2002 Fairchild Semiconductor Corporation
1
www.fairchildsemi.com
February 2003
FM1233D 3-Pin C Super
visor Cir
cuit
FM1233D Rev. D
FM1233D
3-Pin C Supervisor Circuit
General Description
The FM1233D is a supervisor circuit that monitors a micropro-
cessor power supply or other system voltage and issues a reset
pulse when a fault condition exists. Several different threshold
voltages are offered to accommodate 5V systems with different
tolerances.
The device features a precision temperature-compensated volt-
age reference and comparator. When V
CC
falls to the threshold
voltage, a RESET pulse is issued, holding the output in the
active state. When power rises above V
TH
, the reset remains for
approximately 250 ms to allow the system clock and other cir-
cuits to stabilize. The reset output of FM1233D is of open-drain
active low type.
Features
s
Precision monitoring of 5V and lower voltage microprocessor
systems
s
V
TH
values of 4.62V, 4.38V and 4.12V
s
Automatic restart of microprocessor after power failure
s
140ms (min) power-on RESET delay (typ.: 256ms)
s
Internal 5k
pull-up resistor
s
Other reset choices available: 32 to 128ms
s
Operating Temperature -40C to +105C
s
SOT23-3 package
Typical Operating Circuit
Connection Diagram
SOT23-3 Package
1
FM1233D
Controller
2
3
VCC
GND
RESET
GND
VCC
RESET
1
FM1233D
2
3
FM1233D 3-Pin C Super
visor Cir
cuit
2
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FM1233D Rev. D
Absolute Maximum Ratings
Voltage on any pin relative to GND
V
CC
-0.3V to +6.0V
RESET
-0.3V to (V
CC
+ 0.3V)
Input Current
20mA
Output Current (RESET)
20mA
ESD Rating:
Human Body Model
>2KV
Machine Model
>200KV
Continuous Power Dissipation (T
A
= 70C)
SOT23 (derate 4mW above 70C)
300mW
Operating Temperature Range
-40C to +105C
Storage Temperature Range
-65C to +150C
Lead Temperature (soldering, 10s)
+300C
These are stress ratings only, and functional operation is not implied for these levels or beyond. Exposure to Absolute Maximum
Rating conditions for extended periods may affect device reliability.
Electrical Characteristics (V
CC
= 5V; T
A
= -40C to +105C unless otherwise noted)
(Note 1)
Note 1:
Testing at production is done at 25C only. Limits over temperature are guaranteed by design.
Parameter
Symbol
Conditions
Min
Typ
Max
Units
Operating Voltage
V
CC
4.5
5
5.5
V
Supply Current
I
CC
V
CC
< 5V
3
6
A
Reset Threshold
V
TH
FM1233DF
4.40
4.63
4.86
V
Reset Threshold
V
TH
FM1233DD
4.16
4.38
4.55
V
Reset Threshold
V
TH
FM1233DE
3.91
4.12
4.32
V
Reset Output Voltage
V
OL
FM1233D
Isink = 5mA
V
CC
= V
TH
(min)
0.4
V
Reset Timeout Period
t
RST
FM1233D
140
256
560
ms
3
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FM1233D Rev. D
FM1233D 3-Pin C Super
visor Cir
cuit
Typical Operating Characteristics
Supply Current Vs. Temperature
Power up Reset Timeout Vs. Temperature
0
2
4
6
8
10
0
2
4
6
8
10
+110C
+25C
-55C
Temperature (C)
I
CC
(
A)
100
200
300
400
500
600
100
200
300
400
500
600
+105C
+25C
-40C
Temperature (C)
P
o
w
er up Reset timeout (ms)
FM1233D 3-Pin C Super
visor Cir
cuit
4
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FM1233D Rev. D
Pin Descriptions
Circuit Timing (Ex: FM1233D)
When operating properly with 5V V
CC
(for example), RESET will
also be about 5V. When V
CC
starts to fall, RESET will follow it
down as shown. When V
CC
drops below V
TH
, RESET drops to
ground ("issues a RESET") and stays there unless V
CC
also
falls below its minimum operating voltage, approx. 1V. At this
point, the supervisor loses control, and its output may rise, only
to again follow V
CC
down to the ground.
When V
CC
begins to rise, RESET follows it until 1.0V or so is
reached, whereupon the device regains control, RESET is
pulled to ground, etc. When V
CC
rises above V
TH
, RESET
comes out of RESET 140 ms later.
If it is required that a lower value than GND + 1.0V is needed
on RESET signal during V
CC
1V, a 100K resistor may be used
on the device output to GND.
Pin Number
Name
Function
1
GND
GROUND
2
RESET
RESET remains LOW while V
CC
is below V
TH
, and
for at least 140ms after V
CC
rises above V
TH
.
3
V
CC
5V
V
TH
1V
GND
5V
V
TH
1V
GND
V
CC
RESET
140ms
FM1233D 3-Pin C Super
visor Cir
cuit
5
www.fairchildsemi.com
FM1233D Rev. D
General Description
The FM1233D features a highly accurate voltage reference to
which V
CC
is compared. Once V
CC
is below the specified
threshold, it will drive the RESET line and continue to hold it low
until V
CC
returns above the threshold and the time for the
RESET pulse duration has expired. The FM1233D is immune to
short negative going transients on the V
CC
line. The placement
of a 0.1F bypass capacitor as close as possible to the V
CC
pin
provides additional transient immunity.
For a V
CC
value below 1.0V, the FM1233D does not sink very
much current on the RESET pin. This is not a problem in most
systems since common devices are not functional in this range.
If it is desired for the FM1233D reset to be functional below this
range, use a 100K
pull-down resistor between RESET and
V
SS
.
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