Battery Removal During Charging; Pwm; Battery Identification - Nokia NSB-7 Series Service Manual

NSB-7
System Module

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 battery 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, maximum 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 overvolt-
age situation has occured.
VCH
(Standard
Charger)
VOUT

PWM

SWITCH
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
Figure 5: Output Overvoltage Protection When Battery Removed (in principle; not in time scale)
PWM
When a charger is used, the power switch is turned ON and OFF by the PWM input. PWM
rate is 1Hz. When PWM is HIGH, the switch is ON and the output current Iout = charger
current - CHAPS supply current. When PWM is LOW, the switch is OFF and the output
current Iout = 0. To prevent the switching transients inducing noise in audio circuitry of
the phone soft switching is used.

Battery Identification

Different battery types are identified by a pulldown resistor inside the battery pack. The
BSI line inside transceiver has a 100k pull-up to VBB. The MCU can identify the battery
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Vpor
Droop depends on load
& C in phone
VLIM
4V
Vstart
"1
"0
ON
OFF
1 2 3
ãNokia Mobile Phones Ltd.
PAMS Technical Documentation
Istart off due to VCH<Vpor
Vstarthys
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