ISL6291 Datasheet, PDF (7/11 Pages) Intersil Corporation – Li-ion/Li Polymer Linear Battery Charger

Description
Initialization
The ISL6291 initializes as the input voltage rises above the
power-on-reset (POR) threshold. Once the input voltage
reaches the POR level, the V2P8 pin outputs a 2.8V voltage.
This output voltage can be used as an adapter presence
indication and to bias the thermistor circuit. The POR takes
about 200µs. During the POR, the STATUS pin outputs a
logic HIGH signal, and the FAULT pin outputs a logic LOW
signal.
Operation States
Immediately after the POR, the charger enters a charge
state. A charge state always cycles through a trickle mode, a
constant-current mode, and a constant voltage mode, as
shown in Figure 1. If the battery completes a charge cycle
without a fault, the operation moves to the inhibit state,
waiting for the battery to be discharged to start another
charge cycle. Two types of fault may occur during a charge
cycle, namely, a TIMEOUT fault or a temperature fault (refer
to Functional Pin Description on TIME, TOEN, and TEMP
pins). If a fault occurs during the charge modes, the
operation enters the fault state. The charger is in a standby
state when the adapter is removed, or the EN pin of the IC is
pulled to LOW. In the standby state, the charger IC draws
less than 1µA current from the battery. The two open-drain
pins, STATUS and FAULT, indicate the operation states of
the charger (see Table 1).
TABLE 1. STATUS INDICATIONS
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.
The charger starts a new charge cycle when a wall adapter
is plugged in, a new battery is inserted, a battery voltage
drops below the re-charge threshold, a temperature fault
ends, or the EN pin is toggled from LOW to HIGH.
Trickle Charge Mode
A charge cycle always starts with the trickle charge mode.
The trickle charge mode is to pre-condition the battery and
prepare it for the fast charge (constant current or constant
voltage charge). It is not recommended to fast charge a
Li-ion battery when the battery is deeply discharged,
indicated by a low battery voltage. When the ISL6291 sees a
battery voltage lower than the V_MIN given in the Electrical
Specifications, it forces 1/10 of the current in the constant
current mode into the battery. The charger stays in the trickle
mode until the battery voltage is above V_MIN for 15
consecutive oscillation cycles (T_OSC). The 15-cycle delay is
to avoid entering the constant current mode accidentally,
caused by any transient voltage spike on the battery pack
terminals. The charge time for the trickle mode is limited to
1/8 of the TIMEOUT interval (see TIME pin description and
Figure 1). If the trickle charge time takes longer than 1/8 of
the TIMEOUT interval, a TIMEOUT fault is issued and the
charger is latched. The minimum trickle charge time is 15
T_OSC, and the maximum time is 1/8 TIMEOUT. During the
trickle mode, the STATUS pin is set to logic LOW, and the
FAULT pin is set to logic HIGH.
Constant Current Charge Mode
The battery is charged with a constant current programmed
by the IREF pin resistor (see IREF pin description) during
the constant current mode. The constant current is trimmed
to 10% accuracy. The battery voltage rises towards the
charge termination voltage V_CH in this mode. The constant
current mode ends when the battery voltage reaches V_CH.
The internal clock counter limits the maximum time for the
constant current mode to the TIMEOUT interval. The counter
is reset at the beginning of the this charge mode. If the
V_CH
V_RECHRG
V_MIN
I_REF
Trickle time
< 1/8 TIMEOUT
TIMEOUT
I_REF/10
0
I_MIN
0
Trickle
Mode
Constant Current Constant Voltage
Mode
Mode
TIME
Inhibit _Trickle CC CV
Mode ^{Mode Mode}
FIGURE 1. MODES OF OPERATION
7
FN9102.2
May 2, 2005