SOT23, Single-Cell Battery Charger Current-Limited Supply Small 6

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SOT23, Single-Cell Battery Charger Current-Limited Supply Small 6

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19-1662; 10/00
SOT23, Single-Cell Battery Charger Current-Limited Supply
Small 6-Pin SOT23 Package Stand-Alone µP-Controlled Operation 0.5% Voltage Set-Point Accuracy Lowest Power Dissipation 4.7V Input Voltage Top-Off Charging Achieve Full Battery Capacity Inductor Required Safely Precharges Near-Dead Cells Automatic Power-Down when Input Power Removed
MAX1736
MAX1736 simple, low-cost, single-cell lithiumion (Li+) battery charger small hand-held applications. When accompanied current-limited voltage source (such wall cube), MAX1736 provides simple, accurate charging termination control single-cell batteries. MAX1736EUT42 preset 4.2V battery regulation voltage, while MAX1736EUT41 preset 4.1V. MAX1736 initiates charging four ways: battery insertion, charger power-up, battery voltage threshold, external manipulation pin. device features internal precharge current source that safely charges near-dead cells, well input-supply detection that shuts down MAX1736 when supply removed minimize battery current drain. MAX1736 accepts input voltages 22V, making compatible with wide range input supplies. single control input offers stand-alone microprocessor-controlled operation. MAX1736 packaged small SOT23-6 package. evaluation kit) available reduce design time.
Ordering Information
PART MAX1736EUT42-T MAX1736EUT41-T TEMP. RANGE PINPACKAGE MARK AAHO AANC
_Applications
Single-Cell Portable Applications Wireless Handsets Personal Digital Assistants Digital Cameras Small Hand-Held Equipment Self-Charging Battery Packs Cradle Chargers
-40°C +85°C SOT23-6 -40°C +85°C SOT23-6
Note: Requires special solder temperature profile described Absolute Maximum Ratings Section.
Typical Operating Circuit
CURRENT-LIMITED VOLTAGE SOURCE PFET
Configuration
VIEW
BATT
GATE BATT BATTERY MAX1736
GATE
MAX1736
SOT23
Maxim Integrated Products
price, delivery, place orders, please contact Maxim Distribution 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
SOT23, Single-Cell Battery Charger Current-Limited Supply MAX1736
ABSOLUTE MAXIMUM RATINGS
GATE GND.-0.3V +26V Operating Temperature Range .-40°C +85°C BATT, .-0.3V Storage Temperature Range .-65°C 150°C GATE IN.-6V +0.3V Maximum Junction Temperature 150°C GATE Continuous Current.-10mA +10mA Lead Temperature (soldering, 10s) (Note .+300°C Continuous Power Dissipation +70°C) (Note 6-Pin SOT23 (derate 8.1mW/°C above +70°C) .0.65W Note Thermal properties specified with product mounted board with square-inch copper area still air. Note This device constructed using unique packaging techniques that impose limit termal profile device exposed during solder attach rework. This limit permits only solder profiles recommended industry standard specification, IPC/JEDEC J-STD-020A, paragraph 7.6, Table IR/VPR Convention reflow. Pre-heating required. Hand wave soldering allowed.
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
(VIN 10V, VBATT 4.2V MAX1736EUT42 4.1V MAX1736EUT41, +85°C. Typical values +25°C, unless otherwise noted.) (Note
PARAMETER Input Voltage (Note Fast-Charge BATT Qualification Threshold Fast-Charge BATT Qualification Threshold Hysteresis BATT Regulation Voltage BATT Removal Detection Threshold BATT Removal Detection Threshold Hysteresis BATT Input Current, Input Power Removed BATT Input Current, Charger Disabled BATT Input Current, When Charging Precharge Source Current Input Current Detection Interval (Note GATE Source/Sink Current GATE Drive Source Current Battery Removal Minimum BATT Bypass Capacitance (Note Logic High Threshold Logic Threshold Pulldown Current
CONDITIONS External P-MOSFET BATT rising, transition from precharge fast charge
UNITS
2.65
MAX1736EUT42 MAX1736EUT41 BATT rising
4.179 4.079 4.875
4.20 4.10
4.221 4.121
VBATT 0.3V GND, VBATT
0.75
µF/A
VBATT 0.33µF
0.25
VBATT 5.1V
SOT23, Single-Cell Battery Charger Current-Limited Supply
ELECTRICAL CHARACTERISTICS (continued)
(VIN 10V, VBATT 4.2V MAX1736EUT42 4.1V MAX1736EUT41, +85°C. Typical values +25°C, unless otherwise noted.)
