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19-2890; Rev 0; 6/03
KIT ATION EVALU E AILABL AV
Linear Li+ Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN
General Description
The MAX1508 is an intelligent, stand-alone constant-current, constant-voltage (CCCV), thermally regulated linear charger for a single-cell lithium-ion (Li+) battery. The MAX1508 integrates the current-sense circuit, MOS pass element, and thermal-regulation circuitry, and also eliminates the reverse-blocking Schottky diode, to create the simplest and smallest charging solution for hand-held equipment. The MAX1508 functions as a stand-alone charger to control the charging sequence from the prequalification state through fast-charge, top-off charge, and fullcharge indication. Proprietary thermal-regulation circuitry limits the die temperature to +100C when fast charging or while exposed to high ambient temperatures, allowing maximum charging current without damaging the IC. The MAX1508 achieves high flexibility by providing an adjustable fast-charge current by an external resistor. Other features include the charging status (CHG) of the battery, an active-low control input (EN), and an activelow-input power-source detection output (ACOK). The MAX1508 accepts a +4.25V to +13V supply, but disables charging when the input voltage exceeds +7V to protect against unqualified or faulty AC adapters. The MAX1508 operates over the extended temperature range (-40C to +85C) and is available in a compact 8-pin thermally enhanced 3mm x 3mm thin DFN package with 0.8mm height.
Features
o Stand-Alone Linear 1-Cell Li+ Battery Charger o No External FET, Reverse-Blocking Diode, or Current-Sense Resistor Required o Programmable Fast-Charge Current (0.8A max) o Proprietary Die-Temperature Regulation Control (+100C) o +4.25V to +13V Input Voltage Range with Input Overvoltage Protection (OVP) Above +7V o Charge-Current Monitor for Fuel Gauging o Low Dropout Voltage--130mV at 0.425A o Input Power-Source Detection Output (ACOK) and Charge-Enable Input (EN) o Soft-Start Limits Inrush Current o Charge Status Output (CHG) for LED or Microprocessor Interface o Small 3mm x 3mm 8-Pin Thin DFN Package, 0.8mm High
MAX1508
Ordering Information
PART MAX1508ETA TEMP RANGE -40C to +85C PIN-PACKAGE 8 Thin DFN-EP* TOP MARK AHF
Applications
Cellular and Cordless Phones PDAs Digital Cameras and MP3 Players USB Appliances Charging Cradles and Docks BluetoothTM Equipment
*EP = Exposed paddle.
Typical Operating Circuit
INPUT 4.25V TO 13V IN 1F
BATT
Pin Configuration
CHG BATT EN
TOP VIEW
ACOK
1F
Li+ 4.2V
8
7
6
5
MAX1508
CHG OFF
ISET
MAX1508
EN ON VL 0.47F
ACOK
GND
2.80k
1 VL
2 IN
3 GND
4 ISET
3mm x 3mm THIN DFN
Bluetooth is a trademark of Ericsson. ________________________________________________________________ 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.
Linear Li+ Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
ABSOLUTE MAXIMUM RATINGS
IN, CHG to GND .....................................................-0.3V to +14V VL, BATT, ISET, EN, ACOK to GND .........................-0.3V to +6V VL to IN...................................................................-14V to +0.3V IN to BATT Continuous Current.............................................0.9A Continuous Power Dissipation (TA = +70C) 8-Pin TDFN (derate 24.4mW/C above +70C) .........1951mW Short-Circuit Duration.................................................Continuous Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+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
(VIN = 5V, VBATT = 4.0V, ACOK = EN = CHG = unconnected, RISET = 2.8k to GND, CVL = 0.47F, BATT bypassed to GND with 1F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Input Voltage Range Input Operating Range ACOK Trip Point, IN Overvoltage Lockout Trip Point VIN - VBATT, VIN rising VIN - VBATT, VIN falling VIN rising VIN hysteresis Charging (IIN - IBATT) IN Input Current VL Output Voltage VL Load Regulation VL Temperature Coefficient VL Undervoltage Lockout Trip Point BATT Input Current Maximum RMS Charge Current Battery Regulation Voltage BATT Removal Detection Threshold IBATT = 0 VBATT rising TA = 0C to +85C TA = -40C to +85C 4.162 4.150 4.4 Disabled, EN = VL OFF state (VIN = VBATT = 4.0V) IVL = 100A IVL = 100A to 2mA IVL = 100A VIN rising Hysteresis VIN = 0 to 4V EN = VL 3.3 -71 -2 2.95 0.17 3 4 0.8 4.2 4.2 4.67 4.238 4.250 4.9 10 10 -200 CONDITIONS MIN 0 4.25 20 15 6.5 40 30 7 0.11 1 0.8 2 1.5 0.065 V mV mV/C V A A V V mA TYP MAX 13 6.50 60 45 7.5 UNITS V V mV V
