Nokia 8550 Service Manual
NSM–3/3D
System Module
PAMS Technical Documentation
Page 17
Issue 4 02/2002
Nokia Corporation
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.
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.
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.
PWM
t
VOUT
t
4V
VLIM
”1”
”0”
SWITCH
t
ON
OFF
2
1.
1
Battery removed, (standard) charger connected, VOUT rises (follows charger voltage)
2. VOUT exceeds limit VLIM(X), switch is turned immediately OFF
3.
3.
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).
output). When VCH > Vpor and VOUT < VLIM(X) –> switch turned on again (also PWM
is still HIGH) and VOUT again exceeds VLIM(X).
4
4. Software sets PWM = LOW –> CHAPS does not enter PWM mode
Vstart
5
5. PWM low –> Startup mode, startup current flows until Vstart limit reached
VCH
(Standard
Charger)
(Standard
Charger)
Vpor
Vstarthys
Droop depends on load
Istart off due to VCH<Vpor
& C in phone
6
6. VOUT exceeds limit Vstart, Istart is turned off
7. VCH falls below Vpor
7