Data sheet
AS1923
Q u a d - Vo l ta g e M i c r o p r o c e s s o r S u p e r v i s o r y C i r c u i t
1 General Description
The AS1923 microprocessor supervisory circuit was designed to
monitor up to four system supply voltages without the need for exter-
nal components, and asserts a single reset if any of the monitored
supply voltages drops below its reset threshold.
The AS1923 features an active-low reset output that is asserted
when any of the 4 monitored voltages are below their respective
reset threshold. The reset output is open-drain with a weak internal
pullup (10µA) to IN2. Reset remains low for a specified reset timeout
period (120ms min) after all voltages have stabilized. The output is
valid as long as the IN1 or IN2 input voltage remains >1V.
Minimal external component requirements, small size, and wide tem-
perature range (-40 to +85°C) greatly improves reliability compared
to individual supervisory circuits or discrete components.
A wide range of factory-trimmed threshold voltages are available to
accommodate many different supply voltages/tolerances with mini-
mal external component requirements.
Factory-trimmed options are available for monitoring +5.0, +3.3,
+3.0, +2.5, +1.8, and -5.0V supplies with -5% and/or -10% toler-
ances. The device is also available with one or two user-adjustable
threshold options (via external resistor-divider network) if non-stan-
dard voltage thresholds are required.
The AS1923 is available in an 6-pin SOT23 package.
2 Key Features
Simultaneous Quad-Voltage Monitoring
Precision Factory-Trimmed Reset Threshold Options: +5.0,
+3.3, +3.0, +2.5, +1.8, and -5.0V
User-Adjustable Voltage Monitoring Threshold Options
Low Supply Current: 55µA
Open-Drain – AS1923A
10µA Current Source Pullup – AS1923B
Reset Timeout Period: 120ms
RESET Valid to IN1 = 1V or IN2 = 1V
Immune to Fast INx Transients
External Components not Required
Guaranteed Performance: Operating Temperature Range = -40
to +85ºC
6-pin SOT23 Package
3 Applications
The device is ideal for portable and battery-powered systems,
embedded controllers, intelligent instruments, automotive systems,
critical CPU monitoring, and any multi-supply application.
Figure 1. AS1923 - Typical Application
Monitoring
Voltage 1
Monitoring
Voltage 2
Monitoring
Voltage 3
Monitoring
Voltage 4
4
IN1
5
IN2
6
IN3
1
IN4
GND
2
AS1923
3
RESETN
RESETN
CPU
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AS1923
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
IN4 1
6 IN3
GND 2
AS1923
5 IN2
RESETN 3
4 IN1
Pin Descriptions
Table 1. Pin Descriptions
Pin Number
1
2
3
4
5
6
Pin Name
IN4
GND
RESETN
IN1
IN2
IN3
Ground
Reset Output.
AS1923A
(see Ordering Information on page 14)
supports an external pullup resistor; AS1923B
contains an internal 10µA current source pullup. RESETN goes low (reset asserted) when any one of the INx
voltages goes below its specified threshold. After all inputs have stabilized, RESETN remains low for at least
120ms (min) before going high.
Input Voltage 1.
See Ordering Information on page 14
for monitored voltages.
Input Voltage 2.
See Ordering Information on page 14
for monitored voltages.
Note:
IN2 is the power supply input for the AS1923.
Input Voltage 3.
See Ordering Information on page 14
for monitored voltages.
Description
Input Voltage 4.
See Ordering Information on page 14
for monitored voltages.
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AS1923
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in
Table 2
may cause permanent damage to the device. These are stress ratings only, and functional operation of
the device at these or any other conditions beyond those indicated in
Electrical Characteristics on page 4
is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
Electrical Parameters
IN1, IN2 (Monitored Voltage), IN3, IN4 to GND
IN4 to GND (Device Variants M, N, O, and P, see
Table 5
on page 14)
RESETN to GND
Latchup immunity
Continuous Power Dissipation
Continuous Power Dissipation
(T
AMB
= +70ºC)
Temperature Ranges and Storage Conditions
Junction Temperature
Storage Temperature Range
-55
+150
+150
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC
J-STD-020 “Moisture/Reflow Sensitivity Classification for
Non-Hermetic Solid State Surface Mount Devices”.
