FN6606 Rev 2.00

Page 10 of 12

April 7, 2010

ISL9219

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Input and Output Capacitor Selection

A 0.47µF or higher value ceramic capacitor for the input is

recommended. Due to the inductance of the power leads of

the wall adapter or USB source, the input capacitor type

must be properly selected to prevent high voltage transient

during a hot-plug event. A tantalum capacitor is a good

choice for its high ESR, providing damping to the voltage

transient. Multi-layer ceramic capacitors, however, have a

very low ESR and hence when chosen as input capacitors, a

1

 series resistor is recommended, as shown in the “Typical

Application” schematic on page 5, to provide adequate

damping.

When the battery is attached to the charger, the output

capacitor can be any ceramic type with the value higher than

0.1µF. However, if there is a chance the charger will be used

as an LDO linear regulator, a 10µF tantalum capacitor is

recommended.

Board Layout Recommendations

The ISL9219 internal thermal foldback function limits the

charge current when the internal temperature reaches

approximately +125°C. In order to maximize the current

capability, it is very important that the exposed pad under the

package is properly soldered to the board and is connected

to other layers through thermal vias. More thermal vias and

more copper attached to the exposed pad usually result in

better thermal performance. On the other hand, the number

of vias is limited by the size of the pad. The exposed pad is

big enough for 5 vias.

State Diagram

The state diagram is shown in Figure 3. There area total of

5 states during a complete charging cycle: trickle charge, CC

charge, CV charge, charge complete/recharge, fault and

suspend. In the trickle mode, the ISL9219 charges the

battery in a trickle current. If VOUT reaches VMIN before the

trickle charge timeout interval, the operation will move to the

CC mode. Before entering the CC mode, the input source is

identified. The CC mode output current is set according to

the input type as described in “USB Compliant Current

Setting” on page 7. When the output voltage reaches the

4.2V final voltage, the operation will move CV mode, where

the battery is charged at a constant voltage. If the end-of-

charge current is reached before the timeout interval is

elapsed, the operation moves to charge complete state. The

charger continues to charge the battery until a timeout

condition is reached, then the charging will be terminated.

After the termination, if the output voltage drops below the

recharge threshold, a recharge starts and the timer is rest to

zero. The STAT1 and STAT2 indications, remains the same

as the charge complete state.

In the event that the timeout condition is reached before

EOC, the fault mode is entered. The fault mode can also be

triggered by an OTP event. To exit the fault mode, the input

power has to be removed and re-applied, or the EN pin is

toggled to HI and back to LO, then a new cycle starts.