Adapter/USB Dual Input Single-cell Li-ion Charger POWER MANAGEMEN

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Adapter/USB Dual Input Single-cell Li-ion Charger POWER MANAGEMEN

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SC820
Adapter/USB Dual Input Single-cell Li-ion Charger
POWER MANAGEMENT Features
Dual input charger automatically selects adapter input over Constant voltage 4.2V, regulation Fast-charge current regulation 70mA, 700mA Three mode charging (current regulation, voltage regulation, thermal limiting) Input voltage protection Current-limited adapter charging support reduces power dissipation charger input limits charge current prevent Vbus overload Instantaneous CC-to-CV transition faster charging Programmable battery-dependent currents (adaptersourced fast-charge pre-charge, termination) Programmable source-limited currents (USB-sourced fast-charge pre-charge) Three termination options float-charge, automatic re-charge, forced re-charge keep battery topped-off after termination without float-charging Soft-start reduces adapter load transients High operating voltage range permits unregulated adapters Complies with CCSA YD/T 1591-2006 Space saving 2x2x0.6 (mm) MLPD package WEEE RoHS compliant
Description
SC820 dual input (adapter/USB) linear single-cell Li-ion battery charger lead MLPD ultra-thin package. Both inputs will survive sustained input voltage protect against plug overshoot faulty charging adapters. Charging begins automatically when valid input source applied either input. adapter input selected when both input sources present. Thermal limiting protects SC820 from excessive power dissipation when charging from either source. SC820 programmed turn when charging complete continue operating regulator while floatcharging battery. adapter input charges with adapter operating voltage regulation current limit obtain lowest possible power dissipation pulling input voltage down battery voltage. VUSB input automatically limits load current prevent over-loading Vbus supply. Charge current programming requires resistors. determines battery-capacity dependent currents: adapter input fast-charge current, pre-charge current, charge termination current. other independently determines input-limited charging currents: input fastcharge pre-charge current.
Applications
Mobile phones players handheld receivers
Typical Application Circuit
SC820
VADAPTER Vbus VUSB STATB IPRGM IPUSB Battery Pack Device Load
February 2008
2008 Semtech Corporation
SC820
Configuration Ordering Information
Device
SC820ULTRT(1)(2) SC820EVB
VIEW VUSB
Package
MLPD-UT-8 Evaluation Board
Notes: Available tape reel only. reel contains 3,000 devices. Lead-free package only. Device WEEE RoHS compliant.
STATB
IPRGM
IPUSB
MLPD-UT8; 2x2, LEAD 68°C/W
Marking Information
Date Code
SC820
Absolute Maximum Ratings
VUSB -0.3 +30.0 BAT, IPRGM, IPUSB -0.3 +6.5 STATB, -0.3 VBAT +0.3 Input Current VUSB Input Current BAT, IPRGM, IPUSB Short-to-GND Duration Continuous Total Power Dissipation Protection Level(1) (kV)
Recommended Operating Conditions
Operating Ambient Temperature (°C)
Thermal Information
Thermal Resistance, Junction Ambient(2) (°C/W) Junction Temperature Range (°C) +150 Storage Temperature Range (°C) +150 Peak Reflow Temperature (10s 30s) (°C) +260
Exceeding above specifications result permanent damage device device malfunction. Operation outside parameters specified Electrical Characteristics section recommended. NOTES: Tested according JEDEC standard JESD22-A114-B. Calculated from package still air, mounted (in), layer with thermal vias under exposed JESD51 standards.
Electrical Characteristics
Test Conditions: VVAD VVUSB 4.75V 5.25V; VBAT 3.7V; values 25°C; -40°C 85°C, unless specified.
