PAMS Technical Documentation
System Module
NSB-7
Issue 1 06/00
ã
Nokia Mobile Phones Ltd.
Page 15
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.
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.
Figure 4: Output Overvoltage Protection (in principle; not in time scale)
Parameter
Symbol
LIM input
Min
Typ
Max
Unit
Output voltage cutoff limit (dur-
ing transmission or Li-battery)
VLIM
LOW
4.4
4.6
4.8
V
PWM (32Hz)
VOUT
VLIM
t
SWITCH
ON
OFF
VCH
t
VCH<VOUT
ON