Battery Removal During Charging - Nokia NSE-6 SERIES Service Manual

PAMS
Technical Documentation

Battery Removal During Charging

Output overvoltage protection is also needed in case the main battery is
removed when charger connected or charger is connected before the bat-
tery is connected to the phone.
With a charger connected, if VOUT exceeds VLIM1 (or VLIM2), CHAPS
turns switch OFF until the charger input has sunken below Vpor (nominal
3.0V, maximum 3.4V). MCU software will stop the charging (turn off
PWM) when it detects that battery has been removed. The CHAPS re-
mains in protection state as long as PWM stays HIGH after the output
overvoltage situation has occured.
VCH Vpor
(Standard
Charger)
VLIM
VOUT
4V
Vstart
PWM
"1"
"0"
ON
SWITCH
OFF
1. Battery removed, (standard) charger connected, VOUT rises (follows charger voltage)
2. VOUT exceeds limit VLIM(X), switch is turned immediately OFF
3. VOUT falls (because no battery) , also VCH<Vpor (standard chargers full–rectified
output). When VCH > Vpor and VOUT < VLIM(X) –> switch turned on again (also PWM
is still HIGH) and VOUT again exceeds VLIM(X).
4. Software sets PWM = LOW –> CHAPS does not enter PWM mode
5. PWM low –> Startup mode, startup current flows until Vstart limit reached
6. VOUT exceeds limit Vstart, Istart is turned off
7. VCH falls below Vpor
Original 08/98
Drop depends on load
& C in phone
1 2 3 4
Istart off due to VCH<Vpor
Vstarthys
5 6 7
NSE–6
System Module
t
t
t
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