MITSUMI
System Reset PST993, 994
System Reset
Monolithic IC PST993, 994
Outline
The function of this IC is to accurately reset systems after detecting the supply voltage at the time of
switching power on and instantaneous power off in various CPU and other logic systems. Further, this IC can
be offered at low cost because it is designed to be simplified allowing for the replacement from reset circuit of
discrete configuration.
Features
1. Voltage detect precision
V
S
5% max.
2. Low consumption current
I
CCH
=300A typ. I
CCL
=250A typ.
3. Low operating threshold voltage
0.65V typ.
4. Hysteresis voltage is provided as detect voltage
50mV typ.
5. Large output current at the time ON
15mA typ.
6. Detect voltage rank
PST993 C : 4.5V
H : 3.1V
D : 4.2V
I : 2.9V
E : 3.9V
J : 2.7V
F : 3.6V
K : 2.5V
G : 3.3V
L : 2.3V
(Same ranks for PST994 too)
7. Output form
PST993 : Constant current load built-in
PST994 : Open collector
Packages
TO-92A (PST993 , PST994 )
*
contains detection voltage rank.
Applications
1. Reset circuits for microcomputers, CPU and MPU.
2. Reset circuit for logic circuitry.
3. Level detecting circuit.
Pin Assignment
1
2
3
TO-92A
1
V
CC
2
GND
3
V
OUT
MITSUMI
System Reset PST993, 994
Absolute Maximum Ratings
(Ta=25
C)
Electrical Characteristics
(Ta=25
C) (The unit of resistance is
unless otherwise indicated.)
Equivalent Circuit Diagram
PST993
PST994
Item
Symbol
Ratings
Units
Storage temperature
T
STG
-40~+125
C
Operating temperature
T
OPR
-20~+75
C
Supply voltage
V
CC
-0.3~10
V
Allowable loss
Pd
300
mW
Item
Symbol
Measurement
Measurement conditions
Min. Typ. Max. Units
Circuit
PST993C
4.27
4.5
4.73
PST993D
4.00
4.2
4.40
PST993E
3.70
3.9
4.10
PST993F
3.42
3.6
3.78
Detection Voltage
V
S
1
R
L
=
PST993G
3.13
3.3
3.47
V
V
CC
=H L
PST993H
2.94
3.1
3.26
PST993I
2.75
2.9
3.05
PST993J
2.56
2.7
2.84
PST993K
2.37
2.5
2.63
PST993L
2.18
2.3
2.42
Hysteresis Voltage
V
S
1
R
L
=
, V
CC
=L H L
30
50
100
mV
Detection Voltage
Temperature Coefficient
V
S
/ T
1
R
L
=
, Ta=-20~+75
C
0.01
%/
C
Low Level Output Voltage
V
OL
1
V
CC
=Vs min. -0.05V, R
L
=1k
0.1
0.4
V
Output Constant Current
I
O
C
1
V
O
=2.5V, V
CC
=5V, R
L
=
-40
-25
-17
A
Circuit Current at ON Time
I
CCL
1
V
CC
=Vs min. -0.05V, R
L
=
250
400
A
Circuit Current at OFF Time
I
CCH
1
V
CC
=Vs typ. /0.85V, R
L
=
300
500
A
"H" Transmission Delay Time
tpLH
2
C
L
=100pF
20
*
1
S
"L" Transmission Delay Time
tpHL
2
C
L
=100pF
1
S
Operating Threshold Voltage
V
OP
L
1
R
L
=4.7k, V
OL
<
= 0.4V
0.65
0.85
V
Output Current at ON Time 1
I
O
L1
1
R
L
=
, V
O
=0.4V
V
CC
=V
S
min. -0.05V
6
15
mA
Output Current at ON Time 2
I
O
L2
1
Ta=-20~+75
C, R
L
=
V
O
=0.4V, V
CC
=Vs min. -0.05V
4
mA
*
Do not apply onto the OUT terminal any voltage higher than that at the V
CC
terminal.