2
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Li+ Linear Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V, VBATT = 4.0V, ACOK = EN = CHG = unconnected, RISET = 2.8k to GND, CVL = 0.47F, BATT bypassed to GND with 1F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER BATT Removal Detection-Threshold Hysteresis Minimum BATT Bypass Capacitance Fast-Charge Current-Loop System Accuracy Precharge Current System Accuracy Die-Temperature-Regulation Set Point VBATT Precharge Threshold Voltage Current-Sense Amplifier Gain, ISET to IBATT in Fast-Charge Mode Regulator Dropout Voltage (VIN - VBATT ) EN Logic Input Low Voltage EN Logic Input High Voltage EN Internal Pulldown Resistor CHG Output Low Current CHG Output High Leakage Current ACOK Output Low Voltage ACOK Output High Leakage Current Full-Battery Detection Current Threshold (as a Percentage of the Fast-Charge Current) V CHG = 1V V CHG = 13V IACOK = 0.5mA V ACOK = 5.5V IBATT falling TA = +25C TA = +85C 5 0.002 10 15 TA = +25C TA = +85C 0.002 0.4 1 VBATT rising IBATT = 500mA, VISET = 1.4V VBATT = 4.1V, IBATT = 425mA 4.25V < VIN < 6.5V 4.25V < VIN < 6.5V 1.3 100 5 200 12 400 20 1 2.3 0.880 VBATT = 3.5V Percentage of the fast-charge current, VBATT = 2.2V 478 5 CONDITIONS MIN TYP 200 1 520 10 100 2.5 0.958 130 2.7 1.035 200 0.52 562 15 MAX UNITS mV F/A mA % C V mA/A mV V V k mA A V A %
MAX1508
Note 1: Limits are 100% production tested at TA = +25C. Limits over operating temperature range are guaranteed through correlation using statistical quality control (SQC) methods.
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3
Linear Li+ Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
Typical Operating Characteristics
(VIN = 5V, VBATT = 4.0V, ACOK = EN = CHG = unconnected, RISET = 2.8k to GND, CIN = 1F, CBATT = 1F, CVL = 0.47F, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1508 toc01
DISABLED-MODE SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1508 toc02
CHARGE CURRENT vs. BATTERY VOLTAGE
550 500 CHARGE CURRENT (mA) 450 400 350 300 250 200 150 100
MAX1508 toc03
2.0 IBATT = 0 1.5
2.0 DISABLED-MODE SUPPLY CURRENT (mA) EN = VL 1.5
600
SUPPLY CURRENT (mA)
1.0
1.0
0.5
0.5
0 0 2 4 6 8 10 12 INPUT VOLTAGE (V)
0 0 2 4 6 8 10 12 INPUT VOLTAGE (V)
0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 BATTERY VOLTAGE (V)
CHARGE CURRENT vs. INPUT VOLTAGE
600 550 500 450 400 350 300 250 200 150 100 50 0 INPUT VOLTAGE (V) 600 550 500 450 400 350 300 250 200 150 100 50 0
MAX1508 toc04
CHARGE CURRENT vs. INPUT-VOLTAGE HEADROOM
MAX1508 toc05
BATTERY REGULATION VOLTAGE vs. TEMPERATURE
4.207 4.204 4.201 4.198 4.195 4.192 4.189 4.186 4.183 4.180
MAX1508 toc06
4.210 BATTERY REGULATION VOLTAGE (V)
CHARGE CURRENT (mA)
0 1 2 3 4 5 6 7 8 9 10 11 12 13
CHARGE CURRENT (mA)
0 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 VIN - VBATT (V)
-40
-15
10
35
60
85
TEMPERATURE (C)
CHARGE CURRENT vs. AMBIENT TEMPERATURE
MAX1508 toc07
CHARGE CURRENT vs. AMBIENT TEMPERATURE
900 800 CHARGE CURRENT (mA) 700 600 500 400 300 200 100 0 RISET = 1.87k -40 -15 10 35 60 85 VBATT = 3.6V VBATT = 4.0V
MAX1508 toc09
600 580 CHARGE CURRENT (mA) 560 540 520 500 480 460 440 420 -40 -15 10 35 60
1000
85
AMBIENT TEMPERATURE (C)
AMBIENT TEMPERATURE (C)
4
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Li+ Linear Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN
Pin Description
