TL7702A, TL7705A, TL7709A, TL7712A, TL7715A
SUPPLY-VOLTAGE SUPERVISORS
SLVS028H – APRIL 1983 – REVISED MAY 2003
description/ordering information (continued)
The TL77xxA family of integrated-circuit supply-voltage supervisors is designed specifically 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 V
CC
attains a value approaching 3.6 V. At this point (assuming that SENSE is above V
IT+
), 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, 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
C
T
: t
d
= 1.3
×
10
4
×
C
T
, where C
T
is in farads (F) and t
d
is in seconds (s).
During power down and when SENSE is below V
IT–
, the outputs remain active until V
CC
falls below 2 V. After
this, the outputs are undefined.
An external capacitor (typically 0.1
µF)
must be connected to REF to reduce the influence of fast transients in
the supply voltage.
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.
VCC
8
Reference
Voltage
CT
SENSE
3
7
R1
(see Note A)
≈100 µA
6
RESET
5
RESET
R2
(see Note A)
2
RESIN
1
GND
4
REF
NOTES: A. TL7702A: R1 = 0
Ω,
R2 = open
TL7705A: R1 = 7.8 kΩ, R2 = 10 kΩ
TL7709A: R1 = 19.7 kΩ, R2 = 10 kΩ
TL7712A: R1 = 32.7 kΩ, R2 = 10 kΩ
TL7715A: R1 = 43.4 kΩ, R2 = 10 kΩ
B. Resistor values shown are nominal.
2
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