Battery Overvoltage Protection - Nokia NSB-7 Series Service Manual

PAMS Technical Documentation

Battery Overvoltage Protection

Output overvoltage protection is used to protect phone from damage. This function is
also used to define the protection cutoff voltage for the Lithium-Ion battery. The power
switch is immediately turned OFF if the voltage in VOUT rises above the selected limit
VLIM.
Parameter
Output voltage cutoff limit (dur-
ing transmission or Li-battery)
The voltage limit (VLIM1 or VLIM2) is selected by logic LOW or logic HIGH on the CHAPS
(N101) VLIM input pin.
When the switch in output overvoltage situation has once turned OFF, it stays OFF until
the battery voltage falls below VLIM and PWM = LOW is detected. The switch can be
turned on again by setting PWM = HIGH.
VCH
VCH<VOUT
VOUT
VLIM
SWITCH
PWM (32Hz)
Figure 4: Output Overvoltage Protection (in principle; not in time scale)
Issue 1 06/00
Symbol LIM input
VLIM LOW
ON
ãNokia Mobile Phones Ltd.
Min Typ
4.4 4.6
OFF ON
NSB-7
System Module
Max Unit
4.8 V
t
t
Page 15