Datasheet

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LTC1732-8.4

17328f

TYPICAL APPLICATIO

FEATURES

APPLICATIO S

DESCRIPTIO

Lithium-Ion Linear

Battery Charger Controller

The LTC

1732-8.4 is a complete constant-current/con-

stant-voltage linear charge controller for lithium-ion

(Li-Ion) batteries. Nickel-cadmium (NiCd) and nickel metal-

hydride (NiMH) batteries can also be charged with con-

stant current using external termination. Charge current

can be programmed with ±7% accuracy using external

sense and program resistors. An internal resistor divider

and precision reference set the final float voltage with ±1%

accuracy.

When the input supply is removed, the LTC1732-8.4

automatically enters a low current sleep mode, dropping

the battery drain current to 10µA. An internal comparator

detects the end-of-charge (C/10) condition while a pro-

grammable timer, using an external capacitor, sets the

total charge time. Fully discharged cells are automatically

trickle charged at 10% of the programmed current until

battery voltage exceeds 4.9V.

The LTC1732-8.4 begins a new charge cycle when a

discharged battery is connected to the charger or when the

input power is applied. In additon, if the battery remains

connected to the charger and the cell voltage drops below

8.05V, a new charge cycle will begin.

The LTC1732-8.4 is available in the 10-pin MSOP package.

■

Complete Linear Charger Controller for 2-Cell

Lithium-Ion Batteries

■

Preset Charge Voltage with ±1% Accuracy

■

Programmable Charge Current

■

C/10 Charge Current Detection Output

■

Programmable Charge Termination Timer

■

Small, Thin 10-Pin MSOP Package

■

Input Supply (Wall Adapter) Detection Output

■

8.8V to 12V Input Voltage Range

■

Automatic Sleep Mode When Input Supply

Is Removed (Only 10µA Battery Drain)

■

Automatic Trickle Charging of Low Voltage Cells

■

Programmable for Constant-Current-Only Mode

■

Battery Insertion Detect and Automatic Charging

of Low-Battery

■

Automatic Battery Recharge

■

Cellular Phones

■

Handheld Computers

■

Charging Docks and Cradles

■

Digital Cameras and Camcorders

, LTC and LT are registered trademarks of Linear Technology Corporation.

400mA 2-Cell 8.4V Li-Ion Battery Charger

= 10V

SENSE

DRV

SENSE

0.25Ω

PROG

19.6k

8.4V

Li-Ion

BATTERY

LTC1732-8.4

*SHUTDOWN INVOKED BY FLOATING THE PROG PIN

BAT

CHRG

MBRM120T3

10µF

1732-8.4 TA01

1µF

BAT

= 400mA

TIMER

0.1µF

Si9430DY

ACPR

TIMER

PROG

GND

SEL V

TIME (HOURS)

CHARGE CURRENT (mA)

400

300

200

100

1.5 2.5

1732-8.4 TA01b

0.5 1.0

2.0 3.0

CONSTANT

VOLTAGE

CONSTANT

CURRENT

TIMER

STOPS

CHRG

LED OFF

BATTERY VOLTAGE

400mA HR BATTERY

CHARGE CURRENT

BATTERY VOLTAGE(V)

Typical Li-Ion Charge Cycle

Summary of content (12 pages)