Parameter
Operating Voltage Select Rising Threshold Deselect Falling Threshold Input Operating Voltage VUSB Select Rising Threshold VUSB Deselect Falling Threshold VUSB Select Hysteresis Rising Threshold Falling Threshold Hysteresis Charging Disabled Quiescent Current Charging Enabled Quiescent Current VUSB Charging Disabled Quiescent Current VUSB Charging Enabled Quiescent Current
Symbol
VAD-OP VTADsel-R VTADsel-F VUSB-OP VTUSBsel-R VTUSBsel-F VTUSBsel-H VTOVP-R VTOVP-F VTOVP-H IqVAD_DIS IqVAD_EN IqVUSB_DIS IqVUSB_EN
Conditions
4.60 4.30
5.00 4.45 2.85 5.00 4.20
8.20 4.60 3.00 8.20 4.35
Units
VVAD VBAT
2.70 4.35
VVUSB VBAT VVUSB VBAT VTUSBsel-R VTUSBsel-F VUSB input VUSB input (VTOVP-R VTOVP-F) VVUSB VENB VBAT VVUSB VENB excluding IBAT, IIPRGM, IIPUSB VVAD VENB VBAT VVAD VENB excluding IBAT, IIPRGM, IIPUSB 3.65
4.00
SC820
Electrical Characteristics (continued)
Parameter
VUSB Deselected Quiescent Current(3) Regulation Voltage
Symbol
IqVUSB_DES VCV_LOAD VTReQ VTPreQ lBAT_V0
Conditions
VVAD VVUSB IBAT 50mA, -40°C 125°C Relative 50mA, VVAD VVUSB VVAD IBAT 700mA, -40°C 125°C
4.24
Units
4.16
4.20
Voltage Load Regulation(4)
Re-charge Threshold Pre-charge Threshold (rising)
VBAT
2.85
2.90
2.95 29.4
VBAT VCV, VVAD VVUSB VBAT VCV, VVAD VVUSB VENB VBAT VCV, VVAD VVUSB connected 2.05 RIPRGM 2.94k, VTPreQ VBAT RIPRGM 2.94k, 1.8V VBAT VTPreQ RIPRGM 2.94k, VBAT IBAT 700mA, 125°C 2.05 RIPUSB 4.42k, VTPreQ VBAT RIPUSB 4.42k, 1.8V VBAT VTPreQ IBAT 500mA, 125°C VVAD 5.0V, VVUSB VTPreQ VBAT VBAT VTPreQ VBAT (either input selected) VVAD VTPreQ VBAT VVAD VBAT VTPreQ VUSB supply current limit 500mA, VVAD RIPUSB 3.65k (559mA) 4.45
Battery Leakage Current
lBAT_DIS lBAT_MON
IPRGM Programming Resistor Fast-Charge Current, input Pre-Charge Current, input Termination Current, either input Dropout Voltage IPUSB Programming Resistor Fast-Charge Current, VUSB input Pre-Charge Current, VUSB input VUSB Dropout Voltage IPRGM Fast-charge Regulated Voltage IPRGM Pre-charge Regulated Voltage IPRGM Termination Threshold Voltage IPUSB Fast-charge Regulated Voltage IPUSB Pre-charge Regulated Voltage VUSB Under-Voltage Load Regulation Limiting Voltage
RIPRGM IFQ_AD IPreQ_AD ITERM VDO_AD RIPUSB IFQ_USB IPreQ_USB VDO_USB VIPRGM_FQ VIPRGM_PQ VTIPRGM_TERM VIPUSB_FQ VIPUSB_PQ VVUSB_UV_LIM
0.75
29.4
0.55 2.04 0.408 0.204 2.04 0.408
4.58
4.70
SC820
Electrical Characteristics (continued)
Parameter
Thermal Limiting Threshold Temperature Thermal Limiting Rate Input High Voltage Input Voltage Input Voltage Input High-range Threshold Input Current Input High-range Sustain Input Current Input Mid-range Load Limit Input Low-range Input Current Input Leakage STATB Output Voltage STATB Output High Current
Symbol
IIH_TH
Conditions
Units
current required pull from floating midrange into high range Current required hold high range, VENB VBAT, VBAT 4.2V Input will float range when this load limit observed. VENB VVIN VENB VBAT 4.2V ISTAT_SINK VSTAT
IIH_SUS
IILEAK VSTAT_LO ISTAT_HI
Notes: Maximum operating voltage maximum Vsupply defined EIA/JEDEC Standard paragraph 2.11. This input voltage which charger guaranteed begin operation. Sustained operation VTADsel-F VVAD guaranteed only current limited charging source applied pulled below VTADsel-R charging load; forced voltage below VTADsel-R some cases result regulation errors other unexpected behavior. selected input VVAD VVUSB, such when operating with adapter current limit while VUSB charging source applied, IqVUSB_DES will increase approximately IqVUSB_EN. load currents exceeding 700mA, 700mA while elevated ambient temperature, charger enter dropout with input before battery voltage risen VCV. specification VDO_AD. Although this safe acceptable mode operation, specification when dropout applicable; higher input voltage will restore charger regulation these cases. Note that VBAT always less than while dropout. battery state-of-charge increases, charging current will decrease allowing battery voltage rise VCV, regulation will begin. This appears softening rounding CC-to-CV regulation mode transition, similar that seen chargers with linear CC-to-CV regulation crossover.
