Datasheet

TPS76425, TPS76427, TPS76428, TPS76430, TPS76433
LOW-POWER LOW-NOISE 150-mA LOW-DROPOUT LINEAR REGULATORS
SLVS180B – MARCH 1999 – REVISED MAY 2001
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
The TPS764xx family of low-noise and low-dropout (LDO) regulators are optimized for use in battery-operated
equipment. They feature extremely low noise (50 µV), low dropout voltages, low quiescent current (140 µA),
and an enable input to reduce supply current to less than 2 µA when the regulator is turned off.
device operation
The TPS764xx uses a PMOS pass element to dramatically reduce both dropout voltage and supply current over
more conventional PNP-pass-element LDO designs. The PMOS pass element is a voltage-controlled device
which, unlike a PNP transistor, does not require increased drive current as output current increases. Supply
current in the TPS764xx is essentially constant from no-load to maximum load.
Current limiting and thermal protection prevent damage by excessive output current and/or power dissipation.
The device switches into a constant-current mode at approximately 1 A; further load reduces the output voltage
instead of increasing the output current. The thermal protection shuts the regulator off if the junction temperature
rises above 165°C. Recovery is automatic when the junction temperature drops approximately 25°C below the
high temperature trip point. The PMOS pass element includes a back diode that safely conducts reverse current
when the input voltage level drops below the output voltage level.
An internal resistor, in conjunction with external 0.01-µF bypass capacitor, creates a low-pass filter to further
reduce the noise. The TPS764xx exhibits only 50 µV of output voltage noise using 0.01 µF bypass and 4.7-µF
output capacitors.
A logic low on the enable input, EN, shuts off the output and reduces the supply current to less than 2 µA. EN
should be tied high in applications where the shutdown feature is not used.
A typical application circuit is shown in Figure 19.
C1
1 µF
†
TPS76425, TPS76427 TPS76430, TPS76433.
BYPASS
OUT
1
3
IN
EN
GND
2
4
5
V
I
CSR = 1 Ω
V
O
4.7 µF
+
TPS764xx
†
0.01 µF
+
Figure 19. Typical Application Circuit