TPS799L54, TPS799L57

SBVS191B – APRIL 2012 – REVISED AUGUST 2014

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7.3 Feature Description

7.3.1 Internal Current Limit

The TPS799Lxx internal current limit helps protect the regulator during fault conditions. In current limit mode, the

output sources a fixed amount of current that is largely independent of the output voltage. For reliable operation,

do not operate the device in a current-limit state for extended periods of time.

The PMOS pass element in the TPS799Lxx has a built-in body diode that conducts current when the voltage at

OUT exceeds the voltage at IN. This current is not limited; therefore, if extended reverse voltage operation is

anticipated, external limiting may be required.

7.3.2 Shutdown

The enable pin (EN) is active high and is compatible with standard and low-voltage TTL-CMOS levels. When

shutdown capability is not required, EN can be connected to IN.

7.3.3 Start Up

Functional Block Diagram). This circuit allows for the combination of very low output noise and fast start-up

appropriate for this configuration.

somewhat slower. The start-up switch is closed for approximately 135

during start-up, use a 0.01-

μF or smaller capacitor.

7.3.4 Undervoltage Lockout (UVLO)

The TPS799Lxx uses an undervoltage lockout circuit to keep the output shut off until internal circuitry is operating

properly. The UVLO circuit has a deglitch feature so that undershoot transients are typically ignored on the input

if these transients are less than 50

μs in duration.

7.4 Device Functional Modes

Driving EN over 1.2 V turns on the regulator. Driving EN below 0.4 V puts the regulator into shutdown mode,

thus reducing the operating current to 150 nA, nominal.

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