SC820
Typical Characteristics
Line Regulation
IBAT 50mA 4.204 4.204
Load Regulation
VVAD
4.196
4.196
VBAT
VBAT
4.192
4.192
4.188
4.188
4.184
4.184
4.18
4.18
VVAD
IBAT (mA)
Temperature Regulation
VVAD IBAT 50mA 4.204 4.196
Line Regulation USB)
VBAT 3.7V
RIPRGM RIPUSB 2.94k
IBAT (mA)
VBAT
4.192
4.188
4.184
RIPRGM RIPUSB 4.42k
4.18
Ambient Temperature
VVAD
VBAT Regulation USB)
VVAD
Temperature Regulation USB)
VVAD VBAT 3.7V
RIPRGM RIPUSB 2.94k
IBAT (mA)
RIPRGM RIPUSB 4.42k
IBAT (mA)
VBAT
Ambient Temperature
SC820
Typical Characteristics (continued)
Line Regulation USB)
VBAT 2.6V RIPRGM RIPUSB 2.94k
Temperature Regulation USB)
VVAD VBAT 2.6V
RIPRGM RIPUSB 2.94k
IBAT (mA)
IBAT (mA)
RIPRGM RIPUSB 4.42k
RIPRGM RIPUSB 4.42k
VVAD
Ambient Temperature
FQ_AD IPRGM VVAD VBAT 3.7V,
1000
IFQ_USB RIPUSB
PQ_AD IPRGM VVAD VBAT 2.6V,
IPQ_USB RIPUSB
IBAT (mA)
IBAT (mA)
RIPRGM RIPUSB
RIPRGM RIPUSB
Input Reselection,
VBAT=3.7V, VVUSB=5.0V
Input Reselection,
VBAT=3.7V, VVUSB=5.0V
VVAD (1.0V/div)
VVAD (1.0V/div)
IBAT (200mA/div) IBAT (200mA/div)
VVAD=0V- IBAT=0mA- 400s/div
VVAD=0V- IBAT=0mA- 400s/div
SC820
Typical Characteristics (continued)
Charging Cycle Battery Voltage Current
850mAhr battery, RIPRGM 2.94k, VVAD 5.0V,
Pre-Charging Battery Voltage Current
850mAhr battery, RIPRGM 2.94k, VVAD 5.0V, IBAT VBAT 2.75 2.25
VBAT (V), Internal Power Dissipation
VBAT IBAT
3.75 3.25
IBAT (mA)
2.25
0.25
0.75
1.25
1.75
Time (hrs)
Time
CC-to-CV Battery Voltage Current
850mAhr battery, RIPRGM 2.94k, VVAD 5.0V, 4.21
Re-Charge Cycle Battery Voltage Current
850mAhr battery, RIPRGM 2.94k, VVAD 5.0V, Load 10mA VBAT IBAT Discharge hours omitted.
VBAT (V), Internal Power Dissipation
IBAT
IBAT (mA)
4.18 VBAT 4.17
4.16
44.5
45.5
46.5
47.5
Time (min)
Time (hrs)
IBAT (mA)
VBAT
4.19
IBAT (mA)
VBAT
SC820
Descriptions
Name
VUSB
Function
Supply connect charging adapter. This protected against damage high voltage 30V. Supply connect Vbus power. Typically limited load-current input. This protected against damage high voltage 30V. Status output This open-drain asserted (pulled low) when valid charging supply connected either VUSB, charging cycle begins. released when termination current reached, indicating that charging complete. STATB asserted re-charge cycles. Ground Fast-charge pre-charge current programming VUSB power source VUSB fast-charge current programmed connecting resistor from this ground. VUSB pre-charge current fast-charge current. Fast-charge pre-charge current programming adapter power source fast-charge current programmed connecting resistor from this ground. pre-charge current fast-charge current. charging termination current threshold (for either VUSB input selection) IPRGM programmed fast-charge current. Charger output
STATB
IPUSB
IPRGM
connect battery positive terminal.
Combined device enable/disable Logic high disables device. enable charging with indefinite float-charging. Float this enable charging without float-charge upon termination. Note that this must grounded SC820 operated without battery connected BAT. heatsinking purposes connected internally. Connect exposed ground plane using multiple vias.
