figure 19V, VCC, +25NC, unless otherwise specified.)
INPUT CURRENT-LIMIT ERROR INPUT CURRENT-LIMIT SETTING
INPUT CURRENT-LIMIT SETTING
MAX17035 toc01
INPUT CURRENT-LIMIT ERROR SYSTEM CURRENT
-0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -3.5 -4.0 SYSTEM CURRENT
MAX17035 toc02
IINP ERROR SYSTEM CURRENT SWEEP)
IINP ERROR
MAX17035 toc03
INPUT CURRENT-LIMIT ERROR
INPUT CURRENT-LIMIT ERROR
VBATT 8.4V
VBATT 12.6V VBATT 16.8V INPUT CURRENT LIMIT 3.584A
VADAPTER VADAPTER VBATT
VCSSP VCSSN (mV)
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
Typical Operating Characteristics (continued)
(Circuit Figure 19V, VCC, +25NC, unless otherwise specified.)
CHARGER-CURRENT ERROR BATTERY VOLTAGE
MAX17035 toc05
MAX17035 toc04
IINP ERROR SYSTEM CURRENT
-5.0
CHARGER-CURRENT ERROR SMBS SETTING
CHARGER-CURRENT ERROR
MAX17035 toc06
CHARGER-CURRENT ERROR
INPUT CURRENT LIMIT 3.584A
IINP ERROR
ICHARGER
ICHARGER ICHARGER
VBATT 16.8V VBATT 12.6V
SYSTEM CURRENT
VBATT 8.4V
-0.5 BATTERY VOLTAGE
INPUT CURRENT-LIMIT SETTING
CHARGE VOLTAGE ACCURACY 3.854A
MAX17035 toc07
CHARGER VOLTAGE ERROR CHARGER CURRENT
CHARGER VOLTAGE ERROR -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7
MAX17035 toc08
BATTERY REMOVAL (VBATT
0.20 0.15 0.10 0.05 -0.05 -0.10 -0.15 CHARGE VOLTAGE
MAX17035 toc09
ERROR
VBATT 16.8V
VBATT 8.4V
VBATT 12.6V
PDSL 5V/div VBATT 5V/div DCIN 5V/div
1A/div
100Fs/div
CHARGER CURRENT
SYSTEM LOAD TRANSIENT
MAX17035 toc10
CHARGE-OUTPUT SHORT CIRCUIT
1A/div
MAX17035 toc11
EFFICIENCY CHARGE CURRENT CELLS)
EFFICIENCY VBATT 5V/div CHARGE CURRENT
CELL CELL
VBATT 200mV/div 1V/div ISYSLD 1A/div
CELL
2A/div
1ms/div
20Fs/div
MAX17035 toc12
High-Frequency, Low-Cost SMBus Chargers
Typical Operating Characteristics (continued)
(Circuit Figure 19V, VCC, +25NC, unless otherwise specified.)
MAX17035/MAX17435/MAX17535
VOLTAGE CURRENT
MAX17035 toc13
DEVIATION, SWITCHING SWITCHING
DEVIATION (mV) -0.5 -1.0 -1.5 -2.0
4.080
MAX17035 toc14
TEMPERATURE
MAX17035 toc15
5.48 5.46 VOLTAGE 5.44 5.42 5.40 5.38 5.36 5.34
4.110 4.105 VOLTAGE 4.100 4.095 4.090 4.085
SWITCHING
SWITCHING
DCIN
CURRENT (mA)
TEMPERATURE (NC)
FREQUENCY VBATT ICHG
FREQUENCY (kHz) VBATT
MAX17035 toc16
POWER-SOURCE SELECTOR SCHEME WITH BATTERY PRESENT (ADAPTER REMOVAL)
POWER-SOURCE SELECTOR SCHEME WITH BATTERY PRESENT (ADAPTER INSERTION)
1000
MAX17035 toc17
MAX17035 toc18
VADAPTER 5V/div VSYSLD 5V/div VBATT 5V/div
PDSL 5V/div
PDSL 5V/div VSYSLD 5V/div VBATT 5V/div
VADAPTER 5V/div 10ms/div 40ms/div
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
Description
NAME FUNCTION SMBus Clock Input. Connect external pullup resistor according SMBus specifications. SMBus Data I/O. Open-drain output. Connect external pullup resistor according SMBus specifications. Charger Supply Input. Connect adapter supply. minimum input bias current connect center input/soft-start FETs. Bypass with ceramic capacitor PGND placed close pin. resistor reduce input surge adapter insertion. Linear Regulator Output. This 30mA reference also powers driver, circuit, internal SMBus circuitry. Bypass with ceramic capacitor PGND placed close pin. This output disabled when charger disabled. Low-Side Power-MOSFET Driver Output. Connect low-side n-channel MOSFET gate. Adaptive System Current-Limit Comparator Output. This open-drain output high impedance when voltage IINP lower than ITHR threshold. typical application, 10kW pullup resistor (pin High-Side Driver Supply. Connect 0.1FF capacitor from High-Side Driver Source Connection High-Side Power MOSFET Driver Output. Connect high-side n-channel MOSFET gate. Detect Output .This open-drain output high impedance when ACIN lower than 1.5V. ACOK output remains high when MAX17035/MAX17435/MAX17535 powered down. typical application, 10kI pullup resistor (pin Output Current-Sense Negative Input. Connect this negative terminal sense resistor. Setting Charge Current section resistor value scaling. Output Current-Sense Positive Input. Connect current-sense resistor from CSIP CSIN; voltage across these pins interpreted MAX17035/MAX17435/MAX17535 