A S 1 9 0 1 , A S 1 9 0 2 , A S 1 9 0 3
U l t r a L o w - P o w e r P S u p e r v i s o r y C i r c u i t
austria
micro
systems
D a t a S h e e t
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1 General Description
The AS1901/2/3 family is an ultra low-power supervisory
circuit device.
The device can be used to monitor the supply voltage of
digital systems and microprocessors and initiate a reset
when the voltage goes below a predefined threshold.
The duration of the reset is 5/20/100/500ms (typ.) after
the supply voltage has risen above the threshold.
The AS1901/2/3 exhibit excellent reliability and can
reduce application costs by eliminating all external com-
ponents.
The device is available with different output drivers:
The AS1901 has a push-pull driver with an active low
reset.
The AS1902 uses the same output stage as the
AS1901, but has an active high reset.
The AS1903 has an open drain output with active low
reset.
All devices operate down to a voltage of 1V.
The reset thresholds are factory-trimmable between
2.2V and 3.08V in steps of approximately 100mV.
Each device of the AS1901/2/3 family is offered with four
time-out periods of 5/20/100/500ms.
The extremely low current consumption of only 230nA
(typ) at 3.3V makes the device ideal for use in portable
applications.
All devices are available in a 3-pin SOT23 package.
Figure 1. Functional Block Diagrams
2 Key Features
Low 230nA (typ) Supply Current
Precision Monitoring of 2.5-, 3-, and 3.3V-Power
Supplies
Supply Voltage Range: 1.0 to 3.6V
Reset Threshold Range: 2.2 to 3.1V
Available in 3 Versions:
- AS1901 Push Pull RESETN
- AS1902 Push Pull RESET
- AS1903 Open Drain RESETN
4 Time-Out Periods Ranging from 5 to 500ms
Detection Voltage Accuracy: 1.5%
Temperature Range: -40 to +85C
Package: SOT23-3
Pin Compatible to MAX6326/6327/6328
3 Applications
Computers
Intelligent Instruments
Controllers
Critical Microprocessor and Microcontroller
Power Monitoring
Portable/Battery-Powered Equipment
Automotive
V
CC
AS1903
Microprocessor
V
DD
GND
GND
RESETN
RESET I/O
V
CC
1
2
3
V
CC
AS1901
AS1902
Microprocessor
V
DD
GND
GND
RESETN,
RESET
RESET
V
CC
1
2
3
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Data Sheet
4 Absolute Maximum Ratings
Stresses beyond those listed in Table 1 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 Section 5 Electrical
Characteristics is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Table 1. Absolute Maximum Ratings
(
T
A
= 25C Unless Otherwise Noted)
Parameter
Limits
Unit
Notes
V
DD
to GND
-0.3 to +5
V
RESET/RESETN to GND
-0.3 to V
DD
+ 0.3
V
Input Current (V
DD
) 20
mA
Output Current (RESET, RESETN)
20
mA
Rate of Rise (V
DD
) 100
V/s
Operating Temperature Range (T
A
)
-40 to +85
C
Storage Temperature Range
-65 to +150
C
Package-Body Peak Temperature
+260
C
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"
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Data Sheet
5 Electrical Characteristics
V
DD
= Full Range; T
A
= -40 to +85C; Unless Otherwise Specified
Notes:
1
See Table 5, "Coding of Factory-Trimmed Reset Threshold Voltages," on page 5.
2
Guaranteed by design.
3
See Table 3, "Coding of Factory-trimmed Reset Active Time-Out Period," on page 5.
Table 2. Electrical Characteristics
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
V
DD
Range
V
DD
T
A
= 0 to +70C
1.0
3.6
V
T
A
= -40 to +85C
1.2
3.6
Supply Current (AS1901/2/3)
I
DD
V
DD
= 3.3V, No Load
230
430
nA
Reset Threshold Voltage
1
V
TH
T
A
= +25C
V
TH
-
1.5%
V
TH
V
TH
+
1.5%
V
T
A
= -40 to +85C
V
TH
-
2.5%
V
TH
V
TH
+
2.5%
V
DD
to Reset Delay
2
t
RD
V
DD
= V
TH
to (V
TH
- 100mV)
20
50
s
Reset Active Time-Out Period
3
t
TP
t
TP
-
40%
t
TP
t
TP
+
60%
ms
RESETN Output Voltage (AS1901/3)
V
OL
I
SINK
= 1.2mA, V
DD
= 2.1V, Reset
Asserted
0.4
V
I
SINK
= 400A, V
DD
= 1.2V, Reset
Asserted
0.4
V
RESETN Output Voltage (AS1901)
V
OH
I
SOURCE
= 1.2mA, V
DD
= 3.2V
0.8 x
V
DD
V
RESET Output Voltage (AS1902)
V
OH
I
SOURCE
= 500A, V
DD
= 2.1V,
Reset Asserted
0.8 x
V
DD
V
I
SOURCE
= 100A, V
DD
= 1.2V,
Reset Asserted
0.8 x
V
DD
V
V
OL
I
SINK
= 1.2mA, V
DD
= 3.2V,
Reset Not Asserted
0.4
V
RESET Threshold Hysteresis
V
HYST
10
mV
Open-Drain RESETN Output
Leakage Current (AS1903)
I
LEAK
0.1
A
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Data Sheet
Interfacing to Microprocessors with Bi-Directional Reset Pins
6 Operation
6.1 Interfacing to Microprocessors with Bi-Directional Reset Pins
The device has an open drain RESETN output, which enables easy interfacing to microprocessors (P) with bi-direc-
tional reset pins, such as the Motorola 68HC11. The RESETN pin of the microcontroller (C) can be connected directly
to the P supervisor's RESETN output with a single pull-up resistor (see Figure 1 on page 1).
