Startup Charging; Battery Overvoltage Protection - Nokia Mobile Phones NSE-5 Series Service Manual

NSE–5
System Module

Startup Charging

When a charger is connected, the CHAPS is supplying a startup current
minimum of 130mA to the phone. The startup current provides initial
charging to a phone with an empty battery. Startup circuit charges the
battery until the battery voltage level is reaches 3.0V (+/– 0.1V) and the
CCONT releases the PURX reset signal and program execution starts.
Charging mode is changed from startup charging to PWM charging that is
controlled by the MCU software. If the battery voltage reaches 3.55V
(3.75V maximum) before the program has taken control over the charging,
the startup current is switched off. The startup current is switched on
again when the battery voltage is sunken 100mV (nominal).
Parameter
VOUT Start– up mode cutoff limit
VOUT Start– up mode hysteresis
NOTE: Cout = 4.7 uF
Start–up regulator output current
VOUT = 0V ... Vstart

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 different
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.
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Table 6.
Symbol Min
Vstart 3.45
Vstarthys 80
Istart 130
Table 7.
Symbol LIM input
VLIM1 LOW
VLIM2 HIGH
Technical Documentation
Typ Max
3.55 3.75
100 200
165 200
Min Typ Max
4.4 4.6 4.8
4.8 5.0 5.2
Issue 1 07/99
PAMS
Unit
V
mV
mA
Unit
V
V