proportional charge current delivered battery with approximately 110mV full-scale voltage. Setting Charge Current section resistor value scaling. Battery Voltage Feedback Input. Connect close possible battery terminal. Power-Source n-Channel MOSFET Switch Driver Output. When adapter present overvoltage event detected input, PDSL output pulled with 2.5kW (typ) resistor. Otherwise, typically above adapter voltage when part using battery. This powered internal charge pump. Input Current-Sense Negative Input. description CSSP resistor value scaling. Current Sense Positive Input. Connect current-sense resistor from CSSP CSSN. voltage across CSSP CSSN determines current which charger reduces charging current keep from drawing more current from adapter than allowed. system current flowing resistor from CSSN CSSP increases, charger reduces charge current keep system current limit value. When system current reaches approximately 130% programmed value, PDSL changes state turns input prevent excess current from adapter. When adapter overcurrent condition occurs, give 16ms blanking time, then turn adapter switch. adapter switch turned again after 0.6s. same thing more time. After third blanking time (16ms), adapter MOSFETS latched state. release adapter switch's state, adapter removal reinsertion needed.
DCIN
ADAPTLIM ACOK
CSIN
CSIP
BATT
PDSL
CSSN
CSSP
High-Frequency, Low-Cost SMBus Chargers
Description (continued)
NAME IINP FUNCTION Voltage Regulation Loop-Compensation Point. Connect 10nF capacitor from GND. Input Current-Monitor Output. voltage IINP times voltage from CSSP CSSN. This voltage present when charging enabled monitor system current, when battery discharging monitor battery discharge current. Adapter-Detect Input. ACIN input comparator with comparison voltage about 1.5V. output comparator ACOK. ACOK goes when threshold voltage exceeded indicate that adapter present, enables charger. When ACIN input above 2.1V, MAX17035/MAX17435/MAX17535 interpret that adapter overvoltage event. charger then disabled adapter MOSFETs turned off. part charging ACIN voltage drops below programmed threshold, charger disabled ChargeCurrent() ChargeVoltage() command have written over SMBus reenable charger. Adaptive System Current-Limit Comparator Threshold. This connects inverting input comparator. noninverting input comparator IINP input, while output driving ADAPTLIM open drain. When input ITHR greater than IINP, ADAPTLIM output high. 4.096V Internal Reference Voltage; External Load Allowed. Bypass analog ground using greater ceramic capacitor. Circuitry Supply-Voltage Input. Connect through bypass with 0.1FF capacitor close possible package pin. Analog Ground Enable/Disable Charger Operation. This disables charger associated circuitry when goes addition ACOK charger enable. adapter absent pulled voltage higher than 2.4V, battery-discharge current monitor IINP enabled. Exposed Pad. Connect backside exposed power ground.
MAX17035/MAX17435/MAX17535
ACIN
ITHR
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
10mI
ADAPTER
103kI
10nF
SYSTEM LOAD
150kI
DCIN
PDSL
CSSP
CSSN
10kI
ACIN
0.1FF
4.7FF 4.7FF
ACOK 10kI
ACOK PGND
MAX17035
CSIP CSIN
10mI
BATT 0.01FF 0.1FF COUT BATTERY IINP VOLTAGE 10kI ADAPTLIM 10kI ITHR 7.06kI 49.9kI ADAPTER CURRENT LIMIT FLAG
IINP
10kI SMBus CONTROL
10kI
Figure Standard Application Circuit
Detailed Description
MAX17035/MAX17435/MAX17535 charger includes functions necessary charge Li+, NiMH, NiCd smart batteries. high-efficiency synchronous rectified step-down DC-DC converter used implement constant-current constant-voltage charger. DC-DC converter drives high-side n-channel MOSFET provides synchronous rectification with
low-side n-channel MOSFET. charge current input current-sense amplifiers have low-input offset errors (200FV typ), allowing small-valued sense resistors. MAX17035/MAX17435/MAX17535 SMBus interface similar MAX8731A charge current, charge voltage, input current limit. addition, MAX17035/MAX17435/MAX17535 SMBus interface supports RELEARN(), IINPVoltage() readback.
