MIC79110 Datasheet, PDF (10/12 Pages) Micrel Semiconductor – Simple 1.2A Linear Li-Ion Battery Charger

MIC79110
Simple Charger - External Trigger to Reset Charge
Cycle reset
Reset charge cycle.
200Ω
SD
GND
RSET REOC
VSENSE DEOC
VBAT ACHG
VIN
VIN
2kΩ
CDELAY
0.1µF
1MΩ
The V_IN voltage steps up to a voltage greater than V_BAT.
When Vin is below Vbat, the Ibat current is near zero and the
reverse shutoff circuit is turning the charge to the battery off.
The I_BAT slowly increases as V_IN rises above V_BAT. D_EOC is
pulled low when the Ibat current is above the Ieoc current set
by R_EOC. When the D_EOC is low, the shutdown pin is also
forced low and helps discharge C_SD. When the V_BAT reaches
the set voltage, the Ibat begins to slowly drop. When the Ibat
is less than the I_EOC threshold, the D_EOC output goes high
impedance, indicating end-of-charge. When an external sig-
nal is applied to the gate, the external N_CH pulls the SD and
DEOC pins to ground. This restarts the charging process.
Micrel
External Trigger to Reset Charge Cycle Reset
1 - V_IN steps up to a voltage greater than V_BAT.
2 - SD held low by C_SD until active high D_EOC pulls
shutdown low.
3 - Deoc releases SD, resistor pull-up from SD pin'vo
V_IN pulls V_SD to V_IN.
4 - An external signal applied to the gate of the
external N_CH pulls SD pin-to-ground.
5 - Ibattery is near zero (2 to 4µA) because V_IN is
below V_BAT and the reverse shutoff circuit is turn-
ing the charge to the battery off.
6 - I_BAT is decreased as V_BAT approaches V_BAT set
voltage. I_BAT decreases below the D_EOC threshold
and D_EOC is released high allowing V_SD to go high
7 - External N_CH turns part on, after a small delay I_BAT
turns on.
8 - Active high DEOC pin goes high because of
reverse shutoff. D_EOC remains high until I_BAT ex-
ceeds D_EOC threshold, then goes low.
9 - I_BAT decreases below (see #5) D_EOC threshold.
10 - Active low D_EOC is high because V_IN is below
V_BAT and reverse shutoff holds D_EOC comparator
off. As V_IN increases above V_BAT, the reverse
voltage shutoff turns off, D_EOC comparator be-
comes active. While I_BAT is below D_EOC threshold
D_EOC active low goes low, when I_BAT exceeds
D_EOC threshold I_BAT goes high.
11 - Legitimate Activation of active low D_EOC until SD
shuts down part and D_EOC AL (active low) goes
high.
VSD
1
2
Vin
Vbat set voltage
Vbat
SD threshold
2
3
Vgate
6
4
5
Ibattery
7
8
Active high DEOC pin
9
9
Active low DEOC pin
10
M9999-072004
10
July 2004