Thermal
SC820
Block Diagram
V_Adapter USB_VBUS
VUSB
Input Selection Logic Adapter/USB select
VVUSB_UV_LIM 4.575V
Connect regulated supply
4.2V
System Load
VIREF LithiumIon Single Cell Battery Pack
Temperature VT_CT Thermal Limiting
Feedback Selection
STATB Pre-charge, Termination Controller, Logical State Machine Termination VTIPRGM_TERM VTENB_HIGH ~1.50V Tri-level Control VTENB_LOW ~0.55 IPUSB IPRGM
RIPUSB
RIPRGM
SC820
Applications Information
Charger Operation
SC820 dual-input stand-alone Li-ion battery charger. input optimized charging adapter. VUSB optimized charging from Vbus supply. device independently programmed battery-capacity-dependent currents (adapter fast-charge current termination current) using IPRGM pin. Charging currents from Vbus supply, which maximum load specification, programmed using IPUSB pin. When input supply first detected, charge cycle initiated STATB open-drain output goes low. battery voltage less than pre-charge threshold voltage, pre-charge current supplied. Pre-charge current programmed fast-charge current selected input. When battery voltage exceeds pre-charge threshold, typically within seconds standard battery with starting cell voltage greater than fast-charge Constant Current (CC) mode begins. charge current soft-starts three steps (20%, 60%, 100% programmed fast-charge current) reduce adapter load transients. current programmed IPRGM resistance ground when input selected IPUSB resistance ground when VUSB input selected. charger begins Constant Voltage (CV) regulation when battery voltage rises fully-charged singlecell Li-ion regulation voltage (VCV nominally 4.2V. regulation, output voltage regulated, battery charges, charge current gradually decreases. STATB output goes high when IBAT drops below termination current threshold, which IPRGM programmed fast-charge current regardless input selected. This known charge termination. matically process repeats. forced re-charge cycle also periodically commanded processor keep batter topped-off without float-charging. Monitor State section details. Re-charge cycles indicated STATB pin.
Charging Input Selection
SC820 charging supply input pins. optimized adapter charging. VUSB optimized charging from Vbus power supply. inputs differ selection rising deselection falling thresholds, their behavior when overloading their respective charging sources, which current programming determines fast-charge pre-charge current. Both same Over-Voltage Protection (OVP) threshold. Glitch filtering performed VUSB inputs, applied input voltage that ringing across selection threshold will selected until ringing ceased. When both inputs exceed their respective UVLO thresholds, selected even when voltage applied while already charging from VUSB input. also selected case that voltage exceeds threshold, that excessive voltage will disable charging despite presence valid VUSB input voltage. When valid input (defined greater than selection threshold less than threshold) first selected, charge cycle initiated STATB output asserted. When input selection made (when applied removed while VUSB present), charge cycle immediately halted re-initiated with newly selected input. There momentary (approximately 1ms) interruption output current release -assertion STATB during input reselection. input charging current loads adapter beyond current limit, input voltage will pulled down just above battery voltage. adapter input deselection falling threshold close battery voltage pre-charge threshold permit lowdissipation charging from current limited adapter. VUSB input provides higher deselection falling threshold appropriate specification.
Optional Float-charging Monitoring
Depending state input, upon termination SC820 either operates indefinitely voltage regulator (float-charging) turns output. output turned upon termination, device enters monitor state. this state, output remains until voltage decreases re-charge threshold (VTReQ). re-charge cycle then begins auto-
SC820
Applications Information (continued)
input also provides Under-Voltage Load Regulation (UVLR), which charging current reduced needed prevent overloading Vbus supply. UVLR serve low-cost alternative directly programming power charge current. also useful where there signal available indicate whether high power mode should selected. input, nominally. input designed lower dropout voltage high current, which ensures charging without thermal limiting with charging adapter operating current limit least 700mA. Current regulation accuracy dominated gain error high current settings offset error current settings. range expected fast-charge output current versus programming resistance RIPRGM RIPUSB (for VUSB input selected, respectively) shown Figures figures show nominal current versus nominal RIPRGM RIPUSB resistance center plot theoretical limit plots indicating maximum minimum current versus nominal programming resistance. These plots derived from models expected worst-case contribution error sources depending programmed current. current range includes uncertainty tolerance resistors. dots each plot indicate currents obtained with standard value tolerance resistors. Figures show high resistance ranges, respectively.