The lead finish for Pb-free leaded packages is matte tin
(100% Sn).
Represents a max. floor life time of unlimited
696
mW
Derate 8.7mW/ºC above +70ºC
-0.3
-7
-0.3
+7
+0.3
+6
V
V
V
Class I Level A in accordance with
EIA/JEDEC 78
Min
Max
Units
Comments
Package Body Temperature
+260
ºC
Humidity non-condensing
Moisture Sensitive Level
5
1
85
%
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AS1923
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
IN2
= +1V to +5.5V, Typ values @ V
IN2
= +3.0V to +3.3V, T
AMB
= +25ºC (unless otherwise specified).
Table 3. Electrical Characteristics
Symbol
Tamb
V
IN2
Parameter
1
Conditions
2, 3
Min
-40
1.0
Typ
Max
85
5.5
Units
°C
V
Operating Temperature Range
Supply Voltage Range
V
INx
= Input Threshold Voltage (Input Threshold
Voltage of 1.8, 2.5, or 5V)
V
IN2
= Input Threshold Voltage (Input Threshold
4
Voltage of 3.0 or 3.3V)
I
INx
Input Current
V
INx
= 0 to V
IN2
5
(Input Threshold Voltage = +1.23V)
V
IN1
= 1.5V (AS1923 K/L only)
V
INx
= -5V (Input Threshold Voltage = -5V)
V
INx
Decreasing, +5V (-5%) Threshold
V
INx
Decreasing, +5V (-10%) Threshold
V
INx
Decreasing, +3.3V (-5%) Threshold
V
INx
Decreasing, +3.3V (-10%) Threshold
V
TH
Reset Threshold Voltage
V
INx
Decreasing, +3.0V (-5%) Threshold
V
INx
Decreasing, +3.0V (-10%) Threshold
V
INx
Decreasing, +2.5V (-10%) Threshold
V
INx
Decreasing, +1.8V (-10%) Threshold
V
INx
Increasing, -5V (+5%) Threshold
V
INx
Increasing, -5V (+10%) Threshold
V
TH
Adjustable Threshold
Threshold Voltage
Temperature Coefficient
V
HYS
t
RD
t
RP
Threshold Hysteresis
Reset Delay
Reset Active Timeout Period
V
INx
= V
TH
to (V
TH
- 50mV),
All Inputs Except -5V, or
V
INx
= V
TH
to (V
TH
+ 50mV), -5V Input Only
120
V
INx
Decreasing
4.50
4.25
3.00
2.85
2.70
2.55
2.13
1.53
-4.75
-4.50
1.20
-0.1
25
55
40
115
µA
0.1
0.4
-15
4.63
4.38
3.08
2.93
2.78
2.63
2.19
1.58
-4.63
-4.38
1.23
60
0.5
20
200
1.5
-20
4.75
4.50
3.15
3.00
2.85
2.70
2.25
1.62
-4.50
-4.25
1.26
V
ppm/ºC
%
µs
280
ms
V
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AS1923
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
Table 3. Electrical Characteristics (Continued)
Symbol
V
OL
Parameter
1
Conditions
V
IN2
= 5V, I
SINK
= 2mA
V
IN2
= 2.5V, I
SINK
= 1.2mA
V
IN1
= V
IN2
= 1V, I
SINK
= 50µA
V
IN2
> 2.55V, I
SOURCE
= 6µA
(Reset Not Asserted)
V
IN2
≥
2.55V (Reset Not Asserted),
V
OUT
≥
0.8 x V
IN2
Min
Typ
Max
0.4
0.4
0.4
Units
V
Output Low Voltage
Output High Voltage,
Output High Source Current
Output High Source Current
V
OH
I
OH
1.
2.
3.
4.
6
5
0.8 x
V
IN2
6
10
V
µA
100% production tested at T
AMB
= +25ºC. Limits over temperature guaranteed by design.
The device is powered from input IN2.
The RESETN output is guaranteed to be in the correct state for IN1 or IN2 down to 1V.
Monitored voltage at IN2 (+3.3V, +3.0V) is also the device power supply. Supply current split is 25µA for the resistor-divider network (for
the monitored voltage) and 30µA for other circuits.
5. Adjustable pin only.
6. AS1923B only.
Note:
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality
Control) methods.
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