(
*
1) The tpLH is a function of the charging time of C
L
by output constant current.
The delay time of this IC is about 1 S.
MITSUMI
System Reset PST993, 994
Absolute Maximum Ratings
(Ta=25
C)
Electrical Characteristics
(Ta=25
C) (The unit of resistance is
unless otherwise indicated.)
Item
Symbol
Ratings
Units
Storage temperature
T
STG
-40~+125
C
Operating temperature
T
OPR
-20~+75
C
Supply voltage
V
CC
-0.3~10
V
Allowable loss
Pd
300
mW
Item
Symbol
Measurement
Measurement conditions
Min. Typ. Max. Units
Circuit
PST994C
4.27
4.5
4.73
PST994D
4.00
4.2
4.40
PST994E
3.70
3.9
4.10
PST994F
3.42
3.6
3.78
Detection Voltage
Vs
1
R
L
=1k
PST994G
3.13
3.3
3.47
V
V
CC
=H L
PST994H
2.94
3.1
3.26
PST994I
2.75
2.9
3.05
PST994J
2.56
2.7
2.84
PST994K
2.37
2.5
2.63
PST994L
2.18
2.3
2.42
Hysteresis Voltage
Vs
1
R
L
=1k, V
CC
=L H L
30
50
100
mV
Detection Voltage
Temperature Coefficient
Vs/ T
1
R
L
=1k, Ta=-20~+75
C
0.01
%/
C
Low Level Output Voltage
V
OL
1
V
CC
=Vs min. -0.05V, R
L
=1k
0.1
0.4
V
Output Leakage Current
I
OH
1
V
CC
=10V
0.1
A
Circuit Current at ON Time
I
CCL
1
V
CC
=Vs min. -0.05V, R
L
=
250
400
A
Circuit Current at OFF Time
I
CCH
1
V
CC
=Vs typ./0.85V, R
L
=
300
500
A
"H" Transmission Delay Time
tpLH
2
C
L
=100pF, R
L
=4.7k
1
S
"L" Transmission Delay Time
tpHL
2
C
L
=100pF, R
L
=4.7k
1
S
Operating Threshold Voltage
V
OP
L
1
R
L
=4.7k, V
OL
<
= 0.4V
0.65
0.85
V
Output Current at ON Time 1
I
O
L1
1
V
O
=0.4V
V
CC
=Vs min. -0.05V
6
15
mA
Output Current at ON Time 2
I
O
L2
1
Ta=-20~+75
C
V
O
=0.4V, V
CC
=Vs min.-0.05V
4
mA
*
Do not apply onto the OUT terminal any voltage higher than that at the V
CC
terminal.
(
*
1) The tpLH is a function of the charging time of C
L
by output constant current.
The delay time of this IC is about 1 S.
MITSUMI
System Reset PST993, 994
-20-10 0
10 20 30 40 50 60 70
30
40
50
60
70
80
90
100
Ta (
C)
V
O
L
(mV)
-20-10 0
10 20 30 40 50 60 70
0
10
20
30
40
50
60
70
80
90
100
Ta (
C)
V
S
(mV)
V
S
vs. Ta
V
O
L vs. Ta
-20-10 0
10 20 30 40 50 60 70
160
200
240
280
320
360
400
440
Ta (
C)
I
CC
H
(
A)
PST994
PST993
I
CC
H vs. Ta
-
20
-
10 0
10 20 30 40 50 60 70
-40
-38
-36
-34
-32
-30
-28
-26
-24
-22
-20
Ta (
C)
I
O
C
(
A)
I
O
C vs. Ta (PST993)
-20-10 0
10 20 30 40 50 60 70
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Ta (
C)
VopL
(V)
-20-10 0
10 20 30 40 50 60 70
4100
4120
4140
4160
4180
4200
4220
4240
4260
4280
4300
Ta (
C)
V
S
(mV)
V
S
vs. Ta
V
O
pL vs. Ta
Characteristics
Equivalent Circuit Diagram
*
Since PST993 incorporates a constant current load, the pull-up resistance is not necessary.
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