ISL9219

FN6606 Rev 2.00

Page 8 of 12

April 7, 2010

Applications Information

Power on Reset (POR)

The ISL9219 resets as the input voltage rises above the

POR rising threshold. The internal oscillator starts to

oscillate, the internal timer is reset, and the charger begins

to charge the battery. The STAT pins, will indicate the

operating condition according to Table 1.

The ISL9219 has a typical rising POR threshold of 3.6V and

a falling POR threshold of 2.4V.

Pre-Charge

If the battery voltage is below the pre-charge threshold, the

ISL9219 charger delivers a small current to pre-charge the

battery until the voltage reaches the fast charge threshold

value. The pre-charge threshold is programmed by the

resistor connected between the PRECH pin and GND. If the

PRECH pin is left floating, a default value of 3.0V is used as

the pre-charge voltage.

Charge Cycle

A charge cycle consists of three charge modes: trickle mode,

constant current (CC) mode, and constant voltage (CV)

mode. The charge cycle always starts with the trickle mode

the trickle mode. The charger moves to the CC mode after

CV mode begins. Since the battery terminal voltage is

current is expected to decline as the cell voltage rises. After

for any input type, the ISL9219 indicates the end-of-charge

(EOC) with STAT1 and STAT2. The charging actually does

not terminate until the internal timer completes its length of

TIMEOUT in order to bring the battery to its full capacity.

The following events initiate a new charge cycle:

•POR

• A new battery being inserted (detected by TS pin)

• Recovery from an battery over-temperature fault

•The EN pin is toggled from HI to LO or from HI to floating

Recharge

After a charge cycle completes at a timeout event, charging

is prohibited until the recharge condition (VOUT < VRECH)

is met. Then the charging restarts with the timer reset to

zero. The STAT1 and STAT2 indication however, is

unchanged.

Internal Oscillator

The internal oscillator establishes a timing reference. The

oscillation period is programmable with an external timing

page 5. The oscillator charges the timing capacitor to 1.5V

and then discharges it to 0.5V in one period, both with 10µA

A 1nF capacitor results in a 0.2ms oscillation period. The

accuracy of the period is mainly dependent on the accuracy

of the capacitance and the internal current source.

Total Charge Time

The total charge time for the CC mode and CV mode is

limited to a length of TIMEOUT. A 22-stage binary counter

increments each oscillation period of the internal oscillator to

set the TIMEOUT. The TIMEOUT can be calculated as

Equation 4:

A 1nF capacitor leads to 14 minutes of TIMEOUT. For

example, a 15nF capacitor sets the TIMEOUT to be

3.5 hours. The charger has to reach the end-of-charge

condition before the TIMEOUT, otherwise, a TIMEOUT fault

is issued. The TIMEOUT fault latches up the charger. There

are two ways to release such a latch-up: either to recycle the

input power, or toggle the EN pin to disable the charger and

then re-enable it.

The trickle mode charge has a time limit of 1/8 TIMEOUT. If

TIMEOUT fault is issued and the charger latches up. Thus,

the charger can stay in trickle mode for no more than 1/8 of

TIMEOUT interval.

Monitoring Output Current thru ISET Pin

In addition to programming the fast charge current, the ISET

can be used to monitor the actual output current for the AC

adapter input current setting. During the constant current

phase, the ISET pin voltage is fixed at 2.4V. In this case, the

output current can be calculated by using 2.4V divided by

For USB input current setting, VISET can still be used to

monitor the charge current but since VISET is not used for

the close loop current regulation, to achieve a good

accuracy, an one-point calibration is required.

End-of-Charge (EOC) Current

charger starts to indicate the charge complete condition with

the indication pins. The charger actually does not terminate

charging until the end of the TIMEOUT interval, as described

for all input types, i.e. for AC adapter, USB high power and

USB low power.

0.2 10

TIME





=

onds

sec



(EQ. 3)

TIMEOUT

2

OSC

14

1nF

------------------



=



=

minutes



(EQ. 4)