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19-2902; Rev 0; 7/03
SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers
General Description
The MAX1551/MAX1555 charge a single-cell lithium-ion (Li+) battery from both USB* and AC adapter sources. They operate with no external FETs or diodes, and accept operating input voltages up to 7V. On-chip thermal limiting simplifies PC board layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1551/MAX1555 thermal limits are reached, the chargers do not shut down, but progressively reduce charging current. The MAX1551 includes a POK output to indicate when input power is present. If either charging source is active, POK goes low. The MAX1555 instead features a CHG output to indicate charging status. With USB connected, but without DC power, charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs with no port communication required. When DC power is connected, charging current is set at 280mA (typ). No input-blocking diodes are required to prevent battery drain. The MAX1551/MAX1555 are available in 5-pin thin SOT23 packages and operate over a -40C to +85C range. o Charge from USB or AC Adapter o Automatic Switchover when AC Adapter is Plugged In o On-Chip Thermal Limiting Simplifies Board Design o Charge Status Indicator o 5-Pin Thin SOT23 Package o Protected by U.S. Patent #6,507,172
Features
MAX1551/MAX1555
Ordering Information
PART MAX1551EZK-T MAX1555EZK-T TEMP RANGE -40C to +85C -40C to +85C PIN-PACKAGE 5 Thin SOT23-5 5 Thin SOT23-5
Selector Guide
PART MAX1551EZK MAX1555EZK TOP MARK ADRT ADRU FEATURES POK Output CHG Output
Applications
PDAs Wireless Appliances Cell Phones Digital Cameras
Pin Configuration
TOP VIEW
USB 1 5 BAT
AC ADAPTER 3.7V TO 7V DC
Typical Operating Circuit
BAT TO SYSTEM LOAD Li+
GND 2
MAX1551 (MAX1555)
4 DC
USB 3.7V TO 6V
USB
CHARGE CONTROL TO LOGIC RAIL
POK 3 (CHG)
LOGIC CONTROL
POK (CHG)
THIN SOT23
MAX1551 (MAX1555)
GND
*Protected by U.S. Patent #6,507,172. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers MAX1551/MAX1555
ABSOLUTE MAXIMUM RATINGS
DC to GND......................................................................0 to +8V DC to BAT .......................................................................0 to +7V BAT, CHG, POK, USB to GND .................................-0.3V to +7V Continuous Power Dissipation (TA = +70C) 5-Pin Thin SOT23 (derate 9.1mW/C above +70C) ....727mW Operating Temperature Range ...........................-40C to +85C Junction Temperature Range ............................-40C to +150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDC = 5V, VUSB = 0, IBAT = 0, CBAT = 1F, TA = 0C to +85C, unless otherwise noted.)
PARAMETER DC DC Voltage Range DC to BAT Voltage Range DC Undervoltage Lockout Threshold DC Supply Current DC to BAT On-Resistance DC to BAT Dropout Voltage USB USB Voltage Range USB Undervoltage Threshold USB Supply Current USB to BAT On-Resistance USB to BAT Dropout Voltage BAT BAT Regulation Voltage DC Charging Current USB Charging Current BAT Prequal Threshold Prequalification Charging Current BAT Leakage Current POK, CHG, AND THERMAL LIMIT CHG Threshold CHG, POK Logic-Low Output CHG, POK Leakage Current Thermal-Limit Temperature Charge current where CHG goes high, IBAT falling, 50mA hysteresis ICHG, IPOK = 10mA VCHG, VPOK = 6V, TA = +25C Charge current reduced by 17mA/C above this temperature 25 50 150 0.001 +110 100 300 1 mA mV A C VDC or VUSB = 5V VBAT = 3.3V, VUSB = 0, VDC = 5V VBAT = 3.3V, VDC = 0, VUSB = 5V VBAT rising, 100mV hysteresis VBAT = 2.8V VDC = VUSB = 0, VBAT = 4.2V 4.158 220 80 2.9 20 4.2 280 90 3 40 4.242 340 100 3.1 80 5 V mA mA V mA A (Note 1) Input rising, 430mV hysteresis, VDC = 0, VBAT = 3V (Note 1) VUSB = 5V, VDC = 0 VUSB = 3.7V, VBAT = 3.6V, VDC = 0 When charging stops, VBAT = 4V, USB falling, 200mV hysteresis, VDC = 0 3.7 3.75 3.95 1.65 2 30 60 6.0 4.15 3 4 90 V V mA mV VDC = 3.7V, VBAT = 3.6V When charging stops, VBAT = 4V, DC falling, 200mV hysteresis 30 Input rising, 430mV hysteresis, VBAT = 3V (Note 1) (Note 1) 3.7 0.1 3.75 3.95 1.75 1 60 7.0 6.0 4.15 3 2 90 V V V mA mV CONDITIONS MIN TYP MAX UNITS
2
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SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers
ELECTRICAL CHARACTERISTICS
