ISL9219

FN6606 Rev 2.00

Page 7 of 12

April 7, 2010

Theory of Operation

The ISL9219 is an integrated charger for single-cell Li-ion or

Li-polymer batteries. The ISL9219 functions as a traditional

linear charger when powered with a voltage-source adapter.

When powered with a current-limited adapter, the chargers

minimizes the thermal dissipation commonly seen in

traditional linear chargers.

As a linear charger, the ISL9219 charges a battery in the

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

has 0.7% accuracy over the entire recommended operating

condition range. The charger always preconditions the

battery with a 85mA constant current at the beginning of a

charge cycle, until the battery voltage is verified to be above

preconditioning charge mode is named trickle mode. 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 +125°C to prevent further temperature rise. The

thermal foldback feature guarantees safe operation when

the printed circuit board (PCB) is space limited for adequate

thermal dissipation.

USB Compliant Current Setting

The ISL9219 is fully compliant with the USB electrical

specification when a USB port is used as the input source.

The input source type can be identified by the host controller.

When the USB connector is plugged in, the host controller

will identify the device during the enumeration process. The

host controller will further identify whether the USB port is a

high power port (500mA max current) or low power port

(100mA max current). The host controller will then drive the

AC_IN and USBI pins thru its GPIO pins, according to the

identification results.

If USB compliance is not required, the AC_IN pin can be

hard wired to VOUT so that the fast charge current is always

set by ISET pin.

Depending on the input source type, the charge current

during the constant current phase is:

ISET: determined by RISET if input is an AC adapter

ISET = 430mA if input is a high power USB port

ISET = 85mA if input is a low power port

Power-Good Range

The power-good range is defined by the following three

conditions:

1. VIN > VOVP

2. VIN - VBAT > VOS

3. VIN < VOVP

where the VOS is the offset voltage for the input and output

voltage comparator and the VOVP is the overvoltage

protection threshold given in the “Electrical Specification”

as given in the Electrical Specification table. If the input

voltage is not in the power-good range, the charger will not

charge the battery. If the input voltage is within the power

good range, the PG pin will be connected to VIN through an

internal P-Channel MOSFET with a 20mA current capability.

If the input voltage is not within the power-good range, the

PG will be switched off from VIN and turned into a high

impedance (floating) state. When an overvoltage condition

occurs, the ISL9219 enters the suspended state.

Timeout Function

The charger offers a safety timer for setting the maximum

charge time (TIMEOUT) limit to prevent charging a dead

battery for an extensively long time. The trickle mode is

limited to 1/8 of TIMEOUT limit. The charger automatically

re-charges the battery when the battery voltage drops below

a recharge threshold.

State Indication

Five indication pins, STAT1, STAT2, ACFLT, PG and TRKL

are available from the charger to indicate the charge status

and fault conditions. The STAT1 and STAT2 are configured

to indicate various charging condition as given by the true

table in Table 1:

A fault status is triggered under one of these conditions:

1. The TS pin voltage is outside the preset temperature

window

2. Timeout occurs before the EOC current has been

reached

The ACFLT pin indicates a faulty AC adapter condition. It is

an open drain output which turns off when there is an AC

fault, otherwise stays on. An AC fault condition is defined as

when VIN falls below VACFLT threshold (4.4V) or VIN goes

above VOVP (6.0V).

The TRKL pin indicates that the operation is in trickle charge

mode. It is an open drain output which turns on when the

operation is in trickle mode, otherwise turns off.

The PG pin indicates that VIN is within the power-good

range.

TABLE 1. STAT1 AND STAT2 TRUE TABLE

STAT1

STAT2

CHARGING CONDITION

L

L

Charging

L

H

Charge Complete and during Re-Charge

H

L

Fault

H

H

Suspend