3

SS

SS

T

26 10

C

»

´

×

LOGIC

OSC

+

-

TYPE III

COMP

+

-

1.285V

&

Soft-Start

INT REG, EN,UVLO

GND

RT/SYNC

SW

BOOT

VIN

EN

FB

VIN

VOUT

Error Amp.

PWM Cmp.

ILimit

LM22673, LM22673-Q1

SNVS586O – SEPTEMBER 2008 – REVISED NOVEMBER 2014

www.ti.com

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 UVLO

The LM22673 also incorporates an input undervoltage lock-out (UVLO) feature. This prevents the regulator from

turning on when the input voltage is not great enough to properly bias the internal circuitry. The rising threshold is

4.3 V (typ) while the falling threshold is 3.9 V (typ).

7.3.2 Soft-Start

The soft-start feature allows the regulator to gradually reach steady-state operation, thus reducing start-up

stresses. The internal soft-start feature brings the output voltage up in about 500 µs. This time can be extended

by using an external capacitor connected to the SS pin. Values in the range of 100 nF to 1 µF are recommended.

The approximate soft-start time can be estimated from Equation 1.

(1)

Soft-start is reset any time the part is shut down or a thermal overload event occurs.

8

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