Constant Current Mode Fast-charge Current Programming
Constant Current (CC) mode active when battery voltage above pre-charge threshold voltage (VTPreQ) less than VCV. When selected input, programmed regulation fast-charge (FQ) current inversely proportional IPRGM resistance according equation
When VUSB selected input, programmed mode fast-charge current inversely proportional IPUSB resistance according equation
Pre-charge Mode
This mode automatically enabled when battery voltage below pre-charge threshold voltage (VTPreQ). Pre-charge current conditions battery fast charging. pre-charge current value fixed nominally fast-charge current selected input. fast-charge current programmed
fast-charge current programmed minimum 70mA maximum 995mA either
1100 1050 1000
Fast-charge Current (mA)
Fast-charge Current (mA)
RIPRGM RIPUSB (k), R-tol
RIPRGM RIPUSB (k), R-tol
Figure Fast-charge Current Tolerance versus Programming Resistance, Resistance Range
Figure Fast-charge Current Tolerance versus Programming Resistance, High Resistance Range
SC820
Applications Information (continued)
resistance between IPRGM input, resistance between IPUSB VUSB input. Pre-charge current regulation accuracy dominated offset error. range expected pre-charge output current versus programming resistance shown Figures figures show nominal pre-charge current versus nominal resistance center plot theoretical limit plots indicating maximum minimum current versus nominal programming resistance. These plots derived from models expected worst-case contribution error sources depending programmed current. current range includes uncertainty tolerance resistors. dots each plot indicate currents obtained with standard value tolerance resistors. Figures show high resistance ranges, respectively. termination current threshold fixed input fast-charge current, programmed resistance between IPRGM GND. IPRGM resistance determines termination current threshold regardless whether selected charging input VUSB. Charger output current battery charge current system load current. Battery charge current changes gradually, establishes slowly diminishing lower bound output current while charging mode. load current into typical digital system highly transient nature. Charge cycle termination detected when battery charging current greatest load current occurring within immediate 300s 550s past interval less than programmed termination current. This timing behavior permits charge cycle termination occur during brief low-load-current interval, does require that longer interval average load current small. Termination current threshold accuracy dominated offset error. range expected termination current versus programming resistance RIPRGM (for either VUSB input selected) shown Figures figures show nominal termination current versus nominal RIPRGM resistance center plot theoretical limit plots indicating maximum minimum current versus nominal programming resistance. These
Termination
When battery voltage reaches VCV, SC820 transitions from constant current regulation constant voltage regulation. While VBAT regulated VCV, current into battery decreases battery becomes fully charged. When output current drops below termination current threshold, charging terminates. Upon termination, STATB open drain output turns charger either enters monitor state floatcharges battery, depending logical state input pin.
Pre-charge Current (mA)
Pre-charge Current (mA)
RIPRGM RIPUSB (k), R-tol
RIPRGM RIPUSB (k), R-tol
Figure Pre-charge Current Tolerance versus Programming Resistance, Resistance Range
Figure Pre-charge Current Tolerance versus Programming Resistance, High Resistance Range
SC820
Applications Information (continued)
Termination Current Threshold (mA)
Termination Current Threshold (mA)
RIPRGM (k), R-tol
RIPRGM (k), R-tol
Figure Termination Current Tolerance versus Programming Resistance, Resistance Range plots derived from models expected worst-case contribution error sources depending programmed current. current range includes uncertainty tolerance resistor. dots each plot indicate currents obtained with standard value tolerance resistors. Figures show high resistance ranges, respectively.
Figure Termination Current Tolerance versus Programming Resistance, High Resistance Range equivalent circuit looking into variable resistance, minimum 15k, approximately source. input will float range whenever external driver sinks sources less than common worst-case characteristic high impedance weak pull-up pull-down GPIO configured input. driving GPIO must able sink source least ensure high state, respectively, although drive current typically less. (See Electrical Characteristics table.) input voltage permitted float mid-range, charger enabled will turn output following charge termination will enter monitor state. This state explained next section. Mid-range selected either floating input (sourcing sinking less than being externally forced such that VENB falls within midrange limits specified Electrical Characteristics table. When driven (VENB VIL), charger enabled will continue float-charge battery following termination. charger already monitor state following previous termination, will exit monitor state begin float-charging. When driven high (VENB VIH), charger disabled input enters high impedance state, suspending tri-level functionality. specified high level input current required only until high
Enable Input
tri-level logical input that allows selection following behaviors:
Charging enabled with float-charging after termination (ENB range) Charging enabled with float-charging disabled battery monitoring termination (ENB range) Charging disabled (ENB high range).
This input designed interface processor GPIO port powered from peripheral supply voltage 1.8V high fully charged battery. While connected GPIO port configured output, processor writes select low-range, select highrange. GPIO port configured input select mid-range. also permanently grounded select lowrange left unconnected select mid-range will necessary change level selection.
SC820
Applications Information (continued)
level recognized SC820 internal logic. trilevel float circuitry then disabled input becomes high impedance. Once forced high, will float range. restore tri-level operation, must first pulled down range least VENB VIM), then, desired, released reconfiguring GPIO input) select mid-range. GPIO weak pull-down when configured input, then unnecessary drive restore tri-level operation; simply configure GPIO input. When selection changes from high-range midor low-range, charge cycle begins STATB goes low. Note that GPIO with weak pull-up input configuration used, pull-up current will flow from GPIO into while floating mid-range. Since GPIO driving equivalent voltage source through resistance (looking into ENB), this current small possibly less than Nevertheless, this current drawn from GPIO peripheral power supply and, therefore, from battery after termination. (See next section, Monitor State.) this reason, preferable that GPIO chosen operate should provide true high impedance (CMOS) configuration weak pull-down when configured input. When pulled below float voltage, output current sourced from VUSB, from battery. current becomes less than termination current, charging terminates. SC820 turns charging output returns monitor state within millisecond. This forced re-charge behavior useful periodically testing battery state-of-charge topping-off battery, without float-charging without requiring battery discharge automatic re-charge voltage. should held least ensure successful forced re-charge. Forced re-charge requested time during charge cycle, even with charging source present, with detrimental effect charger operation. This allows host processor schedule forced re-charge desired interval, without regard whether charge cycle already progress, even whether charging source present. Forced re-charge will neither assert release STATB output.
