MB3829 Datasheet, PDF (6/24 Pages) Fujitsu Component Limited. – System Power Supply IC for Mobile Telephone

MB3829
Function Descriptions
1. Power supply control section
(1) Reference voltage circuit
The reference voltage circuit generates a temperature- compensated, stable voltage (» 1.26 V). The generated
reference voltage is used as the power supply control section reference voltage or bias.
(2) Series regulator section
A 4 - channel series regulator incorporating a low - saturation output transistor is used. All four channels provide an
output voltage of 3.0 V. Their characteristics are described below.
REG1 is suitable for a microcontroller power supply because it is connected to a power - on reset circuit. It is
controlled by the ON/OFF switch section.
ON/OFF control of REG2 and REG3 is exercised independently by the CTL2 and CTL3 pins while REG1 is ON.
REG4 operates at all times and is therefore suitable for data backup.
REGs 1 through 4 incorporate an overcurrent - protection circuit (REG1 to REG3 » - 100 mA, REG4 » - 25 mA).
(3) Battery backup section
When the main battery is installed, the series regulator recharges a button - type lithium secondary battery, which is
often used to provide backup for clocks and memory. When the main battery is not installed, the backup battery
supplies power to clocks and the battery via a built - in diode. Since the recharging series regulator is set at 3.18 V,
this battery backup section is suitable for manganese and lithium batteries.
(4) ON/OFF switch section
When a time - setup capacitance and resistance are connected to the CT1 pin, the ON1 pin makes it possible to set
the power supply button activation time. This feature prevents turning ON a mobile telephone accidentally.
The ON2 and OFF pins provide a method of exercising direct ON/OFF control of the regulator.
ON time setting calculation formula: T_ON » - C_T1 x R_T1 x ln (1 - 1.26V/V_CC2)
(5) Momentary power - loss function and power - restoration section
When a time - setup capacitance and resistance are connected to the CT3 pin, a momentary Vcc loss, which may be
caused by battery replacement, etc., will be detected so as to deliver output to the TOUT pin. At power restoration,
the operating state before the momentary power loss is recovered.
After a momentary power loss, the CLR pin resets the prevailing state so that the momentary power - loss detection
circuit retains the latch circuit state.
Momentary power - loss detection time calculation formula: T_OFF » - C_T3 x R_T3 x ln (1 - (2.3V - 0.27V)/2.3V)
6