Battery Overvoltage Protection - Nokia NSE–3 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 differ-
ent battery types (Li or Ni). The power switch is immediately turned OFF if
the voltage in VOUT rises above the selected limit VLIM1 or VLIM2.
Parameter
Output voltage cutoff limit
(during transmission or Li–
battery)
Output voltage cutoff limit
(no transmission or Ni–bat-
tery)
The voltage limit (VLIM1 or VLIM2) is selected by logic LOW or logic
HIGH on the CHAPS (N101) LIM– input pin. Default value is lower limit
VLIM1.
When the switch in output overvoltage situation has once turned OFF, it
stays OFF until the the battery voltage falls below VLIM1 (or VLIM2) and
PWM = LOW is detected. The switch can be turned on again by setting
PWM = HIGH.
VCH
VCH<VOUT
VOUT
VLIM1 or VLIM2
SWITCH
PWM (32Hz)
Original 11/97
Symbol LIM input
VLIM1
VLIM2
ON
Min Typ
LOW 4.4 4.6
HIGH 4.8 5.0
OFF ON
NSE–3
System Module
Max Unit
4.8 V
5.2 V
t
t
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