ISL9204 Intersil Corporation, ISL9204 Datasheet - Page 7

• Manufacturer Part Number: ISL9204
• Description: High Input Voltage Charger
• Manufacturer: Intersil Corporation

Description
The ISL9204 charges a Li-ion battery with a constant current
(CC) or a constant voltage (CV). The constant current I
is set with the external resistor R
constant voltage is fixed at 4.2V. If the battery voltage is
below a typical 2.8V trickle-charge threshold, the ISL9204
charges the battery with a trickle current until the battery
voltage rises above the trickle charge threshold. When the
battery voltage reaches 4.2V, the charger enters a CV mode
and regulates the battery voltage at 4.2V to fully charge the
battery without the risk of over charge. Upon reaching an
end-of-charge (EOC) current, the charger indicates the
charge completion with the CHG pin, but the charger
continues to output the 4.2V voltage. Figure 12 shows the
typical charge profile and the EOC/reset event.
The EOC current level I
external resistor R
to LOW when the trickle charge starts and rises to HIGH at
the EOC. After the EOC is reached, the charge current has
to rise to typically 73% I
again, as shown in Figure 12. The current surge after EOC
can be caused by a load connected to the battery.
A thermal foldback function reduces the charge current
anytime when the die temperature reaches typically 115°C.
This function guarantees safe operation when the printed-
circuit board (PCB) is not capable of dissipating the heat
generated by the linear charger. The ISL9204 accepts an
input voltage up to 28V but disables charging when the input
voltage exceeds the OVP threshold, minimum 10V, to
protect against unqualified or faulty AC adapters.
PPR Indication
The PPR pin is an open-drain output to indicate the
presence of the AC adapter. Whenever the input voltage is
IMIN
(see Figure 9). The CHG signal turns
MIN
17% I
REF
CHG
4.2V
I
3.0V
is programmable with the
REF
REF
for the CHG signal to turn on
7
IREF
TRICKLE
(see Figure 9) and the
FIGURE 12. TYPICAL CHARGE PROFILE
CC
REF
ISL9204
INDICATION
I
higher than the POR threshold, the PPR pin turns on the
internal open-drain MOSFET to indicate a logic LOW signal,
independent on the EN-pin input. When the internal open-
drain FET is turned off, the PPR pin should leak less than
1µA current. When turned on, the PPR pin should be able to
sink at least 10mA current under all operating conditions.
The PPR pin can be used to drive an LED (see Figure 9) or
to interface with a microprocessor.
Power-Good Range
The power-good range is defined by the following three
conditions:
where the VOS is the offset voltage for the input and output
voltage comparator, discussed shortly, and the VOVP is the
overvoltage protection threshold given in the Electrical
Specification. All V
given in the Electrical Specification table. The charger will
not charge the battery if the input voltage is not in the
power-good range.
Input and Output Comparator
The charger will not be enabled unless the input voltage is
higher than the battery voltage by an offset voltage VOS.
The purpose of this comparator is to ensure that the charger
is turned off when the input power is removed from the
charger. Without this comparator, it is possible that the
charger will fail to power down when the input is removed
and the current can leak through the PFET pass element to
continue biasing the POR and the Pre-Regulator blocks
shown in the Block Diagram.
MIN
CHG
1. VIN > VPOR
2. VIN - VBAT > VOS
3. VIN < VOVP
CURRENT
CHARGE
VOLTAGE
CHARGE
CV
POR
, V
OS
, and V
73% I
TIME
REF
OVP
have hysteresis, as
October 4, 2005
FN9207.0