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
IINP PGND PGND
DCIN 5.4V REGULATOR CSIN CSSP 20V/V CSSN IN_SET DCIN 4.096V REFERENCE CURRENTSENSE AMPLIFIER CHARGE VOLTAGE() +200mV BATTERY ACOVP
ADAPTER PRESENT HIGH-SIDE DRIVER LOW-SIDE DRIVER
DC-DC CONVERTER
MAX17035
AC_EN
ZCMP
CSIP
CURRENTSENSE AMPLIFIER
IMAX
CCMP
IMIN
CSIN BDIV
128mA
BATT
SWITCH LOGIC
ADAPTLIM
CHG_EN IINP SMBus LOGIC CHARGE VOLTAGE() RELEARN() CHARGE CURRENT() INPUT CURRENT()
11-BIT VCTL 6-BIT ISET 7-BIT IN_SET 6-BIT READBACK
AC_EN PDSL LOGIC
1.5V
ACIN
ACOK
ITHR
PDSL
Figure Block Diagram
MAX17035/MAX17435/MAX17535 control input current (CCS control loop), charge current (CCI control loop), charge voltage (CCV control loop), depending operating condition. three control loops, CCV, CCI, CCS, brought together internally lowest voltage clamp (LVC) amplifier. output amplifier feedback control signal DC-DC controller. minimum voltage CCV, CCI, appears output amplifier
clamps other control loops within 0.3V above control point. Clamping other control loops close lowest control loop ensures fast transition with minimal overshoot when switching between different control loops (see Compensation section). loop internally compensated loops share common compensation network dominant control loop (CCV, CCS) drives compensation network.
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
Table Function
ADAPTER PRESENT High High PDSL STATUS PDSL pumped above DCIN voltage (charge pump on). PDSL pumped above DCIN voltage (charge pump on). Charge pump PDSL forced (typ, 27C). Charge pump PDSL forced (typ, 27C). CHARGER STATUS Enabled Disabled Disabled Disabled SYSTEM CURRENT MONITOR STATUS (IINP PATH) Enabled Enabled Enabled Disabled
logic input. state presence absence adapter determines state PDSL, IINP path, charger function shown Table 5.4V powered from DCIN compensated loads from 30mA with single ceramic capacitor. load regulation over 30mA load 34mV (typ), 100mV max. supplies drive driver also circuitry. shut down when adapter absent. IINP monitors system-input current sensed across sense resistor (RS1) that connects between CSSP CSSN. voltage IINP proportional input current according following equation: IINPUT VIINP
Table Fault Protection Shutdown Operation Table
MODE Thermal Fault (Latched, Reset with Adapter Insertion) CONTROLLER STATE Charger disabled DRIVER STATE
30mA
Analog Input Current Monitor Output
where IINPUT current supplied adapter gain (20V/V typ). IINP 2.2V output-voltage range. Table shows charge IINP status when adapter present absent function pin. When connected shown standard application circuit, IINP monitors input system current when adapter present battery discharge current when adapter absent. Leave IINP unconnected used. Table fault-protection shutdown operation table. inputs from SMBus interface. MAX17035/MAX17435/
MAX17535 subset commands documented System Management Specifications V2.0, which downloaded from www.smbus.org. MAX17035/MAX17435/MAX17535 SMBus readword write-word protocols communicate with system controller. MAX17035/MAX17435/MAX17535 operate only slave devices with address 0b0001001_ (0x12) initiate communication bus. addition, MAX17035/MAX17435/MAX17535 have identification registers: (0xFE), 16-bit device register 16-bit manufacturer register (0xFF). SMBus implementation similar MAX8731A with addition RELEARN() IINPVoltage() commands. SMBus powered from external supply, during states that disable charger, SMBus register data lost, register data must rewritten when reenabled. Figure data (SDA) clock (SCL) pins have Schmitttrigger inputs that accommodate slow edges. Choose pullup resistors achieve rise times according SMBus specifications. Communication starts when master signals START condition, which high-to-low transition SDA, while high. When master finished communicating, master issues STOP condition, which low-to-high transition SDA, while high. then free another transmission.
