8 Detailed Description

8.1 Overview

The TL7702B, TL7705B, and TL7733B are integrated-circuit supply-voltage supervisors designed for use as

reset controllers in microcomputer and microprocessor systems. The supply-voltage supervisor monitors the

supply for undervoltage conditions at the SENSE input. During power up, the RESET output becomes active

(low) when VCC attains a value approaching 1 V. As VCC approaches 3 V (assuming that SENSE is above VT+),

the delay-timer function activates a time delay, after which outputs RESET and RESET go inactive (high and low,

respectively). When an undervoltage condition occurs during normal operation, outputs RESET and RESET go

active. To ensure that a complete reset occurs, the reset outputs remain active for a time delay after the voltage

at the SENSE input exceeds the positive-going threshold value. The time delay is determined by the value of the

external capacitor CT : td ≈ 2.6 × 104 × CT , where CT is in farads (F) and td is in seconds (s).

An external capacitor (typically 0.1 µF) must be connected to REF to reduce the influence of fast transients in

the supply voltage.

8.2 Functional Block Diagram

The functional block diagram is shown for illustrative purposes only; the actual circuit includes a trimming

network to adjust the reference voltage and sense-comparator trip point.

+

±

+

±

SENSE

CT

VCC

3

7

RESIN

2

GND

4

R1

(see Note 1)

R2

(see Note 1)

Reference

Voltage 1

VX

Reference

Voltage 2

8

1

6

5

RESET

RESET

REF

Copyright © 2016, Texas Instruments Incorporated

TL7702B, TL7705B, TL7733B

SLVS037O – SEPTEMBER 1989 – REVISED DECEMBER 2020

www.ti.com

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