PIN 1 2 3 4 NAME VL IN GND ISET FUNCTION Internally Generated Logic Supply for Chip. Bypass VL to GND with a 0.47F capacitor. Input Supply Voltage. Bypass IN to GND with a 1F capacitor to improve line noise and transient rejection. Ground. Connect GND and exposed pad to a large copper trace for maximum power dissipation. Charge-Current Program and Fast-Charge Current Monitor. Output current from ISET is 0.958mA per amp of battery charging current. The charging current is set by connecting a resistor from ISET to GND. Fast-charge current = 1461V / RISET. Logic-Level Enable Input. Drive EN high to disable charger. Pull EN low or float for normal operation. EN has an internal 200k pulldown resistor. Input Power-Detection Output. The open-drain ACOK output asserts low when +4.25V < VIN < +7V and VIN VBATT > 40mV. ACOK requires an external 100k pullup resistor. ACOK is high impedance in shutdown. Li+ Battery Connection. Bypass BATT to GND with a capacitor of at least 1F per ampere of charge current. Charging Indicator, Open-Drain Output. CHG goes low (and can turn on an LED) when charging begins. CHG is high impedance when the battery current drops below 10% of the fast-charging current, or when EN is high. Connect a pullup resistor to the P's I/O voltage when interfacing with a P logic input. Exposed Pad. Connect exposed pad to a large copper trace for maximum power dissipation. The pad is internally connected to GND.
MAX1508
5 6 7 8
EN ACOK BATT CHG
--
PAD
Detailed Description
The MAX1508 charger uses voltage, current, and thermal-control loops to charge a single Li+ cell and to protect the battery (Figure 1). When a Li+ battery with a cell voltage below 2.5V is inserted, the MAX1508 charger enters the prequalification stage where it precharges that cell with 10% of the user-programmed fast-charge current. The CHG indicator output is driven low (Figure 2) to indicate entry into the prequalification state. Once the cell has passed 2.5V, the charger soft-starts before it enters the fast-charge stage. The fast-charge current level is programmed through a resistor from ISET to ground. As the battery voltage approaches 4.2V, the charging current is reduced. If the battery current drops to less than 10% of the fast-charging current, the CHG indicator goes high impedance, signaling the battery is fully charged. At this point the MAX1508 enters a constant voltage-regulation mode to maintain the battery at full charge. If, at any point while charging the battery, the die temperature approaches +100C, the MAX1508 reduces the charging current so the die temperature does not exceed the temperature-regulation set point.
The thermal-regulation loop limits the MAX1508 die temperature to +100C by reducing the charge current as necessary (see the Thermal Regulation section). This feature not only protects the MAX1508 from overheating, but also allows higher charge current without risking damage to the system.
EN Charger Enable Input
EN is a logic input (active low) to enable the charger. Drive EN low, leave floating, or connect to GND to enable the charger control circuitry. Drive EN high to disable the charger control circuitry. EN has a 200k internal pulldown resistance.
ACOK Output
Active-Low Output. The open-drain ACOK output asserts low when +4.25V < VIN < +7V and VIN - VBATT > 40mV. ACOK requires an external 100k pullup resistor to the system's logic I/O voltage. ACOK is high impedance in shutdown.
VL Internal Voltage Regulator
The MAX1508 linear charger contains an internal linear regulator available on the VL output pin. VL requires a 0.47F ceramic bypass capacitor to GND. VL is regulated to 3.3V whenever the input voltage is above 3.5V.
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5
Linear Li+ Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
CHG Charge Indicator Output
CHG is an open-drain current source for indicating charge status. Table 1 describes the state of CHG during different stages of operation. CHG is a nominal 12mA current source suitable for driving a charge-indication LED. If the MAX1508 is used in conjunction with a microprocessor, a pullup resistor to the logic I/O voltage allows CHG to indicate charge status to the P instead of driving an LED.
