TC32M
ECONOMONITOR™ – 3-Pin System Supervisor with
Power Supply Monitor and Watchdog
Features:
• Incorporates the Functionality of the Industry
Standard TC1232 (Processor Monitor, Watchdog
and Manual Override Reset Controller) into a
Small, Lower Cost Package
• Guards Against Unstable Processor Operation
Resulting from Power “Brown-Out”
• Automatically Halts and Restarts an Out-of-
Control Microprocessor
• Output can be Wire-ORed, or Hooked to Manual
Reset Push-button Switch
• Space-Saving 3-Pin TO-92 or SOT-223 Package
General Description:
The TC32M is a fully-integrated processor supervisor
in a 3-pin package. It provides three important func-
tions to safeguard processor sanity: precision power
on/off Reset control, Watchdog Timer and external
Reset override.
On power-up, the TC32M holds the processor in the
Reset state for a minimum of 500 msec after V
DD
is
within tolerance to ensure a stable system start-up.
Microprocessor sanity is monitored by the on-board
Watchdog circuit. The microprocessor must provide a
high-to-low level shift (through an external resistor
divider) on the RS pin of the TC32M. Should the
processor fail to supply this signal within the specified
time-out period (typically 700 msec), an out-of-control
processor is indicated and the TC32M issues a
processor Reset as a result.
The output of the TC32M can be wire-ORed with a
push-button switch (or electronic signal) to override the
TC32M and unconditionally reset the processor. When
connected to a push-button switch, the TC32M
provides contact debounce.
The TC32M is packaged in a space-saving TO-92 or
SOT-223 package. It provides all of the functionality of
the industry standard TC1232 in a smaller, lower cost
configuration.
Applications:
•
•
•
•
•
•
All Microprocessor-Based Systems
Battery Powered Computers and Controllers
Automotive Systems
Intelligent Instruments
Critical Processor Monitoring
Embedded Controllers
Device Selection Table
Part Number
TC32MCDB
TC32MCZB
TC32MEDB
TC32MEZB
Package
SOT-223
TO-92
SOT-223
TO-92
Temp. Range
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
Package Type
1
2 3
V
DD
4
TC32MCDB
TC32MEDB
TC32MCZB
TC32MEZB
1
GND
GND
V
DD
RS
2
V
DD
3
RS
2001-2012 Microchip Technology Inc.
DS21402D-page 1
TC32M
Functional Block Diagram
V
DD
Typical Operating Circuit
5V
TC32M
V
REF1
R1, 10 kΩ
Watchdog
Timer
DV
Detector
Microcontroller
R2, 10 kΩ
PO.1
RS
RS
Reset
Reset
V
REF2
Delay
Timer
GND
TC32M
DS21402D-page 2
2001-2012 Microchip Technology Inc.
TC32M
1.0
ELECTRICAL
CHARACTERISTICS
*Stresses above those listed under “Absolute Maxi-
mum 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
above those indicated in the operation sections of the
specifications is not implied. Exposure to Absolute
Maximum Rating conditions for extended periods may
affect device reliability.
Absolute Maximum Ratings*
Supply Voltage (V
DD
to GND) .............................+6.0V
Input Voltage Any Pin..... (GND – 0.3V) to (V
DD
+0.3V)
Operating Temperature Range
TC32MC Package........................... 0°C to +70°C
TC32ME Package ........................ -40°C to +85°C
Storage Temperature Range ............. -65°C to +150°C
TC32M ELECTRICAL SPECIFICATIONS
Recommended DC Operating Conditions:
T
A
= -40°C
to
+85
°C unless otherwise noted.
Symbol
V
DD
V
IH
V
IL
Symbol
I
IL
I
OL
I
CC
V
STH
V
STL
V
RST
Symbol
C
IN
C
OUT
Symbol
t
RST
t
ST
t
TD
t
RPD
Note 1:
2:
Parameter
Supply Voltage
RS Input HIGH Level for PB
RS Input LOW Level for PB
Parameter
RS Input Leakage
RS Output Current
Operating Current
RS Strobe HIGH Level
RS Strobe LOW Level
Reset Threshold
Parameter
Input Capacitance
Output Capacitance
Parameter
Reset Active Time
RS Strobe Pulse Width
Watchdog Time-out Period
V
DD
Detect to RS LOW
No output load.
All voltages referenced to ground.
