6

FN9184.0

March 17, 2005

GND (Pin 8)

System ground.

ICDL (Pin 9)

The ICDL pin has two functions. The first function is to

program the cradle charge current during the constant-

current mode. The voltage of this pin is 1.22V during the

constant-current mode of the cradle charger. The constant-

current mode current is programmed by the following

equations:

(see the Typical Application).

It is recommended that the charge current be programmed

in the range of 350mA to 650mA.

The second function of the ICDL pin is to monitor the actual

The cradle charge current should be programmed equal or

higher than the USB current; otherwise, the ICDL pin voltage

will be higher than 1.22V during the constant current mode

when the USB charger is working. The charger still works

properly but the accuracy of the current monitoring voltage

degrades and saturates at approximately 2.1V.

BAT (Pin 10)

Charger output pin. Connect this pin to the battery pack or

the battery cell. A 1µF or larger value ceramic capacitor is

recommended for decoupling. The charger relies on the

battery for stability so a battery should always be connected

to the BAT pin.

Description

The ISL6299 is designed for a single-cell Li-ion or Li-polymer

battery charging circuit that accepts both a USB port and a

desktop cradle as its power source. While the charge current

from the USB input source is fixed at 380mA, the charge

current from the cradle input is programmable between 0.1A

current is fixed at typically 80mA for the USB input and

Input Auto Selection

When both input sources are present, the charger selects

only one power source to charge the battery. When the

CRDL input is higher than the POR threshold, CRDL is

selected as the power source. Otherwise the USB input is

selected. If the CRDL input voltage is below the battery

voltage but the USB input voltage is higher than the battery

voltage, then the USB input is used to charge the battery.

The control circuit always breaks both internal power

devices before switching from one power source to the other

to avoid a cross conduction of both power MOSFETs.

USB Charge Current

When the USB port is selected as the power source, the

charge current enabled by the logic input at the USBON pin.

When the USBON is driven to logic LOW, the charger is

disabled. When the USBON is driven to logic HIGH, the

charge current is fixed at a typical value of 380mA. Thus for

the USB input, the USBON pin has a similar function as the

EN pin. The following table describes the USB charge

control by both the USBON pin and EN pin:

The USBON pin is equivalent to a logic LOW when left

floating. Typically the P-channel MOSFET for the USB input

380mA charge current, the typical head room is 260mV.

Thus, if the input voltage drops to a level that the voltage

difference between the USB pin and the BAT pin is less than

current; and the charger drops out the constant current

regulation.

Cradle Charge Current

The cradle charge current is enabled by the EN pin only, the

USBON pin has no control on the cradle charge current. The

cradle charge current is programmed with the external

resistor connected between the ICDL pin and the GND pin.

The current can be calculated with one of the equations

given in the ICDL pin description. Two equations are used

for the cradle current calculation, each corresponds to a

P-channel MOSFET for the CRDL input is 600m

Ω at room

temperature. When the head room between the input and

output voltages is small, the actual charge current, similar to

hand, if the head room between the input and output

voltages is large, the charge current may be limited by the

thermal foldback threshold.

Floating Charge Voltage

The floating voltage during the constant voltage phase is

4.2V. The floating voltage has an 1% accuracy over the

ambient temperature range of -40°C to 70°C.

16685.5

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21242.1

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TABLE 1. USB CHARGE CONTROL

EN = LOW

EN = HIGH

USBON = LOW

Disabled

Disabled

USBON = HIGH

Enabled

Disabled

ISL6299