CAT1232LP, CAT1832
5 V and 3.3 V Supply Monitor, Watchdog Timer,
Manual Reset, with Active High & Low Resets
FEATURES
Selectable reset voltage tolerance
— CAT1232LP for 5 V supply
— CAT1832 for 3.3 V supply
Selectable watchdog period:
150 ms, 600 ms or 1.2 s
Two reset outputs
— Active high, push-pull reset output
— Active low, open-drain reset output
(CAT1232LP)
— Active low, push-pull reset output (CAT1832)
Debounced manual push-button reset
Compact SOIC and MSOP packages
For Ordering Information details, see page 11.
DESCRIPTION
The CAT1232LP and CAT1832 microprocessor
supervisors can halt and restart a “hung-up” or
“stalled” microprocessor, restart a microprocessor
after a power failure, and debounce a manual/push-
button microprocessor reset switch. The devices are
drop in replacements for the Maxim/Dallas
Semiconductor DS1232LP and DS1832 supervisors
Precision reference and comparator circuits monitor
the 5 V or 3.3 V system power supply voltage, V
CC
.
During power-up or when the power supply falls
outside selectable tolerance limits, both the RESET
¯¯¯¯¯¯
and RESET become active. After the power supply
voltage rises above the RESET threshold voltage, the
reset signals remain active for a minimum of 250ms,
allowing the power supply and system processor to
stabilize. The trip-point tolerance input, TOL, selects
the trip level tolerance to be either 5% or 10% for the
CAT1232LP 5 V supply and 10% or 20% for the
CAT1832 3.3 V supply.
Each device has a push-pull, active HIGH reset
output. The CAT1232LP also has an open drain,
active LOW reset output while the CAT1832 also has
a push-pull, active LOW reset output.
A debounced manual reset input activates the reset
outputs and holds them active for a minimum period of
250 ms after being released.
Also included is a watchdog timer to reset a
microprocessor that has stopped due to a software or
hardware failure. Three watchdog time-out periods are
¯¯
selectable: 150 ms, 600 ms and 1.2 s. If the ST input
is not strobed low before the watchdog time out period
expires, the reset signals become active for a
minimum of 250 ms.
APPLICATIONS
Microprocessor Systems
Portable Equipment
Controllers
Single Board Computers
Instrumentations
Telecommunications
FUNCTIONAL DIAGRAM
V
CC
TOL
V
CC
Reference
40kΩ
PBRST
TD
ST
Push Button Debounce
Watchdog Timebase Selection
Watchdog Transition Detector
–
Tolerance Selection
+
RESET
(CAT1232LP)
RESET
RESET
(CAT1832)
Reset &
Watchdog Timer
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
1
Doc. No. MD-3018 Rev. F
CAT1232LP, CAT1832
PIN CONFIGURATION
SOIC 8 Lead
MSOP 8 Lead
PDIP 8 Lead
¯¯¯¯¯¯
PBRST
TD
TOL
GND
1
2
3
4
8
V
CC
¯¯
ST
¯¯¯¯¯¯
RESET
RESET
SOIC 16 Lead
NC
¯¯¯¯¯¯
PBRST
NC
TD
NC
TOL
NC
GND
1
2
3
4
5
6
7
8
16
15
14
NC
V
CC
NC
¯¯
ST
NC
¯¯¯¯¯¯
RESET
NC
RESET
CAT
7
6
5
CAT
13
12
11
10
9
PIN DESCRIPTION
Pin Number
8-Lead
Package
1
2
Pin Number
16-Lead
Package
2
4
Name
¯¯¯¯¯¯
PBRST
TD
Function
Debounced manual pushbutton reset input
Watchdog typical time delay selection:
a) t
TD
= 150 ms for TD = GND
b) t
TD
= 600 ms for TD = Open
c) t
TD
= 1200 ms for TD = V
CC
CAT1232LP TOL selects 5% (TOL = GND) or 10% (TOL = V
CC
) trip
point tolerance. CAT1832 TOL selects 10% (TOL = GND) or 20%
TOL = V
CC
) trip point tolerance.
