9

FN6698.0

May 5, 2008

Figure 11 shows the typical charge profile including the

end-of-charge event.

Power Presence Indication

When either the USB or the cradle input voltage is above the

POR threshold, the PPR pin internal open-drain MOSFET

turns on indicating the presence of input power.

Power-Good Conditions

Even if there is power present, the charger will not deliver

any current to the output if the power-good conditions are

not met. The following two conditions together define the

power-good voltage range:

1. VCDRL or VUSB > VPOR

2. VCDRL or VUSB - VBAT > VOS

where VPOR is the power-on reset threshold and VOS is the

offset voltage for the input and output voltage comparator. All

of these thresholds have hysteresis, as given in the

“Electrical Specification” table on page 4. The charger will

not charge the battery if the input voltage does not meet the

power-good conditions.

Thermal Foldback (Thermaguard™)

The thermal foldback function reduces the charge current

when the internal temperature reaches the thermal foldback

threshold, which is typically +125°C. This protects the

charger from excessive thermal stress at high input voltages.

Input Bypass Capacitors

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, which provides damping to the voltage transient. Multi-

layer ceramic capacitors, however, have a very low ESR,

and hence, when chosen as input capacitors, a 1

Ω series

resistor must be used (as shown in the “Typical Applications”

on page 3) in order to provide adequate damping.

State Diagram

The state diagram for the charger functions is shown in

Figure 12. The diagram starts with the Power-Off state.

When at least one input voltage rises above the POR

threshold, the charge resets it self. If both input voltages are

above the POR threshold, the charger selects the CRDL

input as the power source. Then, if the EN pin is at a logic

HIGH voltage, the charger stays in disabled state. If the EN

pin goes LOW, the fast charge starts. Any time the EN pin

turns HIGH, the charger returns to the disabled state. When

the EOC condition is reached, the CHG will turn to logic

HIGH to indicate a charge complete status but the charge

will continue. The EOC condition is then latched until one of

the four re-charge conditions is encountered, as shown in

Figure 11.

TRICKLE

CC

CV

18

100

IMIN

4.2V

TIME

2.6V

CHARGE

CURRENT

CHARGE

VOLTAGE

3.9V

CHG

INDICATION

FIGURE 11. TYPICAL CHARGE CYCLE

ISL9214A