Status Output
STATB open-drain output. asserted (driven low) charging begins after valid charging source connected voltage either input between selection limits. STATB also asserted charging begins after input returns either enable voltage ranges (mid voltage) from disable range. STATB subsequently released when termination current reached indicate endof-charge, when input driven high disable charging, when neither charging input selected valid charge. battery already fully charged when charge cycle initiated, STATB asserted approximately 750s before being released. STATB asserted automatic re-charge cycles. STATB connected interrupt input notify host controller charging status used driver.
Monitor State
floating, charger output STATB will turn device will enter monitor state when charge cycle complete. battery voltage falls below re-charge threshold (VCV VReQ) while monitor state, charger will automatically initiate recharge cycle. battery leakage current during monitor state more than over temperature typically less than 0.1A room temperature. While monitor state, tri-level input remains fully active, although midrange, sensitive both high levels. SC820 forced from monitor state float-charging) directly floatcharging operation driving low. This operation will turn charger output, will assert STATB output. again allowed float midrange, charger will remain only until output
Logical CC-to-CV Transition
SC820 differs from monolithic linear single cell Li-ion chargers that implement linear transition from regulation. linear transition method uses simultaneous feedback signals output voltage output current closed-loop controller. When output voltage sufficiently below regulation voltage, influence voltage feedback negligible
SC820
Applications Information (continued)
output current regulated desired current. battery voltage approaches regulation voltage (4.2V), voltage feedback signal begins influence control loop, which causes output current decrease although output voltage reached 4.2V. output voltage limit dominates controller when battery reaches 4.2V eventually controller entirely regulation. soft transition effectively reduces charge current below that which permitted portion charge cycle, which increases charge time. SC820, logical transition implemented from recover charge current lost soft transition. controller regulates only current until output voltage exceeds transition threshold voltage. then switches regulation. transition voltage from regulation typically higher than regulation voltage, which provides sharp clean transition free chatter between regulation modes. difference between transition voltage regulation voltage termed CC/CV overshoot. While regulation, output current sense remains active. output current exceeds programmed fastcharge current, controller reverts current regulation. logical transition from results fastest possible charging cycle that compliant with specified current voltage limits Li-ion cell. output current constant limit, then decreases abruptly when output voltage steps from overshoot voltage regulation voltage transition control. where voltage difference between pin. However, computed this exceeds then thermal limiting will become active thermal limiting regulation junction temperature will TJTL I(TJTL) where I(TJTL) (TJTL TL). Combining these equations solving TJTL, steady state junction temperature during active thermal limiting
TJTL
Although thermal limiting controller able reduce output current zero, this does happen practice. Output current reduced I(TJTL), reducing power dissipation such that temperature equilibrium TJTL reached. While thermal limiting active, charger functions remain active charger logical state preserved.
Operating Charging Adapter Current Limit
high charging current applications, charger power dissipation greatly reduced operating charging adapter current limit. SC820 input supports adapter-current-limited charging with deselection falling threshold with internal circuitry designed input voltage operation. operate adapter current limit, RIPRGM chosen such that adapter input programmed fast-charge current IFQ_AD exceeds current limit charging adapter IAD-LIM. Note that IAD-LIM less than IFQ_AD, then adapter voltage pulled down battery voltage while battery voltage below pre-charge threshold. this case, care must taken ensure that adapter will maintain current limit below IFQ_AD least until battery voltage exceeds pre-charge threshold. Failure could permit charge current exceed
Thermal Limiting
Device thermal limiting third output constraint Constant Current, Constant Voltage, "Constant" Temperature (CC/CV/CT) control. This feature permits higher input threshold, thus higher voltage poorly regulated adapters. high input voltage results excessive power dissipation, output current reduced prevent overheating SC820. thermal limiting controller reduces output current junction temperature When thermal limiting inactive,
SC820
Applications Information (continued)
