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FM1233D 3-Pin µC Supervisor Circuit
February 2003
FM1233D
3-Pin µC 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
s
s
s
Internal 5k
Ω
pull-up resistor
Other reset choices available: 32 to 128ms
Operating Temperature -40°C to +105°C
SOT23-3 package
Typical Operating Circuit
VCC
3
FM1233D
Controller
1
GND
2
RESET
Connection Diagram
GND
1
FM1233D
3
VCC
RESET
2
SOT23-3 Package
©2002 Fairchild Semiconductor Corporation
1
www.fairchildsemi.com
FM1233D Rev. D
FM1233D 3-Pin µC Supervisor Circuit
Absolute Maximum Ratings
Voltage on any pin relative to GND
V
CC
RESET
Input Current
Output Current (RESET)
-0.3V to +6.0V
-0.3V to (V
CC
+ 0.3V)
20mA
20mA
ESD Rating:
Human Body Model
Machine Model
Continuous Power Dissipation (T
A
= 70°C)
SOT23 (derate 4mW above 70°C)
Operating Temperature Range
>2KV
>200KV
300mW
-40°C to +105°C
Storage Temperature Range
-65°C to +150°C
Lead Temperature (soldering, 10s)
+300°C
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
= -40°C to +105°C unless otherwise noted)
(Note 1)
Parameter
Operating Voltage
Supply Current
Reset Threshold
Reset Threshold
Reset Threshold
Reset Output Voltage
Reset Timeout Period
Symbol
V
CC
I
CC
V
TH
V
TH
V
TH
V
OL
t
RST
V
CC
< 5V
FM1233DF
Conditions
Min
4.5
Typ
5
3
Max
5.5
6
4.86
4.55
4.32
0.4
Units
V
µA
V
V
V
V
ms
4.40
4.16
3.91
Isink = 5mA
V
CC
= V
TH
(min)
140
4.63
4.38
4.12
FM1233DD
FM1233DE
FM1233D
FM1233D
256
560
Note 1:
Testing at production is done at 25°C only. Limits over temperature are guaranteed by design.
2
FM1233D Rev. D
www.fairchildsemi.com
FM1233D 3-Pin µC Supervisor Circuit
Typical Operating Characteristics
Supply Current Vs. Temperature
10
8
10
8
6
4
2
-55C
+25C
+110C
0
I
CC
(µA)
6
4
2
0
Temperature (C)
Power up Reset Timeout Vs. Temperature
Power up Reset timeout (ms)
600
500
400
300
200
100
-40C
+25C
+105C
600
500
400
300
200
100
Temperature (C)
3
FM1233D Rev. D
www.fairchildsemi.com
FM1233D 3-Pin µC Supervisor Circuit
Pin Descriptions
Pin Number
1
2
3
Name
GND
RESET
V
CC
GROUND
Function
RESET remains LOW while V
CC
is below V
TH
, and
for at least 140ms after V
CC
rises above V
TH
.
Circuit Timing (Ex: FM1233D)
V
CC
5V
V
TH
1V
GND
RESET
5V
V
TH
1V
GND
140ms
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.
4
FM1233D Rev. D
www.fairchildsemi.com
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