SMBus Implementation
High-Frequency, Low-Cost SMBus Chargers
Figures show timing diagrams signals SMBus interface. address byte, command byte, data bytes transmitted between START STOP conditions. state allowed change only while low, except START STOP conditions. Data transmitted 8-bit bytes sampled rising edge SCL. Nine clock cycles required transfer each byte MAX17035/ MAX17435/MAX17535 because either master slave acknowledges receipt correct byte during ninth clock. MAX17035/MAX17435/MAX17535 support charger commands described Table
MAX17035/MAX17435/MAX17535
Write-Word Format SLAVE ADDRESS bits PRESET 0b0001001 COMMAND BYTE bits Relearn 0x3D ChargingCurrent() 0x14 ChargerVoltage() 0x15 DATA BYTE bits HIGH DATA BYTE bits
Read-Word Format SLAVE ADDRESS bits PRESET 0b0001001 COMMAND BYTE bits INP_Voltage 0x3E SLAVE ADDRESS bits PRESET 0b0001001 DATA BYTE bits HIGH DATA BYTE bits NACK
LEGEND: START CONDITION REPEATED START CONDITION ACKNOWLEDGE (LOGIC-LOW) WRITE (LOGIC-LOW) MASTER SLAVE SLAVE MASTER
STOP CONDITION NACK ACKNOWLEDGE (LOGIC-HIGH) READ (LOGIC-HIGH)
Figure SMBus Write-Word Read-Word Protocols
tLOW
tHIGH
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT
tHD:DAT
tSU:STO tBUF ACKNOWLEDGE CLOCKED INTO MASTER ACKNOWLEDGE CLOCK PULSE STOP CONDITION, DATA EXECUTED SLAVE START CONDITION
START CONDITION ADDRESS CLOCKED INTO SLAVE ADDRESS CLOCKED INTO SLAVE CLOCKED INTO SLAVE SLAVE PULLS SMBDATA LINE
ACKNOWLEDGE CLOCKED INTO MASTER DATA CLOCKED INTO SLAVE DATA CLOCKED INTO SLAVE SLAVE PULLS SMBDATA LINE
Figure SMBUs Write Timing
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
tLOW tHIGH
SMBCLK
SMBDATA
tSU:STA tHD:STA START CONDITION ADDRESS CLOCKED INTO SLAVE ADDRESS CLOCKED INTO SLAVE CLOCKED INTO SLAVE
tSU:DAT
tHD:DAT SLAVE PULLS SMBDATA LINE ACKNOWLEDGE CLOCKED INTO MASTER DATA CLOCKED INTO MASTER DATA CLOCKED INTO MASTER
tSU:DAT
tSU:STO
tBUF
ACKNOWLEDGE CLOCK PULSE STOP CONDITION START CONDITION
Figure SMBus Read Timing
MAX17035/MAX17435/MAX17535 support four battery-charger commands that either write-word read-word protocols summarized Table ManufacturerID() DeviceID() used identify MAX17035/MAX17435/MAX17535. MAX17035/ MAX17435/MAX17535 ManufacturerID() always returns 0x004D DeviceID() always returns 0x0008. output voltage, SMBus write 16-bit ChargeVoltage() command using data format listed Table ChargeVoltage() command uses write-word protocol (see Figure command code ChargeVoltage() 0x15 (0b00010101). MAX17035/MAX17435/MAX17535 provide chargevoltage range 4.095V 19.200V, with 16mV resolution. ChargeVoltage() below 4.095V terminate charging. Upon reset, ChargeVoltage() ChargeCurrent() values cleared charger remains until both ChargeVoltage() ChargeCurrent() command sent. Both remain until charger restarted.
Battery Charger Commands
Setting Charge Voltage
charge current, SMBus write 16-bit ChargeCurrent() command using data format listed Table ChargeCurrent() command uses write-word protocol (see Figure command code ChargeCurrent() 0x14 (0b00010100). When 10mI, MAX17035/MAX17435/MAX17535 provide chargecurrent range 128mA 11.004A, with 128mA resolution. sense resistor other than 10mI used, current limit must scaled RS/10mI, where sense resistor value used circuit. ChargeCurrent() terminate charging. Upon reset, ChargeVoltage() ChargeCurrent() values cleared charger remains until both ChargeVoltage() ChargeCurrent() command sent. Both remain until charger restarted. MAX17035/MAX17435/MAX17535 include fault limiter low-battery conditions. battery voltage less than charge current temporarily 128mA. ChargeCurrent() register preserved becomes active again when battery voltage higher than This function effectively provides foldback current limit that protects charger during short circuit overload.
Setting Charge Current
Table Battery Charger Command Summary
COMMAND 0x14 0x15 0x3D 0x3E 0x3F 0xFE 0xFF COMMAND NAME ChargeCurrent() ChargeVoltage() Relearn Voltage IINPVoltage() InputCurrent() ManufacturerID() DeviceID() READ/WRITE Write only Write only Read write Read only Write only Read only Read only DESCRIPTION 6-bit charge-current setting 11-bit charge-voltage setting 11-bit relearn voltage enable/status Digital read IINP voltage 6-bit charge-current setting Manufacturer Device STATE 0x0000 0x0000 0x4B00 0x0080 0x004D 0x0008
High-Frequency, Low-Cost SMBus Chargers
Table ChargeVoltage() (0x15)
NAME Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV Charge Voltage, DACV DESCRIPTION used. Normally weight. used. Normally weight. used. Normally weight. used. Normally weight. Adds charger voltage compliance, 4095mV min. Adds 16mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 32mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 64mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 128mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 256mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 512mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 1024mV charger voltage compliance. Adds charger voltage compliance, 4095mV min. Adds 2048mV charger voltage compliance. Adds charger voltage compliance. Adds 4096mV charger voltage compliance. Adds charger voltage compliance. Adds 8192mV charger voltage compliance. Adds charger voltage compliance. Adds 16384mV charger voltage compliance, 19200mV max. used. Normally 32768mV weight.
MAX17035/MAX17435/MAX17535
Table ChargeCurrent() (0x14) (10mI Sense Resistor, RS2)
NAME Charge Current, DACI Charge Current, DACI DESCRIPTION used. Normally weight. used. Normally weight. used. Normally weight. used. Normally weight. used. Normally 16mA weight. used. Normally 32mA weight. used. Normally 64mA weight. Adds charger current compliance. Adds 128mA charger current compliance. Adds charger current compliance. Adds 256mA charger current compliance.
