Thermal

Shutdown

UVLO

Current

Limit

3.3M

Ω

Overshoot

Detect

500k

1.193V

Bandgap

IN

EN

FB

OUT

GND

400

Ω

TPS799

www.ti.com

SBVS056K – JANUARY 2005 – REVISED JANUARY 2015

Functional Block Diagram (continued)

Figure 27. Adjustable-Voltage Versions

7.3 Feature Description

7.3.1 Internal Current Limit

The TPS799 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 TPS799 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 TPS799 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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