ISL6298_06 Datasheet, PDF (13/17 Pages) Intersil Corporation – Li-ion/Li-Polymer Battery Charger

ISL6298
Three types of events will result in the FAULT pin to indicate
a logic low signal. The following explains the causes and
consequences.
1. TEMP pin voltage out of window. This is caused by the
ambient temperature being out of the user-set window.
When this fault occurs, the charging is halted until the
temperature returns within the window.
2. TEMP pin voltage higher than the battery removal
threshold. This is caused by the removal of the battery
pack. The charger is disabled when the battery is
removed and enabled when the battery is re-inserted.
3. TIMEOUT fault during trickle mode or CC mode. The
charger is latched when this error occurs. This fault can
only be cleared by cycling the input power or the EN
input.
The STATUS pin indicates a logic low when a charge cycle
starts and indicates a high when the EOC conditions are
met. Once the EOC conditions are met, the STATUS signal
is latched to high until a new charge cycle.
Both the STATUS and the FAULT pin need be pulled up with
external resistors to the 2.8V from the V2P8 pin or the input
voltage. Table 2 summarizes the STATUS and FAULT pins.
TABLE 2. INDICATION PINS
FAULT STATUS
INDICATION
High High
Charge completed with no fault (Inhibit) or
Standby
High Low
Charging in one of the three modes
Low High
Fault
*Both outputs are pulled up with external resistors.
Shutdown
The ISL6298 can be shutdown by pulling the EN pin to
ground. When shut down, the charger draws typically less
than 30µA current from the input power and less than 3µA
current from the battery. The 2.8V output at the V2P8 pin is
also turned off. The EN pin needs be driven with an open-
drain or open-collector logic output, so that the EN pin is
floating when the charger is enabled.
Battery Leakage Current
The leakage current from the battery is different when the IC
is enabled and disabled. When the IC is disabled, due to
removing input power or pulling the EN pin to low, the
leakage current is less than 3µA. When the IC is enabled but
not charging (due to a fault condition, the battery removal, or
after termination), the leakage current is caused mainly by
an internal 75kΩ voltage divider for the output voltage feed-
back. The leakage current is approximately 56µA when the
battery voltage is 4.2V.
Applications Information
Capacitor Selection
Typically any type of capacitors can be used for the input
and the output. A minimum 1µF ceramic capacitor is
recommended to be placed very close to the charger input.
Higher value input decoupling capacitance helps the stable
operation of the charger.
The output capacitor selection is dependent on the
availability of the battery during operation. When the battery
is attached to the charger, the output capacitor can be any
ceramic type with the value higher than 1µF. However, if
there is a chance the charger will be used as a linear
regulator, a 10µF tantalum capacitor is recommended.
The V2P8 pin supplies power to the internal control circuit as
well as external circuits. A good decoupling to this pin is very
important to a reliable operation of the charger. It is
recommended to use a 1µF ceramic capacitor for this pin.
FAULT and STATUS Pull-Up Resistors
Both FAULT and STATUS pins are open-drain outputs that
need an external pull-up resistor. It is recommended that
both pins be pulled up to the input voltage or the 2.8V from
the V2P8 pin, as shown in the Typical Application Circuits. If
the indication pins have to be pulled up to other voltages, the
user needs to examine carefully whether or not the ESD
diodes will form a leakage current path to the battery when
the input power is removed. If the leakage path does exist,
an external transistor is required to break the path.
Figure 24 shows the implementation. If the FAULT pin is
directly pulled up to the VCC voltage (not shown in Figure
24), a current will flow from the VCC to the FAULT pin, then
through the ESD diode to the VIN pin. Any leakage on the
VIN pin, caused by an external or internal current path, will
result in a current path from VCC to ground.
VIN
R_LKG
EN
GND
ESD Diode
VCC
STATUS
VIN or
R₁
V2P8
VIN
Q₁
FAULT
Note:
R_LKG is approximately 240k when EN is floating and is
approximately 140k when the EN is grounded.
FIGURE 24. PULL-UP CIRCUIT TO AVOID BATTERY LEAKAGE
CURRENT IN THE ESD DIODES.
13
FN9173.4
March 9, 2006