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
Table ChargeCurrent() (0x14) (10mI Sense Resistor, RS2) (continued)
NAME Charge Current, DACI Charge Current, DACI Charge Current, DACI Charge Current, DACI DESCRIPTION Adds charger current compliance. Adds 512mA charger current compliance. Adds charger current compliance. Adds 1024mA charger current compliance. Adds charger current compliance. Adds 2048mA charger current compliance. Adds charger current compliance. Adds 4096mA charger current compliance, 8064mA used. Normally 8192mA weight. used. Normally 16386mA weight. used. Normally 32772mA weight.
System current normally fluctuates portions system powered sleep. using inputcurrent-limit circuit, output-current requirement wall adapter lowered, reducing system cost.
Setting Input-Current Limit
total input current estimated follows:
IINPUT SYSTEM CHARGER CHARGE VBATTERY (VIN
where efficiency DC-DC converter (typically 95%). input current limit, issue SMBus command InputCurrent() using 16-bit data format listed Table InputCurrent() command uses writeword protocol (see Figure command code InputCurrent() 0x3F (0b00111111). When 10mI, MAX17035/MAX17435/MAX17535 provide input current-limit range 256mA 11.004A with 256mA resolution. resistor other than 10mI used, input current limit scaled factor 10mI/RS1. InputCurrent() settings from 128mA result current limit 128mA. Upon reset, input current limit 128mA. relearn voltage issue, SMBus command RelearnVoltage() uses 16-bit data format listed Table RelearnVoltage() command uses write-word read-word protocols (see Figure command code RelearnVoltage() 0x3D (0b00111101). MAX17035/MAX17435/MAX17535 provide charge-voltage range 4.095V 19.200V with 16mV resolution. When relearn function enabled setting PDSL switches input-voltage switches battery FET, enabling discharging battery. battery voltage monitored until battery voltage reaches relearn voltage thus known state charge. PDSL state then reset allow charging zero.
total input current system supply current, charge current flowing into battery, current required charger. When input current exceeds input current limit with InputCurrent() command, MAX17035/MAX17435/ MAX17535 reduce charge current provide priority system load current. system supply current increases, charge current reduced needed maintain total input current input current limit. MAX17035/MAX17435/MAX17535 decrease charge current zero, necessary, reduce input current input current limit. Thereafter, system current continues increase, there nothing MAX17035/MAX17435/MAX17535 maintain input current input current limit. system current continues increase total input current increase until ACOCP threshold (which maximum setting) reached MAX17035/MAX17435/ MAX17535 drive PDSL remove input voltage. MAX17035/MAX17435/MAX17535 wait 0.6s then charge again; after 16ms blanking period current again over ACOCP threshold, again opens input voltage. goes through this cycle three times; after three times, MAX17035/MAX17435/ MAX17535 wait adapter voltage removed reinserted before reconnects input voltage.
Setting Relearn Voltage
High-Frequency, Low-Cost SMBus Chargers
Table InputCurrent() (0x3F) (10mI Sense Resistor, RS1)
NAME Input Current, DACS Input Current, DACS Input Current, DACS Input Current, DACS Input Current, DACS Input Current, DACS DESCRIPTION used. Normally weight. used. Normally weight. used. Normally weight. used. Normally 16mA weight. used. Normally 32mA weight. used. Normally 64mA weight. used. Normally 128mA weight. Adds input current compliance. Adds 256mA input current compliance. Adds input current compliance. Adds 512mA input current compliance. Adds input current compliance. Adds 1024mA input current compliance. Adds input current compliance. Adds 2048mA input current compliance. Adds input current compliance. Adds 4096mA input current compliance. Adds input current compliance. Adds 8192mA input current compliance, 11004mA max. used. Normally 16384mA weight. used. Normally 32768mA weight. used. Normally 65536mA weight.
MAX17035/MAX17435/MAX17535
Table Relearn() (0x3D)
NAME DESCRIPTION Disables relearn function. Enables relearn function. When relearn threshold crossed battery discharges, reset zero MAX17035/MAX17435/MAX17535. used. used. used. Adds relearn threshold compliance, 1024 min. Adds 16mV relearn threshold compliance. Adds relearn threshold compliance, 1024 min. Adds 32mV relearn threshold compliance. Adds relearn threshold compliance, 1024 min. Adds 64mV relearn threshold compliance. Adds relearn threshold compliance, 1024 min. Adds 128mV relearn threshold compliance. Adds relearn threshold compliance, 1024 min. Adds 256mV relearn threshold compliance.
Relearn,
Relearn, Relearn, Relearn, Relearn, Relearn,
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
read digital version IINP voltage, issue SMBus command IINPVoltage() command using data format listed Table command code IINPVoltage() 0x3E (0b00111110). IINPVoltage() command uses read-word protocol (see Figure
Reading IINP Voltage
MAX17035/MAX17435/MAX17535 include timer terminate charging charger received ChargeVoltage() ChargeCurrent() command within 175s. timeout occurs, both ChargeVoltage() ChargeCurrent() commands must sent again reenable charging.