Ground
Active HIGH reset output. RESET is active
1. If V
CC
falls below the reset voltage trip point
¯¯¯¯¯¯
2. If PBRST is low
¯¯
3. If ST is not strobed low before the timeout period set by TD expires.
4. During power-up.
Active LOW reset output. (See RESET)
Strobe Input
Power Supply
No internal connection
3
4
6
8
TOL
GND
5
9
RESET
6
7
8
11
13
15
1, 3. 5, 7, 10,
12, 14, 16
RESET
¯¯
ST
V
CC
NC
ABSOLUTE MAXIMUM RATINGS
(*)
Parameters
Voltage on V
CC
¯¯
Voltage on ST and TD
¯¯¯¯¯¯
Voltage on PBRST,
¯¯¯¯¯¯
RESETand RESET
Ratings
-0.5 to 7.0
-0.5 to V
CC
+ 0.5
-0.5 to V
CC
+ 0.5
Units
V
V
V
Parameters
Maximum Junction Temperature
Storage Temperature Range
Lead Soldering Temperature (10s)
Operating Temperature Range
Ratings
125
-65 to +150
300
-40 to +85
Units
ºC
ºC
ºC
ºC
Note:
* Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions outside of those listed in the operational sections of this
specification is not implied. Exposure to any absolute maximum rating for extended periods may affect device performance and reliability.
Doc. No. MD-3018 Rev. F
2
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
CAT1232LP, CAT1832
ELECTRICAL CHARACTERISTICS
Unless otherwise stated, 1.0 V - V
CC
- 5.5 V and over the operating temperature range of -40ºC to +85ºC.
All voltages are referenced to ground.
Symbol Parameter
V
CC
I
CC1
V
IH
V
IL
V
CCTP
V
CCTP
V
CCTP
V
CCTP
t
TD
t
TD
t
TD
V
OH
I
OH
I
OL
I
IL
R
PU
C
IN
C
OUT
t
PB
t
RST
t
ST
t
RPD
t
F
t
PDLY
t
RPU
t
R
Supply Voltage
Supply Current
¯¯¯¯¯¯
ST and PBRST Input High
Level
¯¯¯¯¯¯
ST and PBRST Input Low
Level
V
CC
Trip Point (TOL = GND)
V
CC
Trip Point (TOL = V
CC
)
V
CC
Trip Point (TOL = GND)
V
CC
Trip Point (TOL = V
CC
)
Watchdog Time-Out Period
Watchdog Time-Out Period
Watchdog Time-Out Period
Output Voltage
Output Current
Output Current
Input Leakage
Internal Pull-Up Resistor
Input Capacitance
Output Capacitance
¯¯¯¯¯¯
PBRST Manual Reset
Minimum Low Time
Reset Active Time
¯¯
ST Pulse Width
V
CC
Fail Detect to RESET or
¯¯¯¯¯¯
RESET
V
CC
= 5.5 V, CAT1232LP
V
CC
= 3.6 V, CAT1832
(5)
(6)
V
CC
= 5.5 V, CAT1232LP
V
CC
= 3.6 V, CAT1832
CAT1232LP
CAT1232LP
CAT1832
CAT1832
TD = GND
TD = V
CC
TD floating
I = -500 µA
(3)
Output = 2.4 V
(2)
Output = 0.4 V
(1)
(1)
10
-1.0
32
40
1.0
55
5
7
¯¯¯¯¯¯
PBRST = V
IL
(4)
20
250
20
5
20
20
250
0
600
1000
8
600
1000
4.50
4.25
2.80
2.47
62.5
500
250
V
CC
-0.5 V
4.62
4.37
2.88
2.55
150
1200
600
V
CC
-0.1 V
-350
2
V
CC
- 0.4 V
-0.3
Conditions
Min
1.0
35
20
Typ
Max
5.5
50
35
V
CC
+ 0.3 V
0.8
0.5
4.74
4.49
2.97
2.64
250
2000
1000
Units
V
µA
V
V
V
V
V
V
ms
ms
ms
V
µA
mA
µA
kΩ
pF
pF
ms
ms
ns
µs
µs
ms
ms
ns
V
CC
Slew Rate
¯¯¯¯¯¯
PBRST Stable LOW to RESET
¯¯¯¯¯¯
and RESET Active
V
CC
Detect to RESET or
t
RISE
= 5 µs
¯¯¯¯¯¯
RESET Inactive
V
CC
Slew Rate
4.25 V to 4.75 V
Notes:
¯¯¯¯¯¯
(1) PBRST is internally pulled HIGH to V
CC
through a nominal 40 kΩ resistor (RPU).
¯¯¯¯¯¯
(2) RESET is an open drain output on the CAT1232LP.
(3) RESET remains within 0.5 V of V
CC
on power-down until V
CC
falls below 2 V. RESET remains within 0.5 V of ground on power-down until
V
CC
falls below 2.0 V.
