ISL6292D Просмотр технического описания (PDF) - Renesas Electronics

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ISL6292D

Li-ion/Li Polymer Battery Charger

Renesas Electronics 

ISL6292D

Theory of Operation

The ISL6292D is an integrated charger for single-cell Li-ion or

Li-polymer batteries. The ISL6292D functions as a traditional

linear charger when powered with a voltage-source adapter.

When powered with a current-limited adapter, the charger

minimizes the thermal dissipation commonly seen in traditional

linear chargers.

As a linear charger, the ISL6292D charges a battery in the

popular constant current (CC) and constant voltage (CV)

profile. The constant charge current IREF is programmable up

to 2A with an external resistor or a logic input. The charge

voltage VCH has 1% accuracy over the entire recommended

operating condition range. The charger always preconditions

the battery with 10% of the programmed current at the

beginning of a charge cycle, until the battery voltage is verified

to be above the minimum fast charge voltage, VMIN. This low-

current preconditioning charge mode is named trickle mode.

The verification takes 15 cycles of an internal oscillator whose

period is programmable with the timing capacitor. A thermal-

foldback feature removes the thermal concern typically seen in

linear chargers. The charger reduces the charge current

automatically as the IC internal temperature rises above 100°C

to prevent further temperature rise. The thermal-foldback

feature guarantees safe operation when the printed circuit

board (PCB) is space limited for thermal dissipation.

A TEMP pin monitors the battery temperature to ensure a safe

charging temperature range. The temperature range is

programmable with an external negative temperature

coefficient (NTC) thermistor. The TEMP pin is also used to

detect the removal of the battery.

The charger offers a safety timer for setting the fast charge

time (TIMEOUT) limit to prevent charging a dead battery for an

extensively long time. The TIMEOUT limit can be disabled as

Trickle

Mode

Constant Current

Mode

Constant Voltage

Mode

Inhibit

VIN

VCH

Input Voltage

Battery Voltage

VMIN

IREF

IREF/10

P1

P2

P3

Charge Current

Power Dissipation

needed by the TOEN pin. The trickle mode is limited to 1/8 of

TIMEOUT and cannot be disabled by the TOEN pin.

The charger automatically re-charges the battery when the

battery voltage drops below a recharge threshold. When the

wall adapter is not present, the ISL6292D draws less than 3A

current from the battery.

Three indication pins are available from the charger to indicate

the charge status. The V2P8 outputs a 2.8V dc voltage when

the input voltage is above the power-on reset (POR) level and

can be used as the power-present indication. This pin is

capable of sourcing a 2mA current, so it can also be used to

bias external circuits. The STAT1 pin is an open-drain logic

output that turns LOW when the battery is being charged and

turns HIGH when the EOC condition is qualified. The EOC

condition is: the battery voltage rises above the recharge

threshold and the charge current falls below a user-

programmable EOC current threshold. Once the EOC

condition is qualified, the STAT1 output rises to HIGH and is

latched. The latch is released at the beginning of a charge or

re-charge cycle. The STAT1 pin blinks when a fault occurs. The

blinking frequency of a TIMEOUT fault is twice as fast as a

temperature fault. The STAT2 pin behaves the same as the

STAT1 except that it blinks at one frequency only when any

fault occurs.

Figure 2 shows the typical charge curves in a traditional linear

charger powered with a constant-voltage adapter. From the top

to bottom, the curves represent the constant input voltage, the

battery voltage, the charge current and the power dissipation in

the charger. The power dissipation PCH is given by the

following equations:

PCH = VIN-VBAT  ICHARGE

(EQ. 1)

Trickle

Mode

VIN

VCH

VMIN

Constant Current

Mode

Input Voltage

Constant Voltage

Mode

Inhibit

Battery Voltage

IREF

ILIM

IREF/10

Charge Current

P1

Power Dissipation

P2

FIGURE 2. TYPICAL CHARGE CURVES USING A

CONSTANT-VOLTAGE ADAPTER

FN9166 Rev.0.00

July 2004

FIGURE 3. TYPICAL CHARGE CURVES USING A CURRENT-

LIMITED ADAPTER

Page 7 of 13

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