Charger Timeout
Table Relearn() (0x3D) (continued)
NAME Relearn, Relearn, Relearn, Relearn, Relearn, Relearn, DESCRIPTION Adds relearn threshold compliance, 1024 min. Adds 512mV relearn threshold compliance. Adds relearn threshold compliance. Adds 1024mV relearn threshold compliance. Adds relearn threshold compliance. Adds 2048mV relearn threshold compliance. Adds relearn threshold compliance. Adds 4096mV relearn threshold compliance. Adds relearn threshold compliance. Adds 8192mV relearn threshold compliance. Adds relearn threshold compliance. Adds 16384mV relearn threshold compliance, 19200mV max. used.
Table IINPVoltage() (0x3E)
NAME IINP Voltage, DACV IINP Voltage, DACV IINP Voltage, DACV IINP Voltage, DACV IINP Voltage, DACV IINP Voltage, DACV DESCRIPTION used. Normally weight. used. Normally weight. used. Normally weight. used. Normally weight. used. Normally 16mV weight. Adds IINP voltage. Adds 12.8mV IINP voltage. Adds IINP voltage. Adds 25.6mV IINP voltage. Adds IINP voltage. Adds 51.2mV IINP voltage. Adds IINP voltage. Adds 102.4mV IINP voltage. Adds IINP voltage. Adds 204.8mV IINP voltage. Adds IINP voltage. Adds 409.6mV IINP voltage.
High-Frequency, Low-Cost SMBus Chargers
Table IINPVoltage() (0x3E) (continued)
NAME IINP Voltage, DACV IINP Voltage, DACV DESCRIPTION Adds IINP voltage. Adds 819.2V IINP voltage maximum 2.20V. Adds IINP voltage. Adds 1.6384V IINP voltage maximum 2.20V. used. Normally 8192mV weight. used. Normally 16384mV weight. used. Normally 32768mV weight.
MAX17035/MAX17435/MAX17535
DC-DC Converter
MAX17035/MAX17435/MAX17535 employ synchronous step-down DC-DC converter with n-channel, high-side MOSFET switch n-channel low-side synchronous rectifier. MAX17035/MAX17435/MAX17535 feature pseudo-fixed-frequency, current-mode control scheme with cycle-by-cycle current limit. controller's constant off-time (tOFF) calculated based VDCIN, VCSIN, time constant with minimum value 300ns. MAX17035/MAX17435/MAX17535 also operate discontinuous conduction mode improved light-load efficiency. operation DC-to-DC controller determined following five comparators shown functional diagram Figure IMIN comparator sets peak inductor current discontinuous mode. IMIN compares control signal (LVC) against 100mV (typ). When voltage less than 100mV, both low. CCMP comparator used current-mode regulation continuous conduction mode. CCMP compares against charging current feedback signal (CSI). comparator output high high-side MOSFET on-time terminated when voltage higher than LVC. IMAX comparator provides cycle-by-cycle current limit. IMAX compares (corresponding when 10mI). comparator output high high-side MOSFET on-time terminated when current-sense signal exceeds 10A. cycle cannot start until IMAX comparator output goes low. ZCMP comparator provides zero-crossing detection during discontinuous conduction. ZCMP compares current-sense feedback signal 500mA (RS2 10mI). When inductor current lower than 500mA threshold, comparator output high turned off.
comparator. MAX17035/MAX17435/ MAX17535 incorporate comparator check battery voltage 400mV above point and, that condition detected, disables charging. MAX17035/MAX17435/MAX17535 control input current (CCS control loop), charge current (CCI control loop), charge voltage (CCV control loop), depending operating condition. three control loops, CCV, CCI, brought together internally lowest voltage clamp (LVC) amplifier. output amplifier feedback control signal DC-DC controller. minimum voltage CCV, CCI, appears output amplifier clamps other control loops within 0.3V above control point. Clamping other control loops close lowest control loop ensures fast transition with minimal overshoot when switching between different control loops (see Compensation section). With sufficient charge current, MAX17035/MAX17435/ MAX17535s' inductor current never crosses zero, which defined continuous conduction mode. regulator switches 1.2MHz (nominal) dropout (VCSIN 0.88 VDCIN). controller starts cycle turning high-side MOSFET turning low-side MOSFET. When charge current feedback signal (CSI) greater than control point (LVC), CCMP comparator output goes high controller initiates off-time turning high-side MOSFET turning low-side MOSFET. operating frequency governed off-time dependent upon VCSIN VDCIN. fixed off-time, controller initiates cycle control point (LVC) greater than 150mV, peak charge current less than cycle-by-cycle current limit. Restated another way, IMIN
CCV, CCI, CCS, Control Blocks
Continuous Conduction Mode
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
must high, must low, must controller initiate cycle. peak inductor current exceeds IMAX comparator threshold output voltage exceeds threshold, then on-time terminated. cycle-by-cycle current limit effectively protects against overcurrent short-circuit faults. during off-time inductor current goes zero, ZCMP comparator output pulls high, turning low-side MOSFET. Both high- low-side MOSFETs turned until another cycle ready begin. MAX17035/MAX17435/MAX17535 enter into discontinuous conduction mode (see Discontinuous Conduction section). on-time calculated according following equation:
IRIPPLE VCSSN VBATT
GMOUT BATT
loop internally compensated. share external compensation capacitor. control loop, which dominant, uses external compensation that used uses internal compensation capacitor. Loop Compensation simplified schematic Figure sufficient describe operation MAX17035/MAX17435/ MAX17535 when voltage loop (CCV) control. required compensation network pole-zero pair formed with RCV, which internal 1.7kI. pole necessary roll voltage loop's response frequency; 330pF sufficient most applications.