6.2 Operating Characteristics
6.3 Negative-Going V
DD
Transients
The device is optimized to ignore short-duration, negative-going V
DD
transients (glitches) in order to avoid incorrect
resets.
In the graph Maximum Transient Duration vs. Reset Threshold Overdrive (page 4), the conditions are shown, for which
the reset pulses are not generated. In the graph the maximum pulse width that a negative V
DD
transient may have
when a reset signal is generated. As the amplitude of the transient increases, the maximum allowable pulse width
decreases.
Supply Current vs. Tem perature,
VCC=3.3V
0
0.1
0.2
0.3
0.4
0.5
-40
- 20
0
20
40
60
80
Temperature (C)
Supply Current (
A)
Pow er-Dow n Reset Delay
vs. Tem perature, VOD = 10m V
0
50
100
150
200
-40
-20
0
20
40
60
80
Temperature (C)
RESET DELAY (
s)
Power-Up Reset Timeout
vs. Temperature
0
40
80
120
160
200
-40
-20
0
20
40
60
80
Temperature (C)
Power Up Reset Timeout
(ms)
Maximum Transient Duration
vs. Reset Threshold Overdrive
0
100
200
300
400
1
10
100
1000
Reset Threshold Overdrive
Vth-Vcc (mV)
Maximum Transient Duration (
s)
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Data Sheet
7 Options
Table 3. Coding of Factory-trimmed Reset Active Time-Out Period
Device
Suffix
t
TP
in Milliseconds
Min
Typ
Max
AS190x_xx
A
3
5
8
AS190x_xx
B
12
20
32
AS190x_xx
C
60
100
160
AS190x_xx
D
300
500
800
Table 4. Output Variants
Device
Output Functionality
AS1901xxx
Active Low (RESETN)
AS1902xxx
Active High (RESET)
AS1903xxx
Open Drain (RESETN)
Table 5. Coding of Factory-Trimmed Reset Threshold Voltages
Device
Suffix
Reset Threshold Voltage, V
TH
in V
T
A
= +25C
T
A
= -40 to +85C
Min
Typ
Max
Min
Max
AS190xx__
22
2.167
2.2
2.233
2.145
2.255
AS190xx__
23
2.285
2.32
2.355
2.262
2.378
AS190xx__
24
2.364
2.4
2.436
2.340
2.460
AS190xx__
25
2.463
2.5
2.538
2.438
2.563
AS190xx__
26
2.591
2.63
2.669
2.564
2.696
AS190xx__
27
2.660
2.7
2.741
2.633
2.768
AS190xx__
28
2.758
2.8
2.842
2.730
2.870
AS190xx__
29
2.886
2.93
2.974
2.857
3.003
AS190xx__
30
2.955
3.0
3.045
2.925
3.075
AS190xx__
31
3.034
3.08
3.126
3.003
3.157
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austria
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Data Sheet
Pin Assignments
8 Pinout and Packaging
8.1 Pin Assignments
Figure 2. Pin Assignments (Top View)
8.2 Pin Descriptions
Table 6. Pin Descriptions
Pin Number
Pin Name
Description
AS1901/AS1903
AS1902
1
1
GND
Ground
2
-
RESETN
Active-low reset output. RESETN remains low while V
DD
is
below the reset threshold and for t
TP
after V
DD
rises above
the reset threshold. RESETN is open-drain on the AS1903
and push-pull on the AS1901.
-
2
RESET
Active-high reset output. RESET remains high while V
DD
is
below the reset threshold and for t
TP
after V
DD
rises above
the reset threshold.
3
3
V
DD
Supply voltage.
3
1
2
Top View
AS1901
AS1902
AS1903
SOT23-3
V
DD
GND
RESETN,
RESET
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Data Sheet
Package Drawings and Markings
8.3 Package Drawings and Markings
The device is available in a 3-pin SOT-23 package.
Figure 3. 3-Pin SOT-23 Package.
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Data Sheet
9 Ordering Information
The device is available in the following standard versions.
Non-standard versions require a minimum order of 30,000 units. Contact austriamicrosystems for availability of non-
standard versions.
Standard Part
Threshold
Duration
Marking
AS1901C23
2.32
100ms
ASBA
AS1901C26
2.63
100ms
ASBD
AS1901C31
3.08
100ms
ASBI
AS1902C23
2.32
100ms
ASBK
AS1902C26
2.63
100ms
ASBN
AS1902C31
3.08
100ms
ASBS
AS1903C23
2.32
100ms
ASBU
AS1903C26
2.63
100ms
ASBX
AS1903C31
3.08
100ms
ASB3
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AS1901, AS1902, AS1903
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Data Sheet
Copyrights
Copyright 1997-2005, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe.
Trademarks Registered . All rights reserved. The material herein may not be reproduced, adapted, merged, trans-
lated, stored, or used without the prior written consent of the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing
in its Term of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding
the information set forth herein or regarding the freedom of the described devices from patent infringement. austriami-
crosystems AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior
to designing this product into a system, it is necessary to check with austriamicrosystems AG for current information.
This product is intended for use in normal commercial applications. Applications requiring extended temperature
range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-
sustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for
each application.
The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However,
austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to
personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or
consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the tech-
nical data herein. No obligation or liability to recipient or any third party shall arise or flow out of
austriamicrosystems AG rendering of technical or other services.
Contact Information
Headquarters
austriamicrosystems AG
A-8141 Schloss Premstaetten, Austria
Tel: +43 (0) 3136 500 0
Fax: +43 (0) 3136 525 01
e-mail:
info@austriamicrosystems.com
For Sales Offices, Distributors and Representatives, please visit:
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