Battery Removal During Charging - Nokia NSB-6 Series Technical Documentation Manual

Pams, system module
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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 VLIM, CHAPS turns switch
OFF until the charger input has sunken below Vpor (nominal 3.0V, maxi-
mum 3.4V). MCU software will stop the charging (turn off PWM) when it
detects that battery has been removed. The CHAPS remains 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
Issue 1 06/2000
Droop depends on load
& C in phone
1
2
3
4
E Nokia Mobile Phones Ltd.
Istart off due to VCH<Vpor
Vstarthys
5
6
7
NSB–6
System Module
t
t
t
Page 15

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