G9612 Datasheet, PDF (6/8 Pages) Global Mixed-mode Technology Inc – Low-Dropout, 500mA Linear Regulator with Reset

Global Mixed-mode Technology Inc.
Pin Description
G9612
PIN NO.
1
2
3
4
5
PIN NAME
V_IN
GND
V_OUT
C_D
RESET
PIN FUNCTION
Regulator Input. Supply voltage can range from 2.5V to 6V.
Ground
Regulator Output. Sources up to 500mA.
External Programmable time delay is set by the capacitor connect to C_D pin.
RESET Open-Drain Output remains low while V_IN is below the reset threshold,
and for delay time set by C_D after V_IN rises above the reset threshold.
－
＋
THERMAL
PROTECTION
1.24V
REFERENCE
VIN
MOSFET DRIVER
WITH FOLDBACK
CURRENT LIMIT
P
V_OUT
－
＋
R1
R2
GND
RESET
RD
CD
Figure 1. Functional Diagram
Detailed Description
The G9612 are low-dropout, low-quiescent current
linear regulators with reset function The regulator in
G9612 supply 3.4V, 3.3V or 2.5V output for load cur-
rents up to 500mA. The reset function detect V_IN. As
illustrated in Figure 1, they consist of a 1.24V refer-
ence, error amplifier, MOSFET driver, P-channel pass
transistor, and internal feedback voltage divider, reset
threshold comparator and time delay generator.
The 1.24V bandgap reference is connected to the er-
ror amplifier’s inverting input. The error amplifier com-
pares this reference with the feedback voltage and
amplifies the difference. The MOSFET driver reads the
error signal and applies the appropriate drive to the
P-channel pass transistor. If the feedback voltage is
lower than the reference, the pass transistor gate is
pulled lower, allowing more current to pass and in-
creasing the output voltage. If the feedback voltage is
too high, the pass transistor gate is pulled up, allowing
less current to pass to the output.
Additional blocks of linear regulator include a foldback
current limiter, reverse current protection, and thermal
sensor.
The G9612 also offer reset function to detect the level
of V_IN. They assert a reset signal whenever V_IN supply
voltage declines below a preset threshold (V_TH), keep-
ing it asserted for time delay set by capacitor con-
nected to C_D pin, after V_IN has resen above the high
reset threshold (V_TH + V_HYS). The RESET is an active
low, open-drain output.
Internal P-Channel Pass Transistor
The G9612 feature a 500mA P-channel MOSFET pass
transistor. This provides several advantages over similar
designs using PNP pass transistors, including longer
battery life. The P-channel MOSFET requires no base
drive, which reduces quiescent current considerably.
PNP based regulators waste considerable amounts of
current in dropout when the pass transistor saturates.
They also use high base-drive currents under large
loads. The G9612 do not suffer from these problems
and consume only 320µA of quiescent current.
Ver: 1.7
Apr 01, 2005
TEL: [phone]
http://www.gmt.com.tw
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