PAGE 1
LTC1732-8.4 Lithium-Ion Linear Battery Charger Controller U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Complete Linear Charger Controller for 2-Cell Lithium-Ion Batteries Preset Charge Voltage with ±1% Accuracy Programmable Charge Current C/10 Charge Current Detection Output Programmable Charge Termination Timer Small, Thin 10-Pin MSOP Package Input Supply (Wall Adapter) Detection Output 8.
PAGE 2
LTC1732-8.4 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Input Supply Voltage (VCC) ................................... 13.2V SENSE, DRV, BAT, SEL, TIMER, PROG, CHRG, ACPR ................. – 0.3V to 13.2V Operating Temperature Range (Note 2) .... – 40° to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec)..................
PAGE 3
LTC1732-8.4 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 9V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN IC/10 10% Charge Current Indication Level RPROG = 19.6k, RSENSE = 0.2Ω tTIMER TIMER Accuracy CTIMER = 0.
PAGE 4
LTC1732-8.4 U W TYPICAL PERFOR A CE CHARACTERISTICS Trickle Charge Threshold Voltage vs Temperature 110 110 VCC = 9V 4.93 CTIMER = 0.1µF VCC = 9V CTIMER = 0.1µF VBAT = 6V TA = 25° 105 4.92 4.91 tTIMER (%) 105 tTIMER (%) VTRKL (V) Timer Accuracy vs Temperature Timer Accuracy vs VCC 4.94 100 95 95 4.90 –50 –25 25 0 50 75 100 90 125 9 10 11 25 75 50 Battery Charge Current vs Temperature 540 530 IBAT (mA) 520 500 RPROG = 19.6K RSENSE = 0.2Ω VBAT = 6V VCC = 9V RPROG = 19.
PAGE 5
LTC1732-8.4 U U U PIN FUNCTIONS BAT (Pin 1): Battery Sense Input. A bypass capacitor of 10µF or more is required to keep the loop stable when the battery is not connected. A precision internal resistor divider sets the final float voltage. The resistor divider is disconnected in sleep mode to reduce the current drain on the battery. SEL (Pin 2): This pin must be connected to VCC. CHRG (Pin 3): Open-Drain Charge Status Output.
PAGE 6
LTC1732-8.4 W BLOCK DIAGRA VCC 8 + UNDERVOLTAGE LOCKOUT VCC = 8.2V 8.05V C5 – RSENSE SENSE + 3 + – 800Ω 80Ω C1 – CHRG 9 54mV + C4 – – C/10 STOP RECHRG C/10 + TIMER DRV CA SLP OSCILLATOR BAT LBO COUNTER 1 4.9V SEL* VREF 2 – ACPR + + C3 A1 – VA VCC – + 10 7 C2 + SHDN 4 720Ω UVLO ACPR – 35µA VREF 2.457V 2.5µA CHARGE 6 BATTERY CURRENT IBAT = (2.457V • 800Ω)/(RPROG • RSENSE) PROG GND 5 1732-8.4 BD RPROG *THE LTC1732-8.4 IS OPTIMIZED FOR 2-CELL (8.
PAGE 7
LTC1732-8.4 U OPERATIO The LTC1732-8.4 is a linear battery charger controller. The charge current is programmed by the combination of a program resistor (RPROG) from the PROG pin to ground and a sense resistor (RSENSE) between the VCC and SENSE pins. RPROG sets a program current through an internal trimmed 800Ω resistor setting up a voltage drop from VCC to the input of the current amplifier (CA).
PAGE 8
LTC1732-8.4 U W U U APPLICATIONS INFORMATION Charger Conditions The charger is off when any of the following conditions exist: the VCC pin is less than 8.2V, the dropout voltage (VCC – VBAT) is less than 54mV, or the PROG pin is floating. The DRV pin will be pulled to VCC and the internal resistor divider is disconnected to reduce the current drain on the battery.
PAGE 9
LTC1732-8.4 U U W U APPLICATIONS INFORMATION V+ VDD 8 VCC 400k CHRG 3 µPROCESSOR 2k LTC1732-8.4 OUT IN 1732-8.4 F01 Figure 1. Microprocessor Interface Table 1. Microprocessor Interface IN OUT CHARGE STATUS LOW HIGH Charge LOW Hi-Z C/10 HIGH Hi-Z Stop Charging When the LTC1732-8.4 is in charge mode, the CHRG pin is pulled low by an internal N-channel MOSFET. To detect this mode, force the digital output pin, OUT, high and measure the voltage at the CHRG pin.
PAGE 10
LTC1732-8.4 U W U U APPLICATIONS INFORMATION Constant-Current Only Mode VCC Bypass Capacitor The LTC1732-8.4 can be used as a programmable current source by connecting the TIMER pin to VCC. This is particularly useful for charging NiMH or NiCd batteries. In the constant-current only mode, the timer and voltage amplifier are both disabled. An external termination method is required to properly terminate the charge. Many types of capacitors can be used for input bypassing.
PAGE 11
LTC1732-8.4 U PACKAGE DESCRIPTIO MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.2 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.50 3.05 ± 0.38 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT WITHOUT EXPOSED PAD OPTION 0.254 (.010) 10 9 8 7 6 3.00 ± 0.102 (.118 ± .004) NOTE 4 4.88 ± 0.10 (.192 ± .004) DETAIL “A” 0.497 ± 0.076 (.0196 ± .003) REF 0° – 6° TYP GAUGE PLANE 1 2 3 4 5 0.53 ± 0.01 (.021 ± .
PAGE 12
LTC1732-8.4 U TYPICAL APPLICATIO 2-Cell 8.4V Linear Charger Using a PNP Pass Transistor VIN = 10V MBRM120T3 R2 2k CHARGE STATUS 2k 2 3 10 SEL VCC 9 CHRG SENSE LTC1732-8.4 7 DRV R1 10k RSENSE 0.25Ω TIMER CTIMER* 0.1µF PROG C3 1µF Q2 ZTX749 Q1 2N5087 ACPR BAT 4 C1 1nF 8 IBAT = 400mA 1 6 GND RPROG 19.