ILC1232
Impala Linear Corporation
1
mP Supervisory Circuit
(408) 574-3939
www.impalalinear.com
Sept 1999
Impala Linear Corporation
ILC1232 1.1
1
The ILC1232 is a multifunction circuit which monitors micro-
processor activity, external reset and power supplies in
microprocessor based systems. The circuit functions
include a watchdog timer, power supply monitor, micro-
processor reset, and manual pushbutton reset input.
The power supply line is monitored with a comparator and
an internal voltage reference. RST is forced low when an
out-of-tolerance condition exists and remains asserted for
at least 250ms after V
CC
rises above the threshold voltage
(4.5V or 4.75V). The RST pin will remain logic low with V
CC
as low as 1.4V.
The Watchdog input (ST) monitors mP activity and will
assert RST if no mP activity has occurred within the watch-
dog timeout period. The watchdog timeout period is selec-
table with nominal periods of 150, 600, or 1200 milliseconds.
Power OK/Reset Time Delay, 250ms min.
Watchdog Timer, 150ms, 600ms, or 1.2s typical
Precision Supply Voltage Monitor, Select Between 5% or
10% of Supply Voltage
18
A Supply Current
Debounced External Reset Input
8-Pin SO Package
Computers
Controllers
Critical Microprocessor Power Monitoring
Intelligent Instruments
Portable Equipment
ILC1232
V
CC
Top View
PBRST
RST
TD
2
1
8
6
RST
GND
ST
TOL
4
3
5
7
ETC1232N - 8 Lead Plastic DIP Package
ETC1232M - 8 Lead Plastic SOIC Package
Part
Package
Temp. Range
ILC1232N
8-Lead PDIP
-40C to +85C
ILC1232M
8-Lead SOIC
-40C to +85C
Ordering Information
ILC1232
P
V
CC
V
CC
V
CC
ST
RESET
PBRST
RST
TD
GND
TOL
I/O
Typical Circuit
Pin Package Configurations
General Description
Features
Applications
Parameter
Symbol
Ratings
Units
V
CC
-0.3 to 6.0
V
Terminal Voltage
All other inputs
-0.3 to (V
CC
+ 0.3)
V
Input Current
V
CC
250
mA
GND, All other
inputs
25
mA
Operating Temperature Range
T
A
-40 to +85
C
Storage Temperature Range
-65 to +150
C
Lead Temperature (Soldering, 10 sec.)
300
C
Power Dissipation
700
mW
Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure. Functionality at
or above these limits is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliabil-
ity. Operating ranges define those limits between which the functionality of the device is guaranteed.
V
CC
= 4.5 V to 5.5 V, T
A
= Operating Temperature Range, unless otherwise noted.
Parameter
Conditions
Min
Typ
Max
Units
Operating Voltage Range, V
CC
4.5
5.5
V
Supply Current, I
CC
(See Note 1)
18
40
A
ST and PBRST Input Levels
V
IH
(See Note 2)
V
IL
2.0
-0.3
V
CC
+ 0.3
0.8
V
Input Leakage, I
IL
1
A
Output Source Current, RST
V
OH
= 2.4V
1.0
10
mA
Output Sink Current, RST, RST
V
OL
= 0.4V
2.0
10
mA
V
CC
5% Trip Point (Reset Threshold Voltage)
TOL= GND
4.50
4.62
4.74
V
V
CC
10% Trip Point (Reset Threshold Voltage)
TOL= V
CC
4.25
4.37
4.49
V
Input Capacitance, ST, TOL
C
IN
(See Note 3)
5
pF
Output Capacitance, RST, RST
C
OUT
(See Note 3)
7
pF
PBRST Min. Pulse Width, t
PB
PBRST = V
IL
(See Note 4)
20
ms
PBRST Delay, t
PBD
1
4
20
ms
Reset Active Time, t
RST
250
610
1000
ms
ST Pulse Width, t
ST
20
ns
ST Timeout Period, t
TD
TD = 0V
TD = Open
TD = V
CC
62.5
250
500
150
600
1200
250
1000
2000
ms
V
CC
Fall Time, t
F
10
s
V
CC
Rise Time, t
R
0
ns
V
CC
Detect to RST Low and RST High, tRPD
V
CC
Falling at 1.66 mV/
s
50
150
s
V
CC
Detect to RST Open and RST Low, tRPU
V
CC
Rising (See Note 5)
250
610
1000
ms
Note 1: I
CC
is measured with outputs open and inputs within 0.5V of supply rails.
Note 2: PBRST has an internal 40k
(typical) pull-up resistor to V
CC
.
Note 3: Guaranteed by design.
Note 4: PBRST must be held low for a minimum of 20ms to guarantee a reset.
Note 5: RST has an open drain output.
ILC1232 mP Supervisory Circuit
Sept 1999
Impala Linear Corporation
2
(408) 574-3939
www.impalalinear.com
ILC1232 1.1
June 1999
Absolute Maximum Ratings
Electrical Characterisitcs
Pin
Number
Pin
Name
Description
1
PBRST
Pushbutton reset input. This input is debounced and can be driven with
external logic signals or a mechanical push button to actively force a reset.
All pulses less than 1ms in duration on the PBRST pin are ignored. Any
pulse with a duration of 20ms or greater is guaranteed to cause a reset.
2
TD
Time delay input. This input selects the timebase used by the watchdog
timer. When TD = 0V, the watchdog timeout period is set to a nominal
value of 150ms, when TD = open, the watchdog timeout period is set to a
nominal value of 600ms and when TD = V
CC
, the watchdog timeout period
is 1.2 sec nominally.
3
TOL
Tolerance select input. Selects whether 5% or 10% of V
CC
is used as the
reset threshold voltage. When TOL = 0 V, the 5% tolerance level is
selected and when TOL = V
CC
, a 10% tolerance level is selected.
