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
D a ta S he e t
1 General Description
The AS1923 microprocessor supervisory circuit was
designed to monitor up to four system supply voltages
without the need for external 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 out-
put is valid as long as the IN1 or IN2 input voltage
remains >1V.
Minimal external component requirements, small size,
and wide temperature 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 volt-
ages/tolerances with minimal 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% tolerances. The device is also available
with one or two user-adjustable threshold options (via
external resistor-divider network) if non-standard voltage
thresholds are required.
The AS1923 is available in an 6-pin SOT23 package.
2 Key Features
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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
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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. Application Diagram and Pinout
4
IN1
5
IN2
6
IN3
1
IN4
GND
2
RESETN 3
4 IN1
Monitoring
Voltage 1
Monitoring
Voltage 2
Monitoring
Voltage 3
Monitoring
Voltage 4
IN4 1
6 IN3
AS1923
3
RESETN
RESETN
CPU
GND 2
AS1923
5 IN2
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AS1923
Data Sheet - 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
Pin
Name
IN4
GND
Description
Input Voltage 4.
See Ordering Information on page 12
for monitored voltages.
Ground
3
Reset Output.
AS1923A
(see Ordering Information on page 12)
supports an external pullup
resistor; AS1923B contains an internal 10µA current source pullup. RESETN goes low
RESETN
(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.
IN1
IN2
IN3
Input Voltage 1.
See Ordering Information on page 12
for monitored voltages.
Input Voltage 2.
See Ordering Information on page 12
for monitored voltages.
Note:
IN2 is the power supply input for the AS1923.
Input Voltage 3.
See Ordering Information on page 12
for monitored voltages.
4
5
6
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AS1923
Data Sheet - 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 Character-
istics 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
IN1, IN2 (Monitored Voltage), IN3, IN4 to GND
IN4 to GND (Device Variants M, N, O, and P,
see
Table 5 on page 12)
RESETN to GND
Continuous Power Dissipation
(T
AMB
= +70ºC)
Latchup immunity
Operating Temperature Range
Storage Temperature Range
Junction Temperature
-40
-65
+85
+150
+150
ºC
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC J-STD-020C “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).
Min
-0.3
-7
-0.3
Max Units
+7
+0.3
+6
695
V
V
V
mW
Derate 8.7mW/ºC above +70ºC
Class I Level A in accordance with
EIA/JEDEC 78
Comments
Package Body Temperature
+260
ºC
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AS1923
Data Sheet - 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
= +1 to +5.5V, T
AMB
= -40 to +85ºC (unless otherwise specified). Typ values @ V
IN2
= +3.0 to +3.3V, T
AMB
=
+25ºC (unless otherwise specified).
Table 3. Electrical Characteristics
Symbol
V
IN2
Parameter
1
2, 3
Conditions
Min
1.0
Typ
Max
5.5
Units
V
Supply Voltage Range
V
INx
= Input Threshold Voltage (Input
Threshold Voltage of 1.8, 2.5, or 5V)
V
IN2
= Input Threshold Voltage (Input
4
Threshold 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
V
OL
Threshold Hysteresis
Reset Delay
Reset Active Timeout Period
V
IN2
= 5V, I
SINK
= 2mA
Output Low Voltage
Output High Voltage,
Output High Source Current
Output High Source Current
V
IN2
= 2.5V, I
SINK
= 1.2mA
V
IN1
= V
IN2
= 1V, I
SINK
= 50µA
V
OH
I
OH
6
5
25
55
-0.1
0.4
-15
4.50
4.25
3.00
2.85
2.70
2.55
2.13
1.53
-4.75
-4.50
1.20
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
40
115
µA
0.1
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
0.4
0.4
0.4
V
ms
V
V
INx
Decreasing
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
20
200
V
IN2
> 2.55V, I
SOURCE
= 6µA
(Reset Not Asserted)
V
IN2
≥
2.55V (Reset Not Asserted),
V
OUT
≥
0.8 x V
IN2
0.8 x
V
IN2
6
10
V
µA
1. 100% production tested at T
AMB
= +25ºC. Limits over temperature guaranteed by design.
2. The device is powered from input IN2.
3. The RESETN output is guaranteed to be in the correct state for IN1 or IN2 down to 1V.
4. 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.
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AS1923
Data Sheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
Tamb
= +25ºC, unless otherwise noted
Figure 3. IN2 Input Current vs. IN2 Input Voltage
85
Figure 4. IN2 Input Current vs. Temperature
70
IN2 Input Current (mA)
.
IN2 Input Current (mA)
.
80
75
70
65
60
55
3
3.5
4
4.5
5
5.5
65
V
IN2 =
3.3V
60
V
IN2 =
3.0V
55
50
-40
-20
0
20
40
60
80
IN2 Input Voltage (V)
Temperature(°C)
Figure 5. Reset Delay vs. Reset Threshold Overdrive;
V
IN2
= 3.0V, IN decreasing
80
Figure 6. Reset Timeout Periode vs. Temperature;
V
IN2
= 3.0V, IN decreasing
225
.
60
Reset Timeout Periode (ms)
0
200
400
600
800
1000
220
215
210
205
200
195
-40
Reset Delay (µs)
.
40
20
0
-15
10
35
60
85
Reset Threshold Overdrive (mV)
Temperature (°C)
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