MAX1736
PARAMETER Pullup Current Minimum On-Time Minimum Off-Time Pullup Resistance 0.33µF 0.33µF
CONDITIONS
UNITS
ELECTRICAL CHARACTERISTICS
(VIN 10V, VBATT 4.2V MAX1736EUT42 4.1V MAX1736EUT41, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER Input Voltage (Note Fast-Charge BATT Qualification Threshold BATT Regulation Voltage BATT Removal Detection Threshold BATT Input Current, Input Power Removed BATT Input Current, Charger Disabled BATT Input Current, When Charging Precharge Source Current Input Current GATE Source/Sink Current GATE Drive Source Current Battery Removal Logic High Threshold Logic Threshold Pulldown Current Pullup Current Pullup Resistance VBATT 5.1V VBATT
CONDITIONS External P-MOSFET BATT rising, transition from precharge fast charge MAX1736EUT42 MAX1736EUT41 BATT rising VBATT 0.3V GND, VBATT
4.158 4.058 4.85
2.65 4.242 4.142 5.125 0.75
UNITS
Note devices 100% production tested +25°C. Limits over operating temperature range guaranteed design. Note input voltage range specified with external PFET off. When charging, PFET turns input voltage (the output voltage constant-current power source) drops very near battery voltage. When PFET 2.5V. Note Every (for 0.33µF) MAX1736 turns external P-channel MOSFET samples determine input power present. input power removed, charger shuts down. Note design guidance, tested.
SOT23, Single-Cell Battery Charger Current-Limited Supply MAX1736
Typical Operating Characteristics
+25°C, unless otherwise noted.)
MINIMUM ON/OFF-TIMES
MAX1736 toc01
MAX1736-02
0.20 BATT VOLTAGE DEVIATION 0.15 0.10 0.05 0.00 -0.05 -0.10 -0.15
PRECHARGE CURRENT (mA) PRECHARGE CURRENT (mA)
VBATT
MINIMUM ON/OFF-TIME (ms)
1000
MINIMUM ON-TIME
VBATT VBATT
MINIMUM OFF-TIME
(µF)
-0.20 TEMPERATURE (°C)
INPUT DETECTION INTERVAL
MAX1736 toc04
TYPICAL OPERATING WAVEFORMS
5V/div VBATT 200mV/div AC-COUPLED PFET PFET
MAX1736 toc05
1000 INPUT DETECTION INTERVAL
1A/div VGATE 10V/div
(µF) 10ms/div
MAX1736-03
10,000
BATT REGULATION VOLTAGE DEVIATION TEMPERATURE
PRECHARGE CURRENT INPUT VOLTAGE
SOT23, Single-Cell Battery Charger Current-Limited Supply
Description
NAME GATE DESCRIPTION Input Voltage from Current-Limited Voltage Source (22V max). Bypass with 0.1µF capacitor. charging current current limit external power supply. Gate Drive External PMOS Pass Element. PMOS device should have threshold 2.5V less (see Selecting External Components). Ground. Connect battery's negative terminal GND. Logic-Level Enable Input. Pull disable MAX1736. internally pulled VBATT 100mV through 350k, draws current from BATT. Charge Time Control. Sets minimum on-time, minimum off-time, detection interval. Place 0.33µF capacitor between most applications (see Selecting External Components). Cell Voltage Monitor Input, Precharge Current Output, MAX1736 Power Source. Connect BATT positive terminal single cell. Bypass BATT with capacitor (1.5µF charge current).
MAX1736
BATT
Detailed Description
MAX1736 provides simple, safe, low-cost method charging single-cell battery with nearly heat generation. Combined with current-limited voltage source, MAX1736 provides precharge, fast-charge, top-off-charge capabilities. After constant-current fast charge, top-off safely finishes charging battery pulse-width modulating charge current. top-off on-time kept below electrochemical time constant cell. advantage this method that charge circuit small generates minimal heat while providing safe method charging ensure maximum cell life. Figure shows MAX1736 functional diagram.
specified current limit that matches desired fastcharge current cell. With P-channel MOSFET will nearly equal VBATT. detect that input supply connected, MAX1736 periodically turns P-channel MOSFET checks voltage During fast charge, this occurs once every input detection interval (20s with 0.33µF). During pulsed top-off, input detection occurs more frequently continuous when MOSFET (see Selecting External Components).
Pulsed Top-Off
When battery approaches full charge, instantaneous voltage reaches BATT regulation voltage pulsed top-off begins. MAX1736 uses hysteretic algorithm with minimum off-time. Cell voltage sampled with charging current minimize errors battery cell protection resistance. voltage below BATT regulation voltage, P-channel MOSFET switches minimum on-time. minimum on-time, cell voltage still below BATT regulation voltage, switch remains until cell voltage reaches BATT regulation voltage. that point, P-channel MOSFET then switches least minimum off-time. minimum on-time should below electrochemical time constant cell. value 0.33µF sets minimum on-time 165ms, which adequate most batteries.
Precharge
protect cells from damage that occur fast charged from dead state, MAX1736 precharges cell with start charging cycle when cell voltage below 2.5V. soon cell voltage reaches 2.5V, MAX1736 begins fast charging.