(VDC = 5V, VUSB = 0, IBAT = 0, CBAT = 1F, TA = -40C to +85C, unless otherwise noted.) (Note 2)
PARAMETER DC DC Voltage Range DC to BAT Voltage Range DC Undervoltage Lockout Threshold DC Supply Current DC to BAT On-Resistance DC to BAT Dropout Voltage USB USB Voltage Range USB Undervoltage Lockout Threshold USB Supply Current USB to BAT On-Resistance USB to BAT Dropout Voltage BAT BAT Regulation Voltage DC Charging Current USB Charging Current BAT Prequal Threshold Prequalification Charging Current BAT Leakage Current POK, CHG CHG Threshold CHG, POK Logic-Low Output CHG, POK Leakage Current Charge current where CHG goes high, IBAT falling, 50mA hysteresis ICHG, IPOK = 10mA VCHG, VPOK = 6V, TA = +25C 25 100 300 1 mA mV A VDC or VUSB = 5V VBAT = 3.3V, VUSB = 0, VDC = 5V VBAT = 3.3V, VDC = 0, VUSB = 5V VBAT rising, 100mV hysteresis VBAT = 2.8V VDC = VUSB = 0, VBAT = 4.2V 4.141 220 80 2.9 20 4.259 340 100 3.1 80 5 V mA mA V mA A (Note 1) Input rising, 430mV hysteresis, VDC = 0, VBAT = 3V (Note 1) VUSB = 5V, VDC = 0 VUSB = 3.7V, VBAT = 3.6V, VDC = 0 When charging stops, VBAT = 4V, USB falling, 200mV hysteresis, VDC = 0 30 3.7 3.75 6.0 4.15 3 4 95 V V mA mV VDC = 3.7V, VBAT = 3.6V When charging stops, VBAT = 4V, DC falling, 200mV hysteresis 30 Input rising, 430mV hysteresis, VBAT = 3V (Note 1) (Note 1) 3.7 0.1 3.75 7.0 6.0 4.15 3 2 95 V V V mA mV CONDITIONS MIN MAX UNITS
MAX1551/MAX1555
Note 1: The input undervoltage lockout has 430mV of hysteresis. The charger turns on when an input rises to 3.95V (typ), and turns off when it falls below 3.52V. Note 2: Specifications to -40C are guaranteed by design, not production tested.
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3
SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers MAX1551/MAX1555
Typical Operating Characteristics
(VDC = 5V, VUSB = 0, IBAT = 0, CBAT = 1F, TA = +25C, unless otherwise noted.)
CHARGE CURRENT vs. DC VOLTAGE HEADROOM
MAX1551/55 toc01
CHARGE CURRENT vs. USB VOLTAGE HEADROOM
MAX1551/55 toc02
DC CHARGE CURRENT vs. BATTERY VOLTAGE
MAX1551/55 toc03
300 250 CHARGE CURRENT (mA) 200 150 100 50 0 VBAT = 3.8V, VDC FALLING -50 0 0.1 0.2 0.3 0.4
100 80 CHARGE CURRENT (mA) 60 40 20 0 VDC = 0, VBAT = 3.8V, VUSB FALLING -20
300 250 DC CHARGE CURRENT (mA) 200 150 100 50 0 -50
0.5
0
0.1
0.2
0.3
0.4
0.5
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 BATTERY VOLTAGE (V)
DC VOLTAGE HEADROOM (VDC - VBAT) (V)
USB VOLTAGE HEADROOM (VUSB - VBAT) (V)
USB CHARGE CURRENT vs. BATTERY VOLTAGE
MAX1551/55 toc04
DC CHARGE CURRENT vs. AMBIENT TEMPERATURE
MAX1551/55 toc05
BATTERY TERMINATION VOLTAGE vs. TEMPERATURE
BAT OPEN BATTERY TERMINATION VOLTAGE (V) 4.21
MAx1551/55 toc06
100 80 60 40 20 0 -20 0
300 250 DC CHARGE CURRENT (mA) THERMAL LIMIT ACTIVATED 200 150 100 50 0 VBAT = 3.8V, VDC = 5V -50
4.22
USB CHARGE CURRENT (mA)
4.20
4.19
4.18 25 35 45 55 65 75 85 -40 -15 10 35 60 85 TEMPERATURE (C) TEMPERATURE (C)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 BATTERY VOLTAGE (V)
OFF-BATTERY LEAKAGE CURRENT vs. DC INPUT VOLTAGE
OFF-BATTERY LEAKAGE CURRENT (A) VDC = 0, SWEEPING USB 0 TO 5V OR VUSB = 0, SWEEPING DC 0 TO 5V VBAT = 4.2V 1.5 0V 1.0 0V
MAX1551/55 toc07
USB-TO-DC TRANSITION WAVEFORM
MAX1551/55 toc08
2.5
2.0
BATTERY CURRENT 200mA/div 0A VUSB 5V/div
0.5
VPOK 2V/div VDC 5V/div 400ms/div
0 0 1 2 3 4 5 DC OR USB INPUT VOLTAGE (V)
0V
4
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SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers
Pin Description
PIN 1 2 NAME USB GND POK 3 CHG FUNCTION USB Port Charger Supply Input. USB draws up to 100mA to charge the battery. Decouple USB with a 1F ceramic capacitor to GND. Ground Power-OK Active-Low Open-Drain Charger Status Indicator. POK pulls low when either charger source is present (MAX1551 only). Active-Low Open-Drain Charge Status Indicator. CHG pulls low when the battery is charging. CHG goes to a high-impedance state, indicating the battery is fully charged, when the charger is in voltage mode and charge current falls below 50mA. CHG is high impedance when both input sources are low (MAX1555 only). DC Charger Supply Input for an AC Adapter. DC draws 280mA to charge the battery. Decouple DC with a 1F ceramic capacitor to GND. Battery Connection. Decouple BAT with a 1F ceramic capacitor to GND.
