TPS795_15 Datasheet, PDF (11/33 Pages) Texas Instruments – TPS795 Ultralow-Noise, High-PSRR, Fast, RF, 500-mA Low-Dropout Linear Regulators

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TPS795
SLVS350I – OCTOBER 2002 – REVISED MAY 2015
7.3 Feature Description
7.3.1 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.
7.3.2 Start-Up
The TPS795 uses a start-up circuit to quickly charge the noise reduction capacitor, C_NR, if present (see
Functional Block Diagrams). This circuit allows for the combination of very low output noise and fast start-up
times. The NR pin is high impedance so a low leakage C_NR capacitor must be used; most ceramic capacitors are
appropriate for this configuration.
For the fastest start-up, apply V_IN first, and then drive the enable pin (EN) high. If EN is tied to IN, start-up is
somewhat slower. To ensure that C_NR is fully charged during start-up, use a 0.1-μF or smaller capacitor.
7.3.3 Undervoltage Lockout (UVLO)
The TPS795 uses an undervoltage lockout circuit to keep the output shut off until internal circuitry is operating
properly. The UVLO circuit has approximately 100 mV of hysteresis to help reject input voltage drops when the
regulator first turns on.
7.3.4 Regulator Protection
The TPS795 PMOS-pass transistor has a built-in back diode that conducts reverse current when the input
voltage drops below the output voltage (for example, during power down). Current is conducted from the output
to the input and is not internally limited. If extended reverse voltage operation is anticipated, external limiting
might be appropriate.
The TPS795 features internal current limiting and thermal protection. During normal operation, the TPS795 limits
output current to approximately 2.8 A. When current limiting engages, the output voltage scales back linearly until
the overcurrent condition ends. While current limiting is designed to prevent gross device failure, care should be
taken not to exceed the power dissipation ratings of the package. If the temperature of the device exceeds
approximately 165°C (T_sd), thermal-protection circuitry shuts it down. Once the device has cooled down to less
than approximately 140°C, regulator operation resumes.
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