Fast Charge
fast-charge mode, MAX1736 turns external P-channel MOSFET. Charging current current limit external supply; current regulated MAX1736. P-channel MOSFET used only switch, linear regulator. Therefore, circuit's power dissipation minimized, permitting rapid charge cycles with almost heat generation. external power supply should have
SOT23, Single-Cell Battery Charger Current-Limited Supply MAX1736
VBATT 100mV
GATE
350k
10µA 1.4V STATE MACHINE 4.2V (4.1V) BATT
0.4V
MAX1736EUT42 (MAX1736EUT41)
Figure Functional Diagram
Once switch turns off, remains least minimum off-time. After minimum off-time, Pchannel MOSFET turns cell voltage lower than BATT regulation voltage. value 0.33µF sets minimum off-time 33ms. beginning pulsed top-off state, charge current modulated approximately duty cycle. Toward top-off, charge current stays long periods time between single "on" pulses. During these final pulses, instantaneous cell voltage exceed BATT regulation voltage several hundred millivolts, these pulses orders magnitude shorter than electrochemical time constant cell harm. Pulsed top-off charge ends when cell voltage longer falls below BATT regulation voltage. Figure shows state machine.
external power source, MAX1736. Pchannel MOSFET Figure application circuit either off, allowing source directly connected cell disconnected. Therefore, important choose power supply with correct current limit cell charged. most applications, this will small wall cube with open-circuit output voltage 12V, which specified "current limited" "constant current." Some low-cost wall cubes have poor transient characteristics. these wall cubes, output current exceed specified current limit several times when load quickly connected. MAX1736 limits this current peak controlling slew rate P-channel MOSFET. GATE more information.
Selecting External Components
Input Power Supply
reason MAX1736 charger compact simple that charging current
PMOS Switch
P-channel MOSFET switches current-limited source off. Because intentionally slow switching times limited slew rate, MAX1736 particular about power drives. Specifications consider when choosing appropriate
SOT23, Single-Cell Battery Charger Current-Limited Supply MAX1736
CHARGER POWER REMOVED (FROM STATE) CHARGER POWER PRESENT SHUTDOWN FET: DISABLED FET: PRECHARGE FET: IOUT -6mA (FROM STATE)
VBATT 2.5V
EVERY CYCLE
CHARGER POWER PRESENT
DETECTION INTERVAL
CHARGER POWER PRESENT
TOP-OFF FET: PULSED
VBATT 4.2V
FAST-CHARGE FET:
Figure State Machine
minimum drain-source breakdown voltage minimum turn-on threshold voltage Power dissipation during fast charge approximately RDSON ICHG2, where ICHG current limit input power source. minimum breakdown voltage (BVDS) must typically times wall cube's open-circuit voltage. even larger margin necessary wall adapter especially poor transient response. MAX1736 operate with input voltages 22V.
0.47µF total capacitance should low-ESR ceramic.
VBATT 2.5V
TOP-OFF QUAL FET:
FAST-CHARGE QUAL FET:
VBATT 2.5V
CGATE
Most applications will circuit Figure with CGATE 0.22µF, RGATE 100k, 0.33µF. CGATE, RGATE, internal 100µA pull-up pulldown current sources slow switching Pchannel MOSFET. This prevents wall cube with poor transient response from subjecting excessive voltage when P-channel MOSFET turns off, prevents excessive current into battery when Pchannel MOSFET turns Excessive voltage potentially damage input capacitor, PMOS switch. Excessive current into battery cause errors termination process MAX1736 raising instantaneous battery voltage) trip battery's protection circuitry. applications utilizing wall cube with poor transient response, increase value CGATE needed
BATT Capacitor
Bypass BATT with least 1.5µF charge current. battery removed while P-channel MOSFET BATT voltage over quickly sensed, immediately turned off. applications where cell removable, very large capacitance values increase transient currents when cell replaced. Therefore, BATT capacitance excess 100µF should avoided. best system performance with large output capacitance, least
SOT23, Single-Cell Battery Charger Current-Limited Supply MAX1736
further slow switching edges prevent transient spikes. sets minimum on-time off-time according following equations: tON(MIN) tOFF(MIN)
GATE CURRENT-LIMITED WALL CUBE (800mA)
FDC638P PFET 0.22µF
100k
Layout Guidelines
MAX1736 controls GATE slew rate; consequently, board layout sensitive noise high-frequency switching regulator. addition, since cell voltage sensed both during between highcurrent pulses, system insensitive ground errors. However, Maxim recommends maintaining large ground area large traces high-current paths. Refer MAX1736EVKIT recommended layout example.
0.1µF
BATT 2.2µF MAX1736
SINGLE CELL
0.33µF
Figure Simple Application Circuit
Chip Information
TRANSISTOR COUNT: 1622
Package Information
6LSOT.EPS
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2000 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

SOT23, Single-Cell Battery Charger Current-Limited Supply Small 6

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