15

TPS791

www.ti.com

SLVS325D – MARCH 2001 – REVISED FEBRUARY 2018

Product Folder Links: TPS791

Submit Documentation Feedback

Copyright © 2001–2018, Texas Instruments Incorporated

7.4 Device Functional Modes

7.4.1 Normal Operation

The device regulates to the nominal output voltage under the following conditions:

•

The input voltage is at least as high as the |VIN(min)|

•

The input voltage magnitude is greater than the nominal output voltage magnitude added to the dropout

voltage

•

|VEN| < low-level enable pin input voltage (0.7 V)

•

The output current is less than the current limit

•

The device junction temperature is less than the maximum specified junction temperature

7.4.2 Dropout Operation

If the input voltage magnitude is lower than the nominal output voltage magnitude plus the specified dropout

voltage magnitude, but all other conditions are met for normal operation, the device operates in dropout mode. In

this mode of operation, the output voltage magnitude is the same as the input voltage magnitude minus the

dropout voltage magnitude. The transient performance of the device is significantly degraded because the pass

device (such as a bipolar junction transistor, or BJT) is in saturation and no longer controls the current through

the LDO. Line or load transients in dropout can result in large output voltage deviations.

7.4.3 Disabled

The device is disabled under the following conditions:

•

|VEN| > high-level enable pin input voltage (2 V)

•

The device junction temperature is greater than the thermal shutdown temperature

Table 1 shows the conditions that lead to the different modes of operation.

Table 1. Device Functional Mode Comparison

OPERATING MODE

PARAMETER

VIN

VEN

IOUT

TJ

Normal mode

|VIN| > { |VOUT(nom)| + |VDO|, |VIN(min)| }

|VEN| < 0.7 V

I OUT < ICL

T J < 125°C

Dropout mode

|VIN(min)| < |VIN| < |VOUT(nom)| + |VDO|

|VEN| < 0.7 V

—

TJ < 125°C

Disabled mode

(any true condition disables the device)

—

|VEN| > 2 V

—

TJ > 170°C