Soft-Start
An analog soft-start algorithm activates when entering fast-charge mode. When the prequalification state is complete (VBATT exceeds +2.5V), the charging current ramps up in 3ms to the full charging current. This reduces the inrush current on the input supply.
MAX1508
IN BATT
OUTPUT DRIVER, CURRENT SENSE, AND LOGIC
VREF
ISET
TEMPERATURE SENSOR
IREF
100C
IN VL 0.47F VLUVLO REF IN VINOVLO INOK VLOK ON VL
IN VI/O
BATT ACOK
N
LOGIC CHG N REFOK REFOK EN
200k
GND
Figure 1. Functional Diagram 6 _______________________________________________________________________________________
Li+ Linear Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
ASYNCHRONOUS FROM ANYWHERE VIN > 7V + VBATT > VIN + EN = HIGH SHUTDOWN VBATT < 2.5V
ND V A ND < 7 ATT A V IN > V B V IN = LOW EN
CHARGER = OFF LED = OFF
PRECHARGE
100% CHARGE CURRENT LED = ON
VIN > 7V + VBATT > VIN + EN = HIGH
VBATT < 2.4V VBATT > 2.5V
FAST CHARGE
100% CHARGER CURRENT LED = ON
ICHARGE > 20% OF ISET
ICHARGE < 10% OF ISET
FULL BATT
LED = OFF
FULL BATT CONTINUES TO REGULATE BATT UP TO 4.2V
Figure 2. Charge State Diagram
Applications Information
Charge-Current Selection
The maximum charging current is programmed by an external RISET resistor connected from ISET to GND. Select the RISET value based on the following formula: IFAST = 1461V / RISET where IFAST is in amps and RISET is in ohms. ISET can also be used to monitor the fast-charge current level. The output current from the ISET pin is 0.958mA per amp of charging current. The output voltage at ISET is proportional to the charging current as follows: VISET = (ICHG x RISET) / 1044
The voltage at ISET is nominally 1.4V at the selected fast-charge current, and falls with charging current as the cell becomes fully charged.
Thermal Regulation
The MAX1508 features a proprietary thermal-regulation circuit to protect both the IC and the system from excessive heat. When the MAX1508's die temperature reaches +100C, the charge current is reduced to prevent any additional increase in the die temperature. An active thermal loop does not indicate a fault condition. Thermal regulation allows the MAX1508 to provide continuous charge to the battery under adverse conditions without causing excessive power dissipation.
7
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Linear Li+ Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
Capacitor Selection
Connect a ceramic capacitor from BATT to GND for proper stability. Use a 1F X5R ceramic capacitor for most applications. Connect a 1F ceramic capacitor from IN to GND. Use a larger input bypass capacitor for high input voltages or high charging currents to reduce supply noise. Connect a 0.47F ceramic capacitor from VL to GND. Microprocessor-Interfaced Charger Figure 3 shows the MAX1508 as a P-cooperated Li+ battery charger. The MAX1508 starts charging the battery when EN is low. The P can drive EN high to disable the charger. The MAX1508's ACOK output indicates the presence of a valid AC adapter to the P. CHG can be used to detect the charge status of a battery. By monitoring VISET, the system can measure the charge current. USB-Powered Li+ Charger The universal serial bus (USB) provides a high-speed serial communication port as well as power for the remote device. The MAX1508 can be configured to charge its battery at the highest current possible from the host port. Figure 4 shows the MAX1508 as a USB battery charger. To make the circuit compatible with either 100mA or 500mA USB ports, the circuit initializes at 95mA charging current. The microprocessor then interrogates the host to determine its current capability. If the host port is capable, the charging current is increased to 435mA. The 435mA current was chosen to avoid exceeding the 500mA USB specification.
Thermal Considerations
The MAX1508 is in a thermally enhanced thin DFN package with exposed paddle. Connect the exposed paddle of the MAX1508 to a large copper ground plane to provide a thermal contact between the device and the circuit board. The exposed paddle transfers heat away from the device, allowing the MAX1508 to charge the battery with maximum current, while minimizing the increase in die temperature.
