Reference

Voltage

+

−

+

−

R

S

Q

+

−

Vs = 500 mV Typ

RESET

GND

CT

SENSE

VCC

ICT (A)

High:

On

IS (A)

Copyright © 2016, Texas Instruments Incorporated

10

TL7700

SLVS220G – JULY 1999 – REVISED AUGUST 2016

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Copyright © 1999–2016, Texas Instruments Incorporated

8 Detailed Description

8.1 Overview

The TL7700 is a bipolar integrated circuit designed for use as a reset controller in microcomputer and

microprocessor systems. The SENSE voltage can be set to any value greater than 0.5 V using two external

resistors. The hysteresis value of the sense voltage also can be set by the same resistors. The device includes a

precision voltage reference, fast comparator, timing generator, and output driver, so it can generate a power-on

reset signal in a digital system.

The TL7700 has an internal 1.5-V temperature-compensated voltage reference from which all function blocks are

supplied. Circuit function is very stable, with supply voltage in the 1.8-V to 40-V range. Minimum supply current

allows use with ac line operation, portable battery operation, and automotive applications.

8.2 Functional Block Diagram

A.

ICT = 15 µA (Typ), Is = 2.5 µA (Typ)

8.3 Feature Description

8.3.1 Sense-Voltage Setting

The SENSE terminal input voltage, Vs, of the TL7700 typically is 500 mV. By using two external resistors, the

circuit designer can obtain any sense voltage over 500 mV. In Figure 18, the sensing voltage, Vs', is calculated

as:

Vs' = Vs × (R1 + R2)/R2

where

•

Vs = 500 mV typ at TA = 25°C

(1)

At room temperature, Vs has a variation of 500 mV ± 5 mV. In the basic circuit shown in Figure 18, variations of

[±5 ± (R1 + R2)/R2] mV are superimposed on Vs.