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austriamicrosystems
AS1901, AS1902, AS1903
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
D a ta S he e t
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 components. The device is available with different output drivers:
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

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.

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
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.
3 Applications

Computers Intelligent Instruments Controllers Critical Microprocessor and Microcontroller Power Monitoring Portable/Battery-Powered Equipment Automotive

Figure 1. Functional Block Diagrams
VCC 3 VDD VCC VCC 3 VDD VCC
AS1901 AS1902
RESETN, RESET GND 1 2
Microprocessor
AS1903
2
Microprocessor
RESET
RESETN
RESET I/O
GND
GND 1
GND
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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 (TA = 25C Unless Otherwise Noted) Parameter Limits Unit VDD to GND RESET/RESETN to GND Input Current (VDD) Output Current (RESET, RESETN) Rate of Rise (VDD) Operating Temperature Range (TA) Storage Temperature Range -0.3 to +5 -0.3 to VDD + 0.3 20 20 100 -40 to +85 -65 to +150 V V mA mA V/s C 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" Notes
Package-Body Peak Temperature
+260
C
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5 Electrical Characteristics
VDD = Full Range; TA = -40 to +85C; Unless Otherwise Specified Table 2. Electrical Characteristics Parameter VDD Range Supply Current (AS1901/2/3) Reset Threshold Voltage1 VDD to Reset Delay2 Reset Active Time-Out Period3 Symbol VDD IDD VTH TA = -40 to +85C tRD tTP ISINK = 1.2mA, VDD = 2.1V, Reset Asserted ISINK = 400A, VDD = 1.2V, Reset Asserted ISOURCE = 1.2mA, VDD = 3.2V ISOURCE = 500A, VDD = 2.1V, Reset Asserted ISOURCE = 100A, VDD = 1.2V, Reset Asserted ISINK = 1.2mA, VDD = 3.2V, Reset Not Asserted 10 0.1 0.8 x VDD 0.8 x VDD 0.8 x VDD 0.4 VDD = VTH to (VTH - 100mV) tTP 40% Conditions TA = 0 to +70C TA = -40 to +85C VDD = 3.3V, No Load TA = +25C VTH 1.5% VTH 2.5% Min 1.0 1.2 230 VTH VTH 20 tTP Typ Max 3.6 3.6 430 VTH + 1.5% VTH + 2.5% 50 tTP + 60% 0.4 0.4 Unit V nA V
s ms V V V V V V mV A
RESETN Output Voltage (AS1901/3)
VOL
RESETN Output Voltage (AS1901)
VOH
VOH RESET Output Voltage (AS1902) VOL RESET Threshold Hysteresis Open-Drain RESETN Output Leakage Current (AS1903) Notes:
1 2
VHYST ILEAK
See Table 5, "Coding of Factory-Trimmed Reset Threshold Voltages," on page 5. Guaranteed by design. Table 3, "Coding of Factory-trimmed Reset Active Time-Out Period," on page 5.
3 See
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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-directional 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
Supply Current vs. Tem perature, VCC=3.3V
0.5
200
Pow er-Dow n Reset Delay vs. Tem perature, VOD = 10m V
0.4
Supply Current (A)
RESET DELAY (s)
- 20 0 20 40 60 80
150
0.3
0.2
100
0.1
50
0 -40
0 -40 -20 0 20 40 60 80
Temperature (C)
Temperature (C)
Power-Up Reset Timeout vs. Temperature
200
Maximum Transient Duration vs. Reset Threshold Overdrive
400
Power Up Reset Timeout (ms)
Maximum Transient Duration (s)
160
300
120
200
80
100
40
0 -40 -20 0 20 40 60 80
0 1 10 100 1000
Temperature (C)
Reset Threshold Overdrive Vth-Vcc (mV)
6.3 Negative-Going VDD Transients
The device is optimized to ignore short-duration, negative-going VDD 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 VDD transient may have when a reset signal is generated. As the amplitude of the transient increases, the maximum allowable pulse width decreases.
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7 Options
Table 3. Coding of Factory-trimmed Reset Active Time-Out Period
Device
AS190x_xx AS190x_xx AS190x_xx AS190x_xx Table 4. Output Variants
Suffix
A B C D
tTP in Milliseconds Min
3 12 60 300
Typ
5 20 100 500
Max
8 32 160 800
Device
AS1901xxx AS1902xxx AS1903xxx
Output Functionality
Active Low (RESETN) Active High (RESET) Open Drain (RESETN)
Table 5. Coding of Factory-Trimmed Reset Threshold Voltages
Reset Threshold Voltage, VTH in V Device
AS190xx__ AS190xx__ AS190xx__ AS190xx__ AS190xx__ AS190xx__ AS190xx__ AS190xx__ AS190xx__ AS190xx__
Suffix Min
22 23 24 25 26 27 28 29 30 31 2.167 2.285 2.364 2.463 2.591 2.660 2.758 2.886 2.955 3.034
TA = +25C Typ
2.2 2.32 2.4 2.5 2.63 2.7 2.8 2.93 3.0 3.08
TA = -40 to +85C Max
2.233 2.355 2.436 2.538 2.669 2.741 2.842 2.974 3.045 3.126
Min
2.145 2.262 2.340 2.438 2.564 2.633 2.730 2.857 2.925 3.003
Max
2.255 2.378 2.460 2.563 2.696 2.768 2.870 3.003 3.075 3.157
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Pin Assignments
8 Pinout and Packaging
8.1 Pin Assignments
Figure 2. Pin Assignments (Top View)
Top View
GND
1
AS1901 AS1902 AS1903
3
VDD
RESETN, RESET
2
SOT23-3
8.2 Pin Descriptions
Table 6. Pin Descriptions
Pin Number AS1901/AS1903
1 2
AS1902
1 -
Pin Name
GND RESETN
Description
Ground Active-low reset output. RESETN remains low while VDD is below the reset threshold and for tTP after VDD rises above the reset threshold. RESETN is open-drain on the AS1903 and push-pull on the AS1901. Active-high reset output. RESET remains high while VDD is below the reset threshold and for tTP after VDD rises above the reset threshold. Supply voltage.
3
2 3
RESET VDD
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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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9 Ordering Information
The device is available in the following standard versions.
Standard Part
AS1901C23 AS1901C26 AS1901C31 AS1902C23 AS1902C26 AS1902C31 AS1903C23 AS1903C26 AS1903C31
Threshold
2.32 2.63 3.08 2.32 2.63 3.08 2.32 2.63 3.08
Duration
100ms 100ms 100ms 100ms 100ms 100ms 100ms 100ms 100ms
Marking
ASBA ASBD ASBI ASBK ASBN ASBS ASBU ASBX ASB3
Non-standard versions require a minimum order of 30,000 units. Contact austriamicrosystems for availability of nonstandard versions.
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Copyrights
Copyright (c) 1997-2005, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered (R). All rights reserved. The material herein may not be reproduced, adapted, merged, translated, 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. austriamicrosystems 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 lifesustaining 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 technical 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: http://www.austriamicrosystems.com
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