CS8140/1
CS8140/1
5V, 500mA Linear Regulator with
ENABLE, RESET , and Watchdog
Description
The CS8140 is a 5V Watchdog
Regulator with protection circuitry and
three logic control functions that allow
a microprocessor to control its own
power supply. The CS8140 is designed
for use in automotive, switch mode
power supply post regulator, and bat-
tery powered systems.
Basic regulator performance character-
istics include a low noise, low drift, 5V
± 4% precision output voltage with low
dropout voltage (1.25V @ I
OUT
= 500mA)
and low quiescent current (7mA @ I
OUT
= 500mA). On board short circuit, ther-
mal, and overvoltage protection make it
possible to use this regulator in particu-
larly harsh operating environments.
The Watchdog logic function monitors
an input signal (WDI) from the micro-
processor or other signal source. When
the signal frequency moves outside
externally programmable window lim-
its, a RESET signal is generated
( RESET ). An external capacitor
(C
DELAY
) programs the watchdog win-
dow frequency limits as well as the
power on reset (POR) and RESET delay.
The RESET function is activated by any
of three conditions: the watchdog sig-
nal moves outside of its preset limits;
the output voltage drops out of regula-
tion by more than 4.5%; or the IC is in
its power up sequence. The RESET sig-
nal is independent of V
IN
and reliable
down to V
OUT
= 1V.
In conjunction with the Watchdog, the
ENABLE function controls the regula-
torÕs power consumption. The CS8140Õs
output stage and its attendant circuitry
are enabled by setting the ENABLE
lead high. The regulator goes into sleep
mode (I
OUT
= 250µA) when the
ENABLE lead goes low and the watch-
dog signal moves outside its preset
window limits. This unique combina-
tion of control functions in the CS8140
gives the microprocessor control over
its own power down sequence: i.e. it
gives the microprocessor the flexibility
to perform housekeeping functions
before it powers down.
The CS8141 has the same features as the
CS8140, except that the CS8141 only
responds to input signals (WDI) which
are below the preset watchdog frequen-
cy threshold.
Features
s
5V ± 4%, 500mA Output
Voltage
s
µP Compatible Control
Functions
Watchdog
RESET
ENABLE
s
Low Dropout Voltage
(1.25V @ 500mA)
s
Low Quiescent Current
(7mA @ 500mA)
s
Low Noise, Low Drift
s
Low Current SLEEP Mode
(I
Q
= 250µA)
s
Fault Protection
Thermal Shutdown
Short Circuit
60V Peak Transient
Voltage
Package Options
24 Lead SOIC Wide
NC
Delay
WDI
V
OUT
Sense
1
RESET
ENABLE
NC
V
IN
Gnd
NC
NC
NC
NC
NC
NC
NC
Block Diagram
VIN
Reference
& Bias
Overvoltage
Overtemperature
NC
NC
NC
NC
NC
NC
Gnd
Regulation
ENABLE
WDI
Control Logic
ENABLE
RESET
Delay
14 Lead PDIP
VOUT
Short Circuit
Undervoltage
*
*NOTE: shorted together
on 7 Lead TO-220
7 Lead TO-220
Tab (Gnd)
1
2
3
4
5
6
7
1
Delay
WDI
V
OUT
Sense
NC
NC
NC
1
RESET
ENABLE
V
IN
Gnd
NC
NC
NC
Sense
RESET
Gnd
Watchdog
V
IN
ENABLE
RESET
Gnd
Delay
WDI
V
OUT
Delay
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 2/23/99
1
A
¨
Company
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