MAX1551/MAX1555
4 5
DC BAT
Detailed Description
The MAX1551/MAX1555 charge a single-cell Li+ battery from both USB and AC adapter sources, enabling portable users to forgo carrying a wall cube. These devices operate with no external FETs or diodes, and accept operating input voltages up to 7V. An internal thermal control loop simplifies PC board layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1551/MAX1555 thermal limits are reached, the chargers do not shut down, but simply reduce charging current by 17mA/C above a die temperature of +110C. With USB connected, but without DC power, the charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs with no port communication required. When DC power is connected, charging current is set at 280mA (typ). The MAX1551/MAX1555 do not feature an enable input. Once power is connected to USB and/or DC, the charger is on. When input power is removed, battery leakage current is less than 5A. No input-blocking diodes are required to prevent battery drain. Insert a diode at DC (the adapter input) if protection from negative voltage inputs (reversed-polarity adapter plugs) is required.
USB to Adapter Power Handoff
The MAX1551/MAX1555 can charge from either the USB input or the DC input. The battery does not charge from both sources at the same time. The MAX1551/ MAX1555 automatically detect the active input and charge from that. If both power sources are active, the DC input takes precedence. The switchover between DC and USB is detailed in Table 1.
MAX1551 Power-OK (POK)
The MAX1551's POK is an active-low, open-drain output that goes low when VDC or VUSB is above 3.95V. POK can be used as a logic output or can drive an LED. POK indicates the charger is connected to input power and is charging.
MAX1555 Charge Status (CHG)
The MAX1555's CHG is an active-low, open-drain charge status indicator. CHG pulls low when the battery is charging (whenever USB or DC are powered) and charge current is greater than 50mA. CHG indicates when the battery is fully charged by going high impedance when the charger is in voltage mode and charge current falls below 50mA. Charging does not stop when CHG goes high. CHG is low in precharge mode.
Table 1. USB and DC Input Selection
VDC > 7V OR VUSB > 6V Exceeds operating input range. Not allowed. See the Absolute Maximum Ratings section. VDC > 3.95V AND VUSB DON'T CARE 280mA (typ) charging from DC VDC < 3.52V AND 3.95V < VUSB < 6V 100mA (max) charging from USB VDC AND VUSB < 3.52V Undervoltage lockout
(VDC takes precedence when both inputs are present.) _______________________________________________________________________________________ 5
SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers MAX1551/MAX1555
Precharge Current
The MAX1551/MAX1555 feature a precharge current to protect deeply discharged cells. If VBAT is less than 3V, the device enters precharge mode where charging current is limited to 40mA. not shut down, but progressively reduce charging current by 17mA/C above a die temperature of +110C. Solder the MAX1551/MAX1555s' GND to a large ground plane to help dissipate power and keep the die temperature below the thermal limit. The USB charge current of 100mA is unlikely to induce thermal limiting.
Package Thermal Limiting
On-chip thermal limiting in the MAX1551/MAX1555 simplifies PC board layout and allows charging rates to be optimized without the limits imposed by worst-case battery and input voltages. The device reduces the power dissipation at BAT to prevent overheating. This allows the board design to be optimized for compact size and typical thermal conditions. When the MAX1551/ MAX1555 thermal limits are reached, the chargers do
Bypass Capacitors
Use ceramic bypass capacitors at DC, USB, and BAT. Mount these capacitors within 1cm of their respective pins. X7R and X5R dielectrics are recommended.
Chip Information
TRANSISTOR COUNT: 541 PROCESS: BiCMOS
Typical Application Circuit
AC ADAPTER 3.7V TO 7V C1 1F DC BAT Li+ C3 1F TO SYSTEM LOAD
USB 3.7V TO 6V C2 1F
USB
CHARGE CONTROL
TO LOGIC RAIL R1 100k INDICATES THAT POWER IS PRESENT (EITHER DC OR USB)
LOGIC CONTROL
POK (CHG)
MAX1551 (MAX1555)
GND
6
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SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
MAX1551/MAX1555
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7
SOT23 Dual-Input USB/AC Adapter 1-Cell Li+ Battery Chargers MAX1551/MAX1555
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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