Datasheet

TPS77001, TPS77012, TPS77015, TPS77018, TPS77025
TPS77027, TPS77028, TPS77030, TPS77033, TPS77050
ULTRALOW-POWER 50-mA LOW-DROPOUT LINEAR REGULATORS
SLVS210D – JUNE 1999 – REVISED MAY 2001
11
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
The TPS770xx family of low-dropout (LDO) regulators have been optimized for use in battery-operated
equipment. They feature extremely low dropout voltages, low quiescent current (17 µA nominally), and enable
inputs to reduce supply currents to less than 1 µA when the regulators are turned off.
device operation
The TPS770xx 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
and, unlike a PNP transistor, it does not require increased drive current as output current increases. Supply
current in the TPS770xx 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 350 mA; 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 approximately 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 gate diode
that conducts reverse current when the input voltage level drops below the output voltage level.
A voltage of 1.7 V or greater on the EN input will disable the TPS770xx internal circuitry, reducing the supply
current to 1µA. A voltage of less than 0.9 V on the EN
input will enable the TPS770xx and will enable normal
operation to resume. The EN
input does not include any deliberate hysteresis, and it exhibits an actual switching
threshold of approximately 1.5 V.
A typical application circuit is shown in Figure 21.
C1
1 µF
†
TPS77012, TPS77015, TPS77018, TPS77025, TPS77027,
TPS77028, TPS77030, TPS77033, TPS77050 (fixed-voltage options).
NC/FB
OUT
1
3
IN
EN
GND
2
4
5
V
I
ESR = 0.2 Ω
V
O
4.7 µF
+
TPS770xx
†
Figure 21. Typical Application Circuit