˜

ª

º

ª

º

¬

¼

¬

¼

SS

SS

C

nF

5 t

ms

§

·

˜

¨

¸

©

¹

UV1

IN(off)

UV-FALLING

UV-HYST

UV1

UV2

R

V

V

1

I

R

R

§

·

¨

¸

©

¹

UV1

IN(on)

UV-RISING

UV2

R

V

V

1

R

13

LM5181-Q1

www.ti.com

SNVSBN6 – APRIL 2020

Product Folder Links: LM5181-Q1

Submit Documentation Feedback

Copyright © 2020, Texas Instruments Incorporated

Feature Description (continued)

where

•

•

(10)

where

•

•

(11)

emitter voltage drop (approximately 0.6 V at room temperature). If the EN/UVLO voltage is below this hard

shutdown threshold, the internal LDO regulator powers off, and the internal bias-supply rail collapses, shutting

down the bias currents of the LM5181-Q1. The LM5181-Q1 operates in standby mode when the EN/UVLO

voltage is between the hard shutdown and precision-enable thresholds.

8.3.6 Configurable Soft Start

The LM5181-Q1 has a flexible and easy-to-use soft-start control pin, SS/BIAS. The soft-start feature prevents

inrush current impacting the LM5181-Q1 and the input supply when power is first applied. This is achieved by

controlling the voltage at the output of the internal error amplifier. Soft start is achieved by slowly ramping up the

target regulation voltage when the device is first enabled or powered up. Selectable and adjustable start-up

timing options include a 6-ms internally-fixed soft start and an externally-programmable soft start.

The simplest way to use the LM5181-Q1 is to leave SS/BIAS open. The LM5181-Q1 employs an internal soft-

start control ramp and starts up to the regulated output voltage in 6 ms.

start time further reduces the supply current needed to charge the output capacitors while sourcing the required

load current. When the EN/UVLO voltage exceeds the UVLO rising threshold and a delay of 20 µs expires, an

(12)