Startup

GND

REF

SW REG

Control

Current Sense

Voltage

Sense

Startup

Blocking Diode

SW IN

SW REG IN2

SERIES IN1

OUTPUT

GND (PWR)

SW CURRENT CTRL

3

1

5

6

8

7

4

2

+

+

+

–

+

–

TL499A

SLVS029H – JANUARY 1984 – REVISED NOVEMBER 2015

www.ti.com

7 Detailed Description

7.1 Overview

The TL499A provides an adjustable output voltage between 2.9 V and 30 V. The primary power source uses the

internal linear regulator to provide the output voltage. When the primary power source is removed, the secondary

power source is stepped up using the internal switching regulator to provide the output voltage.

7.2 Functional Block Diagram

7.3 Feature Description

The TL499A has an adjustable output voltage set by feedback provided to REF pin abs an adjustable switching

current is set by value of resistor on SW CURRENT CONTROL pin. The lower resistance provides increased

switching current.

Dual power supply inputs also provide protection against power faults on the main supply of the TL499A.

7.4 Device Functional Modes

The TL499A has two functional modes:

•

Linear voltage regulation when SERIES IN1 supply is present.

•

Step-up voltage regulation when SERIES IN1 supply is absent.

6

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