pre-charge current while battery voltage below pre-charge threshold. This because input voltage will also compress pre-charge threshold internal reference voltage below battery voltage. This will prematurely advance charger logic from precharge current regulation fast-charge regulation, charge current will exceed safe level recommended pre-charge conditioning. deselection falling threshold (VTADsel-F) permits adapter voltage pulled down just above battery voltage charging load whenever adapter current limit less than programmed fastcharge current. SC820 should operated with adapter voltage below rising selection threshold (VTADSel-R) only input voltage result adapter current limiting. This implies that voltage first exceeds VTADsel-R begin charging, subsequently pulled down just above battery voltage charging load. Interaction Thermal Limiting Current Limited Adapter Charging permit charge current limited adapter, necessary that adapter input fast-charge current programmed greater than maximum adapter current, (IAD-LIM). this configuration, regulator will operate with pass device fully saturation, also called "dropout"). voltage drop from determined product minimum RDS-ON pass device multiplied adapter supply current. dropout, power dissipation SC820 PILIM (minimum RDS-ON) (IAD-LIM)2. Since minimum RDS-ON does vary with battery voltage, dropout power dissipation constant throughout portion charge cycle while adapter remains current limit. SC820 junction temperature will rise above ambient PILIM device temperature rises temperature which thermal limiting control loop limits charging current (rather than current being limited adapter), input voltage will rise adapter regulation voltage. power dissipation will increase that thermal limit regulation will further limit charge current. This will keep adapter voltage regulation remainder charge cycle. ensure that adapter remains current limit, internal device temperature must never rise This implies that must kept small enough ensure that (PILIM
VUSB Under-Voltage Load Regulation
VUSB UVLR prevents battery charging current from overloading Vbus network, regardless programmed fast-charge value. When VUSB input selected, SC820 monitors input voltage (VVUSB) reduces charge current necessary keep VVUSB above UVLR limit (VVUSB_UV_LIM). UVLR operates like fourth output constraint (along with constraints), active only when VUSB input selected. VUSB voltage externally pulled below VUSB_UV_LIM while input absent, UVLR feature will reduce charging current zero. This condition will interpreted termination will result end-ofcharge indication. STATB will remain asserted charging continuing. This prevents repetitive indications end-of-charge alternating with start-of-charge case that external VUSB load removed intermittent.
Short Circuit Protection
SC820 tolerate short circuit ground indefinitely. current into ground short approximately 10mA. During charging, short ground applied active current programming (IPRGM IPUSB) detected, while short ground inactive programming ignored. Pin-short detection active current programming forces SC820 into reset, turning output. pin-short either programming will prevent startup regardless charging input selected. When IPRGM IPUSB pin-short condition removed, charger begins normal operation automatically without input power cycling.
Over-Current Protection
Over-current protection provided modes operation, including regulation. output current limited either pre-charge fast-charge current
SC820
Applications Information (continued)
programmed IPRGM IPUSB, determined input selection), depending voltage output. ment. this experiment, final steady-state current 462mA SC820 evaluation board. fast thermal limiting feature ensures compliance with CCSA YD/T 1591-2006, Telecommunication Industrial Standard People's Republic China Technical Requirements Test Method Charger Interface Mobile Telecommunication Terminal, Section 4.2.3.1.
Input Over-Voltage Protection
VUSB input pins protected from overvoltage least above GND. When voltage selected input exceeds Over-Voltage Protection (OVP) rising threshold (VTOVP-R), charging halted. When input voltage falls below falling threshold (VTOVP-F), charging resumes. Note that input remains selected even case that voltage exceeds threshold. excessive voltage will disable charging despite presence valid VUSB voltage. fault turns STATB output. STATB turned again when charging restarts. threshold been relatively high permit poorly regulated adapters. Such adapters output high voltage until loaded charger. too-low threshold could prevent charger from ever turning loading adapter lower voltage. adapter voltage remains high despite charging load, fast thermal limiting feature will immediately reduce charging current prevent overheating SC820. This behavior illustrated Figure which VBAT 3.0V, 700mA, VVAD stepped from 8.1V. Initially, power dissipation SC820 3.6W.
VVAD=8.1V, VBAT=3.0V IBAT=700mA (Initially), PDISSIPATION=3.6W (Initially) IBAT (100mA/div)
Operation Without Battery
SC820 operated 4.2V regulator without battery present, example, factory testing. this anticipated, output capacitance should least 2.2F ensure stability. operate charger without battery, must driven grounded.
Capacitor Selection
cost, ceramic capacitors such dielectric material types recommended. capacitor range 22F. VUSB input capacitors typically between 0.1F 2.2F, although larger values will degrade performance. Capacitance must evaluated expected bias voltage, rather than zero-volt capacitance rating.
Layout Considerations
Layout linear devices critical switching regulator. However, careful attention detail will ensure reliable operation.
VVAD (2V/div)
VBAT (2V/div)
VVAD ,VBAT=0V- IBAT=0mA- 1s/div
Figure Thermal Limiting Example Notice output current rapidly reduced limit internal temperature, then continues decline circuit board gradually heats further reducing conduction heat from ambient environ-
Place input output capacitors close device optimal transient response device behavior. Connect ground connections directly ground plane. there ground plane, connect common local ground point before connecting board ground near pin. Attaching part larger copper footprint will enable better heat transfer from device, especially PCBs with internal ground power planes.