¯¯
(4) Must not exceed the minimum watchdog time-out period (t
TD
). The watchdog circuit cannot be disabled. To avoid a reset, ST must be
strobed.
(5) Measured with V
CC
≥
2.7 V.
(6) Measured with V
CC
< 2.7 V.
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
3
Doc. No. MD-3018 Rev. F
CAT1232LP, CAT1832
TYPICAL CHARACTERISTICS
For the CAT1232LP, V
CC
= 5 V and T
AMB
= 25ºC unless otherwise stated.
Threshold Voltage vs. Temperature (10% TOL)
4.450
THRESHOLD VOLTAGE (V)
Threshold Voltage vs. Temperature (5% TOL)
4.630
THRESHOLD VOLTAGE (V)
4.445
TOL = Vcc (10%)
4.440
4.625
TOL = GND (5%)
4.620
4.435
4.615
4.430
-50
0
50
100
4.610
-50
0
50
100
TEMPERATURE (°C)
TEMPERATURE (ºC)
Supply Current vs. Temperature
40
Reset Active Time vs. Temperature
800
RESET ACTIVE TIME (ms)
Vcc = 5.5V
SUPPLY CURRENT (mA)
30
Vcc = 4.5V
20
700
Vcc = 5.5V
600
Vcc = 4.5V
TD = open
500
10
400
0
-50
0
50
100
300
-50
0
50
100
TEMPERATURE (°C)
TEMPERATURE (°C)
Reset Active Time Waveform
Transient Response
Doc. No. MD-3018 Rev. F
4
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
CAT1232LP, CAT1832
APPLICATION INFORMATION
SUPPLY VOLTAGE MONITOR
Reset Signal Polarity and Output Stage Structure
¯¯¯¯¯¯
RESET is an active LOW signal. It is developed with
an open drain driver in the CAT1232LP. A pull-up
resistor is required, typical values are 10 kΩ to 50 kΩ.
The CAT1832 uses a CMOS push-pull output stage
¯¯¯¯¯¯
for the RESET.
RESET is an active High signal developed by a
CMOS push-pull output stage and is the logical
¯¯¯¯¯¯
opposite to RESET.
Trip Point Tolerance Selection
The TOL input is used to select the V
CC
trip point
threshold. This selection is made connecting the
TOL input to ground or V
CC
. Connecting TOL to
Ground makes the V
CC
trip threshold 4.62 V for the
CAT1232LP and 2.88 V for the CAT1832.
Connecting TOL to V
CC
makes the V
CC
trip threshold
4.37 V for the CAT1232LP and 2.55 V for the
CAT1832.
After V
CC
has risen above the trip point set by TOL,
¯¯¯¯¯¯
RESET and RESETremain active for a minimum time
period of 250 ms.
On power-down, once V
CC
falls below the reset
threshold the RESET outputs will remain active and
are guaranteed valid down to a V
CC
level of 1.0 V.
Tolerance
Select
Voltage
CAT1232LP
TOL = V
CC
CAT1232LP
TOL = GND
CAT1832
TOL = V
CC
CAT1832
TOL = GND
Trip Point
Tolerance
10 %
5%
20 %
10 %
Trip Point Voltage (V)
Min
4.25
4.50
2.47
2.80
Nominal
4.37
4.62
2.55
2.88
Max
4.49
4.74
2.64
2.97
Manual Reset Operation
¯¯¯¯¯¯
Push-button input, PBRST, allows the user to issue
reset signals. The pushbutton input is debounced and
is pulled high through an internal 40 kΩ resistor.
¯¯¯¯¯¯
When PBRST is held low for the minimum time of
20 ms, both resets become active and remain active
for a minimum time period of 250 ms after PBRST
returns high.
¯¯¯¯¯¯
No external pull-up resistor is required, since PBRST
is pulled high by an internal 40 kΩ resistor.
¯¯¯¯¯¯
PBRST can be driven from a TTL or CMOS logic line
or short-ed to ground with a mechanical switch.
Figure 1. Timing Diagram: Power Up
Figure 2. Timing Diagram: Power Down
t
F
V
CCTP(MAX)
V
CCTP
t
R
V
CCTP
V
CCTP(MAX)
V
CC
V
CCTP(MIN)
V
CCTP(MIN)
V
CC
t
RPU
V
OH
RESET
RESET
t
RPD
V
OL
RESET
RESET
V
OH
V
OL
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
5
Doc. No. MD-3018 Rev. F
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