Min
4.5
2.0
—
Min
-1
2.0
—
(V
DD
– 0.5V)
2.00
4.25
Min
—
—
Min
500
500
500
—
Typ
—
—
—
Typ
—
10
50
—
—
—
Typ
—
—
Typ
700
—
700
—
Max
5.5
—
0.3
Max
+1
—
200
—
(V
DD
– 1.5V)
4.50
Max
5
7
Max
900
—
900
Units
V
V
V
Units
mA
mA
A
V
V
V
Units
pF
pF
Units
msec Figure
nsec Figure 3-1
msec Figure 3-1
nsec Figure 3-1
Test Conditions
V
OL
= 0.4V
Note 1
Figure 3-1
Figure 3-1
V
DD
Falling (Note
2,
Figure 3-3)
Test Conditions
Test Conditions
Test Conditions
DC Electrical Characteristics:
V
DD
= 4.5V to 5.5V,
T
A
= -40°C
to
+85
°C unless otherwise noted.
Capacitance Electrical Characteristics:
T
A
= 25°C
unless otherwise noted.
AC Electrical Characteristics:
T
A
= -40°C
to
+85
°C, V
DD
= 5V ±10%,
unless otherwise noted.
2001-2012 Microchip Technology Inc.
DS21402D-page 3
TC32M
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
Symbol
GND
Pin No.
(SOT-223, TO-92)
1
2
3
Description
Ground.
The +5V power supply input.
Reset/Strobe (Bidirectional). The open drain goes active if:
V
DD
falls below 4.5V nominal.
If pulled low by an external electronic signal or switch closure.
If the Watchdog is not strobed within the minimum Watchdog Time-out period.
During power-up and power-down.
In the Input mode, RS connects to a voltage level shift network (typically a resistor
divider to V
DD
.) The Watchdog Timer is reset when processor causes a voltage
level
V
STL
to be applied to RS.
The +5V power supply input (SOT-223 only).
V
DD
RS
4
V
DD
DS21402D-page 4
2001-2012 Microchip Technology Inc.
TC32M
3.0
DETAILED DESCRIPTION
t
ST
RS
V
STH
(Min)
V
ST
L (Max)
V
STL
(Min)
t
TD
Note:
t
TD
is the maximum elapsed time between strobes which
will keep the watchdog timer from forcing RS LOW.
(A Strobe is defined as a high-to-low transition from V
STH
to V
STL
).
The TC32M provides three important functions to
safeguard stable processor operation: precision pro-
cessor monitor, Watchdog sanity timer and external
override Reset control.
3.1
Processor Monitor
The RS pin is immediately driven low any time V
DD
is
below the nominal threshold voltage. As a result, this
pin is LOW when power is initially applied, holding the
processor in its Reset state. RS remains low for a
minimum of 500 msec after V
DD
is within tolerance to
allow the power supply and processor to stabilize.
FIGURE 3-1:
Watchdog Strobe
3.2
Watchdog Timer
The processor drives the RS pin with an input/output
(I/O) line in series with an resistor voltage divider to
V
DD.
Pulling the bottom resistor of this divider low
results in an internal voltage change (strobe) sufficient
to reset the Watchdog Timer, but above the V
IL
input
threshold of the processor Reset pin. The processor
must continuously apply strobes in this manner within
a set period to verify proper software execution. A
momentary Reset (500 msec minimum) is generated
by the TC32M if a hardware or software failure keeps
RS from being strobed within the Watchdog Time-out
period. This action typically initiates the processor’s
power-up routine. If the interruption persists, new
Reset pulses are generated each time-out period until
RS is strobed. This time-out period is typically 700
msec.
The software routine that drives the RS strobe must be
in a section of the program that executes frequently
enough so the time between toggles is less than one
Watchdog Time-out period. The strobe signal can be
derived from microprocessor address, data and/or
control signals. Typical circuit examples are shown in
Figure .
3.3
Resistor Value Selection
The values of R1 and R2 must be chosen to ensure a
valid low strobe level (V
STL
) on RS when the processor
I/O line is low. The use of 10 k, ±5% tolerance
resistors are recommended. These values result in a
nominal strobe level of 2.5 on RS (min/max of 2.13V/
3.08V, assuming V
DD
= 5.0V ±10%). Other resistor
values can be used, so long as the additive tolerances
of the power supply and resistor values result in a
strobe that falls within V
STH
and V
STL
under all additive
tolerance conditions.
2001-2012 Microchip Technology Inc.
DS21402D-page 5
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