4
GND
Ground pin, 0V reference.
5
RST
RST is asserted high if either V
CC
goes below the reset threshold, the
watchdog times out or PBRST is pulled low for a minimum of 20ms. RST
remains asserted for one reset timeout period after V
CC
exceeds the reset
threshold or after the watchdog times out or after PBRST goes high.
6
RST
RST is asserted low if either V
CC
goes below the reset threshold, the
watchdog times out or PBRST is pulled low for a minimum of 20ms. RST
remains asserted for one reset timeout period after V
CC
exceeds the reset
threshold or after the watchdog times out or after PBRST goes high.
Open-drain output.
7
ST
Input to the watchdog timer. If ST does not see a transition from high to
low within the watchdog timeout period, RST and RST will be asserted.
8
V
CC
Power supply input, 5V.
8
1
Reset
Generator
6
4
-
+
V
CC
ST
RST
GND
3
7
2
Trip Point
Select
Ref
Manual Reset
Debounce
Watchdog
Timer
Timeout
Select
5
RST
TOL
PBRST
TD
ILC1232 mP Supervisory Circuit
Sept 1999
Impala Linear Corporation
3
(408) 574-3939
www.impalalinear.com
ILC1232 1.1
June 1999
Pin Functions
Block Diagram
Power Monitor
The RST and RST pins are asserted whenever V
CC
falls
below the reset threshold voltage set by the TOL pin. A 5%
tolerance level (4.62V reset threshold voltage) can be
selected by connecting the TOL pin to ground or a 10% tol-
erance (4.37V reset threshold voltage) can be selected by
connecting the TOL pin to V
CC
. The reset pins will remain
asserted for a period of 250ms after V
CC
has risen above
the reset threshold voltage. The reset function ensures the
microprocessor is properly reset and powers up into a
known condition after a power failure. RST will remain valid
with V
CC
as low as 1.4V.
RST
t
PDLY
t
RST
PBRST
RST
t
PB
Pushbutton Reset Input
The PBRST input can be driven with a manual pushbutton
switch or with external logic signals. The input is internally
debounced and requires an active low signal to force the
reset outputs into their active states. The PBRST input will
recognize any pulse that is 20ms in duration or greater and
will ignore all pulses that are less than 1ms in duration.
Watchdog Timer
The microprocessor can be monitored by connecting the ST
pin (watchdog input) to a bus line or I/O line. If a high-to-low
transition does not occur on the ST pin within the watchdog
timeout period set by the TD pin (see Table 1), the RST and
RST pins will be asserted resulting in a microprocessor
reset. RST and RST will remain asserted for 250ms when
this occurs. A minimum pulse of 75ns or any transition high-
to-low on the ST pin will reset the watchdog timer. The
watchdog timer will be reset if ST sees a valid transition
within the watchdog timeout period.
t
TD
TD Pin
Min.
Typ.
Max.
GND
62.5ms
150ms
250ms
Open
250ms
600ms
1000ms
V
CC
500ms
1200ms
2000ms
Industry P/N
ILC Direct
Replacement
DS1232LP
ILC1232N
DS1232LPS-2
ILC1232M
DS1232
ILC1232N
DS1232LPN
ILC1232N
DS1232LPSN-2
ILC1232M
DS1232N
ILC1232N
MAX1232CPA
ILC1232N
MAX1232CSA
ILC1232M
MAX1232EPA
ILC1232N
MAX1232ESA
ILC1232M
MAX1232C/D
ILC1232D
RST
t
RPD
V
CCTP
V
CCTP
t
RPU
V
CC
RST
t
SD
ST
t
TD
ILC1232 mP Supervisory Circuit
Sept 1999
Circuit Decription
Power-Up/Power-Down Sequence
Pushbutton Reset
Watchdog Input
Table 1: Watchdog Timeout Period
Alternate Cross Reference Guide
Impala Linear Corporation
4
(408) 574-3939
www.impalalinear.com
ILC1232 1.1
June 1999
0.260
0.240
0.019
0.013
0.260
0.240
0.260
0.240
0.260
0.240
0.260
0.240
0.260
0.240
0.260
0.240
0.260
0.240
Pin 1 identifier
0.197
0.190
0.155
0.150
0.244
0.228
0.069
0.053
0.011
0.004
0.060
0.040
0.019
0.013
0.050
0.016
0.012
0.009
0.8
M Package, 8-Pin Small Outline
N Package, 8-Pin Plastic Dual-In-Line
Devices sold by Impala Linear Corporation are covered by the warranty and patent indemnification provisions appearing
in its Terms of Sale only. Impala Linear Corporation makes no warranty, express, statutory, implied, or by description
regarding the information set forth herein or regarding the freedom of the described devices from patent infringement.
Impala Linear Corporation makes no warranty of merchantability or fitness for any purpose. Impala Linear Corporation
reserves the right to discontinue production and change specifications and prices at any time and without notice.
This product is intended for use in normal commercial applications. Applications requiring an extended temperature
range, unusual environmental requirements, or high reliability applications, such as military and aerospace, are specif-
ically not recommended without additional processing by Impala Linear Corporation.
Impala Linear Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in an
Impala Linear Corporation product. No other circuits, patents, licenses are implied.
Life Support Policy
Impala Linear Corporation's products are not authorized for use as critical components in life support devices or systems.
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use pro-
vided in the labelling, can be reasonably expected to result in a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reason-
bly expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
ILC1232 mP Supervisory Circuit
Sept 1999
Impala Linear Corporation
5
(408) 574-3939
www.impalalinear.com
ILC1232 1.1
June 1999
Packaging Information
Tape and Reel Information
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