DC Input Sources
The MAX1508 operates from well-regulated DC sources. The full-charging input voltage range is 4.25V to 7V. The device can stand up to 13V on the input without damage to the IC. If VIN is greater than 7V, then the MAX1508 stops charging. An appropriate power supply must provide at least 4.25V when sourcing the desired peak charging current. It also must stay below 6.5V when unloaded.
Layout and Bypassing
Connect a 1F ceramic input capacitor as close to the device as possible. Provide a large copper GND plane to allow the exposed paddle to sink heat away from the device. Connect the battery to BATT as close to the device as possible to provide accurate battery voltage sensing. Make all high-current traces short and wide to minimize voltage drops. For an example layout, refer to the MAX1507/MAX1508 evaluation kit layout.
Application Circuits
Stand-Alone Li+ Charger The MAX1508 provides a complete Li+ charging solution. The Typical Operating Circuit on the front page shows the MAX1508 as a stand-alone Li+ battery charger. The 2.8k resistor connected to ISET sets a charging current of 520mA. The LED indicates when either fast-charge or precharge qualification has begun. When the battery is full, the LED turns off.
Chip Information
TRANSISTOR COUNT: 1812 PROCESS: BiCMOS
Table 1. CHG States
EN X Low Low Low Low High VIN VBATT 4.25V VIN 7V 4.25V VIN 7V 4.25V VIN 7V >7V X VBATT VIN < 2.5V 2.5V 4.2V X X IBATT 0 10% of IFAST IFAST* 10% of IFAST 0 0 CHG Hi-Z Low Low Hi-Z Hi-Z Hi-Z Shutdown Prequalification Fast Charge Full Charge Overvoltage Disabled STATE
X = Don't care. *IFAST is reduced as necessary to maintain the die temperature at +100C. 8 _______________________________________________________________________________________
Li+ Linear Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
4.2V Li+ AC/DC ADAPTER IN 1F
BATT
1F
MAX1508
CHG
GND
VI/O
SYSTEM VL 0.47F ACOK
ISET 2.8k
EN
CHARGE-CURRENT MONITOR VI/O
LOW: CHARGE, HIGH: FULL OR OFF
Figure 3. P-Interfaced Li+ Battery Charger
4.2V Li+ VBUS GND 1F IN
BATT
1F
MAX1508
CHG
GND
VI/O
SYSTEM VL ACOK
USB PORT
0.47F
ISET
EN
15.4k 4.3k
N HIGH: 435mA, LOW: 95mA VI/O
D+ D-
Figure 4. USB Battery Charger _______________________________________________________________________________________ 9
Linear Li+ Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN MAX1508
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.) 6, 8, &10L, QFN THIN.EPS
1 2
L D A A2
PIN 1 ID
D2
1
N
1
b
PIN 1 INDEX AREA
C0.35 [(N/2)-1] x e REF. e
E
DETAIL A
E2
A1
k
C L
C L
L e A e
L
SEMICONDUCTOR
PROPRIETARY INFORMATION TITLE:
DALLAS
PACKAGE OUTLINE, 6, 8 & 10L, TDFN, EXPOSED PAD, 3x3x0.80 mm
NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY
APPROVAL DOCUMENT CONTROL NO. REV.
21-0137
D
10
______________________________________________________________________________________
Li+ Linear Battery Charger with Integrated Pass FET, Thermal Regulation, and ACOK in 3mm x 3mm TDFN
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.)
MAX1508
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40
0.25 MIN. 0.20 REF.
PACKAGE VARIATIONS PKG. CODE T633-1 T833-1 T1033-1 N 6 8 10 D2 1.50-0.10 1.50-0.10 1.50-0.10 E2 2.30-0.10 2.30-0.10 2.30-0.10 e 0.95 BSC 0.65 BSC 0.50 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEC MO229 / WEED-3 b 0.40-0.05 0.30-0.05 0.25-0.05 [(N/2)-1] x e 1.90 REF 1.95 REF 2.00 REF
SEMICONDUCTOR
PROPRIETARY INFORMATION TITLE:
DALLAS
PACKAGE OUTLINE, 6, 8 & 10L, TDFN, EXPOSED PAD, 3x3x0.80 mm
APPROVAL DOCUMENT CONTROL NO. REV.
2 2
21-0137
D
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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