Design Considerations Charging
specification restricts load Vbus power network 100mA power devices
SC820
Applications Information (continued)
high power devices prior granting permission high power operation. specification restricts Vbus load 500mA high power devices after granting permission operate high power device. This suggests that fixed ratio power high power charging current desirable. this result suboptimal charging when battery capacity small permit fast charging 500mA. example, 250mAh battery will typically require fast-charge current 250mA less. fixed ratio high power charging will unnecessarily reduce charging current 50mA, well below 100mA permitted. arbitrary ratio low-to-high power charging currents obtained using external n-channel operated with processor GPIO signal engage second parallel IPUSB resistor. external circuit illustrated Figure
IPUSB RIPUSB_HI Hi/Lo Power Select RIPUSB
this event. While unlikely harm, this effect must also considered. purposes design dual-input adapter/USB charging, small battery with desired fast-charge current less than 500mA. 300mAh battery with maximum fast-charge current 300mA example. adapter input input high power fast-charge currents should both 300mA max. input power fast-charge current 100mA max. Refer circuit Figure data Figures IFQ_AD 300mA max, RIPRGM 7.50k. fixed IPUSB resistor RIPUSB 23.2k programs IFQ_USB 100mA max. When parallel resistor RIPUSB_HI 11.0k switched equivalent IPUSB resistor 7.50k, IFQ_USB 300mA max. large battery battery with desired fast-charge current exceeding 500mA. Large battery charging most consistent with fixed current ratio low-to-high power model operation. example, consider 800mAh battery, with maximum fast-charge current 800mA. adapter input fast-charge should configured 800mA (RIPRGM 2.80k), power fast-charge 100mA (RIPUSB 23.2k), high power fast- charge 500mA (RIPUSB_HI 5.62k).
Figure External programming arbitrary high power power charge currents. power mode charging, external transistor turned off. transistor turned when high power mode desired. effect switched parallel IPUSB resistor reduce effective programming resistance thus raise fast-charge current. open-drain GPIO used directly engage parallel resistor RIPUSB_HI. Care must taken ensure that RDS-ON GPIO considered selection RIPUSB_HI. Also important part-to-part temperature variation GPIO RDS-ON, their contribution High Power charge current tolerance. Note also that IPUSB will pulled briefly high during startup check IPUSB static pinshort ground. small amount current could, potentially, flow from IPUSB into GPIO structure through RIPUSB_HI during
Power Mode Alternative
Where mode selection signal available, where system cost board space make power mode external current programming impractical, power charging supported indirectly. IPUSB resistance selected obtain desired high power charge current. VUSB UVLR feature ensures that charging load will never pull Vbus supply voltage below VUSB_UV_LIM regardless host supply limit. UVLR limit voltage guarantees that voltage Vbus supply will loaded below power voltage specification limit, seen other power devices connected same host hub.
SC820
Outline Drawing MLPD-UT8
DIMENSIONS INCHES MILLIMETERS .020 .024 0.50 0.60 .000 .002 0.00 0.05 (.006) (0.1524) .007 .010 .012 0.18 0.25 0.30 .075 .079 .083 1.90 2.00 2.10 .061 .067 .071 1.55 1.70 1.80 .075 .079 .083 1.90 2.00 2.10 .026 .031 .035 0.65 0.80 0.90 .020 0.50 .012 .014 .016 0.30 0.35 0.40 .003 0.08 .004 0.10
INDICATOR (LASER MARK)
SEATING PLANE
NOTES: CONTROLLING DIMENSIONS MILLIMETERS (ANGLES DEGREES).
COPLANARITY APPLIES EXPOSED WELL TERMINALS.
SC820
Land Pattern MLPD-UT8
DIMENSIONS INCHES (.077) .047 .067 .031 .020 .006 .012 .030 .106 MILLIMETERS (1.95) 1.20 1.70 0.80 0.50 0.15 0.30 0.75 2.70
NOTES: CONTROLLING DIMENSIONS MILLIMETERS (ANGLES DEGREES). THIS LAND PATTERN REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES MET. THERMAL VIAS LAND PATTERN EXPOSED SHALL CONNECTED SYSTEM GROUND PLANE. FAILURE COMPROMISE THERMAL AND/OR FUNCTIONAL PERFORMANCE DEVICE.
Contact Information
Semtech Corporation Power Management Products Division Flynn Road, Camarillo, 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com

Adapter/USB Dual Input Single-cell Li-ion Charger POWER MANAGEMEN

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