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
CS8140/1
Absolute Maximum Ratings
Input Voltage
Operating Range .................................................................................................................................................-0.5 to +26V
Peak Transient Voltage (46V Load Dump @ 14V V
BAT
) ..............................................................................................60V
Electrostatic Discharge
(Human Body Model)...............................................................................................................................................4kV
WDI Input Signal Range ...............................................................................................................................................-0.3 to +7V
Internal Power Dissipation ..............................................................................................................................Internally limited
Junction Temperature Range (TJ) .......................................................................................................................-40¡C to +150¡C
Storage Temperature Range ................................................................................................................................-65¡C to +150¡C
Lead Temperature Soldering
Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260¡C peak
Reflow (SMD styles only) ......................................................................................60 sec. max above 183¡C, 230¡C peak
ENABLE .......................................................................................................................................................................-0.3V to V
IN
Electrical Characteristics:
7V ² V
IN
² 26V, 5mA ² I
OUT
² 500mA, -40ûC ² T
J
² +150ûC, -40ûC ² T
A
² 125ûC
unless otherwise specified
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
s
Output Stage (V
OUT
)
Output Voltage, V
OUT
Dropout Voltage (V
IN
- V
OUT
)
Line Regulation
Load Regulation
Output Impedance, R
OUT
Quiescent Current, (I
Q
)
Active Mode
Sleep Mode
Ripple Rejection
Current Limit
Thermal Shutdown
Overvoltage Shutdown
s
ENABLE
Threshold
HIGH
LOW
Threshold Hysteresis
V
OUT
³ 0.5V, (V
OUT(ON)
)
V
OUT
< 0.5V, (V
OUT(OFF)
)
(HIGH - LOW)
3.50
4.05
3.95
100
4.50
V
V
mV
V
OUT
< 1V
7V ² V
IN
² 26V
5mA < I
OUT
< 500mA
I
OUT
= 500mA
I
OUT
= 50mA,
7V ² V
IN
² 26V
V
IN
= 14V,
50mA ² I
OUT
² 500mA
500mA DC and 10mA AC ,
100Hz ²
f
² 10kHz
0 ² I
OUT
² 500mA, 7V ² V
IN
² 26V
I
OUT
= 0mA, V
IN
= 13V, ENABLE = 0V
7 ² V
IN
² 17V, I
OUT
= 250mA,
f
= 120Hz
60
700
150
30
4.8
5.0
1.25
5
5
200
5.2
1.50
25
80
V
V
mV
mV
m½
7.00
0.25
75
1200
180
34
15.00
0.50
mA
mA
dB
2000
38
mA
¡C
V
2
CS8140/1
Electrical Characteristics: continued
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
s
RESET
Threshold
HIGH V
R(HI)
LOW V
R(LOW)
Threshold Hysteresis(V
RH
)
Reset Output Leakage
RESET = HIGH
Output Voltage
Low(V
L(LOW)
)
Low (V
Rpeak
)
Delay Times
t
POR
t
WDI( RESET )
s
Watchdog
Input Voltage
HIGH
LOW
Input Current
Threshold Frequency
f
WDILOWER
f
WDI(UPPER)
**
WDI ² V
OUT
C
DELAY
= 0.1µF
64
218
77
262
96
326
Hz
Hz
2.0
0.8
0
10
V
V
µA
V
OUT
increasing
V
OUT
decreasing
(HIGH - LOW)
V
OUT
³ V
R(HI)
4.65
4.50
150
4.90
4.70
200
V
OUT
- 0.05
4.90
250
25
V
V
mV
µA
1V ² V
OUT
² V
R(LOW)
Rp = 2.7k½*
V
OUT
, Power up, Power down
C
DELAY
= 0.1µF
30.0
0.5
0.1
0.6
47.5
1.0
0.4
1.0
65.0
1.5
V
V
ms
ms
* R
P
is connected to RESET and V
OUT
.
** CS8140 only
To observe safe operating junction temperature, low duty cycle pulse testing is used on tests where applicable.
Package Lead Description
Package Lead #
Lead Symbol
Function
7 Lead
TO-220
1
2
3
24 Lead *
SOIC Wide
21
23
24
14 Lead
PDIP
12
13
14
V
IN
ENABLE
RESET
Supply voltage to IC, usually direct from the battery.
CMOS compatible logical input. V
OUT
is disabled when
ENABLE is LOW and WDI is beyond its preset limits.
CMOS compatible output lead. RESET goes low whenever
V
OUT
drops below 4.5% of its typical value for more than
2µs or WDI signal falls outside itÕs window limits.
Ground connection.
Timing capacitor for Watchdog and RESET functions.
CMOS compatible input lead. The Watchdog function mon-
itors the falling edge of the incoming digital pulse train. The
signal is usually generated by the system microprocessor.
Regulated output voltage, 5V (typ).
Kelvin connection which allows remote sensing of output
voltage for improved regulation.
No connection.
4
5
6
12, 20
2
3
11
1
2
Gnd
Delay
WDI
7
N/A
4
5
1,6-11,13-19,22
3
4
5-10
V
OUT
Sense
NC
* The CS8141 uses a fused lead package. Leads 6-8 and 17-19 are fused together through the lead frame. These leads are
electrically connected to IC ground and should be connected to system ground for a good thermal connection.
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