Compensation
where:
IRIPPLE BATT
There 0.3Fs minimum off-time when (VDCIN VBATT) differential becomes small. VBATT 0.88 VDCIN, then threshold minimum off-time reached off-time fixed 0.27Fs. switching frequency this mode varies according equation: IRIPPLE VCSSN VBATT Discontinuous Conduction MAX17035/MAX17435/MAX17535 also operate discontinuous conduction mode ensure that inductor current always positive. MAX17035/ MAX17435/MAX17535 enter discontinuous conduction mode when output control point falls below 150mV. 10mI, this corresponds 375mA: 150mV IDIS 375mA where charge current 10mI. discontinuous mode, cycle started until voltage rises above 150mV. Discontinuous mode operation occur during conditioning charge overdischarged battery packs, when charge current been reduced sufficiently control loop, when charger constant-voltage mode with nearly full battery pack.
RESR COUT ROGMV
Figure Loop Diagram
outputs optimized driving moderate-sized power MOSFETs. MOSFET drive capability same both low-side highsides switches. This consistent with variable duty factor that occurs notebook computer environment where battery voltage changes over wide range. There must low-resistance, low-inductance path from driver MOSFET gate prevent shootthrough. Otherwise, sense circuitry MAX17035/ MAX17435/MAX17535 interprets MOSFET gate while there still charge left gate. very short, wide traces measuring squares squares less (1.25mm 2.5mm wide MOSFET 25mm from device). Unlike output, output uses 50ns (typ) delay time prevent low-side MOSFET from turning until fully off. same considerations should used routing signal high-side MOSFET.
MOSFET Drivers
High-Frequency, Low-Cost SMBus Chargers
high-side driver (DHI) swings from above (BST) typical impedance 1.5I sourcing 0.8I sinking. low-side driver (DLO) swings from DLOV ground typical impedance sinking sourcing. This helps prevent from being pulled when high-side switch turns capacitive coupling from drain gate low-side MOSFET. This places some restrictions MOSFETs that used. Using low-side MOSFET with smaller gate-to-drain capacitance prevent these problems. Generally, small high-side MOSFET desired reduce switching losses high input voltages. However, RDS(ON) required stay within package powerdissipation limits often limits small MOSFET optimum occurs when switching (AC) losses equal conduction (RDS(ON)) losses. Switching losses high-side MOSFET become insidious heat problem when maximum adapter voltages applied, squared term switchingloss equation. high-side MOSFET that chosen adequate RDS(ON) supply voltages becomes extraordinarily when subjected VIN(MAX), then choose MOSFET with lower losses. Calculating power dissipation switching losses difficult since must allow difficult quantifying factors that influence turn-on turn-off times. These factors include internal gate resistance, gate charge, threshold voltage, source inductance, layout characteristics. following switching-loss calculation provides only very rough estimate substitute breadboard evaluation, preferably including verification using thermocouple mounted PD(HS_Switching) VDCIN(MAX) ILOAD IGATE
MAX17035/MAX17435/MAX17535
Design Procedure
Choose n-channel MOSFETs according maximum required charge current. Low-current applications usually require less attention. high-side MOSFET (N1) must able dissipate resistive losses plus switching losses both VDCI;MIN) VDCIN(MAX). Calculate both these sums. Ideally, losses VDCIN(MIN) should roughly equal losses VDCIN(MAX) with lower losses between. losses VDCIN(MIN) significantly higher than losses VDCIN(MAX), consider increasing size Conversely, losses VDCIN(MAX) significantly higher than losses VIN(MIN), consider reducing size DCIN does vary over wide range, minimum power dissipation occurs where resistive losses equal switching losses. Choose low-side MOSFET that lowest possible on-resistance (RDS(ON)), comes moderate-sized package (i.e., 8-pin DPAK, PAK), reasonably priced. Make sure that gate driver supply sufficient current support gate charge current injected into parasitic gate-to-drain capacitor caused high-side MOSFET turning otherwise, cross-conduction problems occur. Select devices that have short turn-off times, make sure that: N2(tDOFF(MAX)) N1(tDON(MIN)) 40ns, N1(tDOFF(MAX)) N2(tDON(MIN)) 40ns Failure could result efficiency-reducing shootthrough currents. Worst-case conduction losses occur duty factor extremes. high-side MOSFET, worst-case power dissipation (PD) resistance occurs minimum supply voltage:
PD(High Side) BATT LOAD DS(ON) VDCIN
MOSFET Selection
where CRSS reverse transfer capacitance IGATE peak gate-drive source/sink current (3.3A sourcing sinking). low-side MOSFET (N2), worst-case power dissipation always occurs maximum input voltage:
PD(Low Side) BATT LOAD DS(ON) VDCIN
