ISL6297_07 Datasheet, PDF (11/16 Pages) Intersil Corporation – Li-ion/Li Polymer Battery Charger

ISL6297
V_IN
V2P9
EN
DT
Impedance
POR Threshold
500ms
Charge Cycle
Charge Cycle
RED
GRN
15 cycles to 1/8 TIMEOUT
V_SEN
2.8V min.
Recharge
15 cycles
I_CHG
I_MIN
TIMEOUT
I_MIN
FIGURE 6. OPERATION WAVEFORMS
Internal Oscillator
The internal oscillator establishes a timing reference. The
oscillation period is programmable with an external timing
capacitor, C_TIME, as shown in Typical Applications. The
oscillator charges the timing capacitor to 1.5V and then
discharges it to 0.5V in one period, both with 10μA current.
The period T_OSC is:
T_OSC = 0.2 × 10⁶ × C_TIME
( sec onds)
(EQ. 6)
A 15nF capacitor results in a 3ms oscillation period. The
accuracy of the period is mainly dependent on the accuracy
of the capacitance and the internal current source.
Total Charge Time and C_TIME Selection
The time allowed for the battery to charge before an end of
charge indication is limited to the duration of the TIMEOUT
counter. The TIMEOUT period can be calculated by:
TIMEOUT=
14 × -^C----^T----^I--^M----^E--
1nF
(minutes)
(EQ. 7)
where C_TIME is the timing capacitor shown in the Typical
Application circuit. A 1nF capacitor leads to 14 minutes of
TIMEOUT. For example, a 15nF capacitor sets the
TIMEOUT to be 3.5 hours. The EOC indication goes active
when the TIMEOUT counter expires, even if the battery has
not reached full charge. At this point, if the voltage is above
4.05V, the recharge mechanism will continue to charge the
cell until the current drops below I_MIN. If the TIMEOUT
counter expires before the battery reaches 4.05V, then the
end of charge indication goes active, but the charger turns
off. The charger cannot leave this condition without toggling
the enable pin or cycling the power.
The trickle mode charge has a time limit of 1/8 TIMEOUT. If
the battery voltage does not reach V_MIN within that time
period, a TIMEOUT fault is issued and the charger turns off
with a flashing Yellow LED indicator. The charger stays in
trickle mode for at least 15 cycles of the internal oscillator
and, at most, 1/8 of TIMEOUT.
Once the ISL6297 detects that the battery reaches the EOC
condition, it resets the TIMEOUT counter. At the end of this
TIMEOUT period, the charger turns off and does not start
again until the battery reaches a recharge condition.
Recharge Threshold
Once the charger reaches an end of charge condition and
the charger turns off, if the battery voltage drops below the
recharge threshold given in the Electrical Specification table,
the charger starts a re-charge cycle. This is identical to an
inital charge cycle, except the indicator remains green.
LED Indications
The LED indicators show a number of conditions. On initial
power on reset, the LEDs sequence through red, green and
yellow. Once the charge begins, the ISL6297 pulls the RED
pin low to drive a red indicator. Once the charge properly
11
FN9215.1
March 20, 2007