charge current, ripple, operating frequency (off-time) determine inductor characteristics. optimum efficiency, choose inductance according following equation: VBATT tOFF/(0.3 ICHG) This sets ripple current charge current results good balance between inductor size efficiency. Higher inductor values decrease ripple current. Smaller inductor values require high saturation current capabilities degrade efficiency. Inductor must have saturation current rating least maximum charge current plus ripple current (DIL): ISAT ICHG (1/2)
Inductor Selection
MOSFET Power Dissipation
High-Frequency, Low-Cost SMBus Chargers MAX17035/MAX17435/MAX17535
ripple current determined VBATT tOFF/L where: tOFF 2.5Fs (VDCIN VBATT)/ VDCIN VBATT 0.88 VDCIN tOFF 0.3Fs VBATT 0.88 VDCIN input capacitor must meet ripple current requirement (IRMS) imposed switching currents. Nontantalum chemistries (ceramic, aluminum, OSCON) preferred their resilience power-up surge currents: BATT (VDCIN VBATT IRMS VDCIN input capacitors should sized that temperature rise ripple current continuous conduction does exceed approximately 10NC. maximum ripple current occurs duty factor VDCIN VBATT, which equates ICHG. application interest does achieve maximum value, size input capacitors according worstcase conditions. output capacitor absorbs inductor ripple current must tolerate surge current delivered from battery when initially plugged into charger. such, both capacitance important parameters specifying output capacitor filter ensure stability DC-to-DC converter. Compensation section. Beyond stability requirements, often sufficient make sure that output capacitor's much lower than battery's ESR. Either tantalum ceramic capacitors used output. Ceramic devices preferable because their good voltage ratings resilience surge currents. most applications output 4.7FF. output voltage input voltage high, output capacitance need increased.
Applications Information
Bypass DCIN with 0.1FF ceramic ground (Figure protect MAX17035/MAX17435/ MAX17535 when power source input reversed. signal diode adequate because DCIN only powers internal reference. Bypass VCC, DCIN, LDO, DHI, VAA, shown Figure Good layout required achieve specified noise immunity, efficiency, stable performance. layout artist must given explicit instructions- preferably, sketch showing placement power switching components high current routing. Refer layout MAX17035/MAX17435/MAX17535 evaluation examples. ground plane essential optimum performance. most applications, circuit located multilayer board, full four more copper layers recommended. layer high current connections, bottom layer quiet connections, inner layers uninterrupted ground plane. following step-by-step guide: Place high-power connections first, with their grounds adjacent: Minimize current-sense resistor trace lengths, ensure accurate current sensing with Kelvin connections. Minimize ground trace lengths high-current paths. Minimize other trace lengths high-current paths. wide traces high-current paths. Connect high-side MOSFET (10mm length). Minimize node (MOSFETs, rectifier cathode, inductor (15mm length)). Keep side reduce radiation.
Layout Bypassing
Input Capacitor Selection
Output Capacitor Selection
High-Frequency, Low-Cost SMBus Chargers
Ideally, surface-mount power components flush against another with their ground terminals almost touching. These high-current grounds then connected each other with wide, filled zone top-layer copper, they through vias. resulting top-layer subground plane connected normal inner-layer ground plane paddle. Other highcurrent paths should also minimized, focusing primarily short ground current-sense connections eliminates about layout problems. Place signal components. Keep main switching node node) away from sensitive analog components (current-sense traces capacitor). Important: must further than 10mm from current-sense resistors. Quiet connections REF, CCV, CCI, ACIN, DCIN should returned separate ground (GND) island. appropriate traces marked schematic with ground symbol. There very little current flowing these traces, ground island need very large. When placed inner layer, sizable ground island help simplify layout because current connections made through vias. ground backside package should also connected this quiet ground island. Keep gate drive traces (DHI DLO) short possible 20mm), route them away from current-sense lines REF. These traces should also relatively wide 1.25mm). Place ceramic bypass capacitors close bulk capacitors placed further away. Place current-sense input filter capacitors under part, connected directly pin. single-point star ground placed directly below part PGND pin. Connect power ground (ground plane) quiet ground island this location. Refer MAX17035 layout layout example.
MAX17035/MAX17435/MAX17535
Chip Information
PROCESS: BiCMOS
PACKAGE TYPE TQFN
Package Information
latest package outline information land patterns, www.maxim-ic.com/packages. PACKAGE CODE T2444-4 DOCUMENT 21-0139
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