ASM161 / ASM162
Alliance Semiconductor
2575 Augustine Drive . Santa Clara, CA 95054 . Tel: 408.855.4900 . Fax: 408.855.4999 . www.alsc.com
Notice: The information in this document is subject to change without notice
rev 1.0 µP Supervisory Circuit
October 2003
General Description
The ASM161 and ASM162 are cost effective, low power
supervisory circuits that monitor power supplies in
microprocessor, microcontroller and digital systems. If the
power supply drops below the reset threshold level, a reset is
asserted and remains asserted for atleast 800ms after VCC has
risen above the reset threshold. An improved manual reset
architecture gives the system designer additional flexibility.
The debounced manual reset input is negative edge triggered.
The reset pulse period generated by a MR transition is a
minimum of 800 ms and a maximum of 2 sec duration. In
addition, The MR input signal is blocked for an additional 49µS
minimum after the reset pulse ends. During the MR disable
period, the microcontroller is guaranteed a time period free of
additional manual reset signals. During this period DRAM
contents can be refreshed or other critical system tasks
undertaken. Low power consumption makes the ASM161/162
ideal for use in portable and battery operated equipments. With
3V supplies power consumption is 8µW typically and 30µW
maximum. The ASM161 has an open-drain, active-LOW
RESET output and requires an external pull-up resistor. The
ASM162 has an active HIGH RESET output.
The ASM161/162 are offered in compact 4-pin SOT-143
packages. No external components are required to trim
threshold voltage for monitoring different supply voltages. With
six different factory set, reset, threshold ranges from 2.63V to
4.63V, the ASM161/162 are suitable for monitoring 5V, 3.6V
and 3.0V supplies. The ASM161/162 are available in
temperature ranges 00 to 700c and -400c to +850c.
Key Features
• Edge triggered manual reset input
• single pulse output
• 49µS minimum MR disable period after reset
• CMOS/TTL logic or switch interface
• Debounced input
• Low supply current extends battery life
• 6µA / 15µA typ/max at 5.5V
• 4.5µA / 10µA typ/max at 3.6V
• Long reset period
• 0.8 sec minimum, 2 sec maximum
• Two reset polarity options
• ASM161: Active LOW, open-drain
• ASM162: Active HIGH
• Pinout matches the AS811/812
• Small 4-Pin SOT-143 package
• Two temperature ranges: 00 to 700c and -400c to +850c
Applications
•PDAs
• Appliances
• Computers and embedded controllers
• Wireless communication systems
• Battery operated and intelligent instruments
• Automotive systems
• Safety systems
Typical Operating Circuit
Reset Threshold
Part Suffix Voltage (V)
L4.63
M4.38
J4.00
T3.08
S2.93
R2.63
V
CC
MR
(RESET)
GND
(RESET)
µP
ASM161
(ASM162)
RESET RESET
V
CC
GND
V
CC
20k for
ASM161
only
ASM161 / ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
rev 1.0
October 2003
Block Diagram
Pin Configuration
RESET is open drain
Pin Description
Pin #
Pin Name Description
ASM161 ASM162
1 1 GND Ground.
2 - RESET
Active-LOW, open-drain reset output. RESET remains LOW while VCC is below the
reset threshold and for 800ms minimum after VCC rises above the reset threshold.
An external pull-up resistor is needed.
- 2 RESET Active HIGH reset output. RESET remains HIGH while VCC is below the reset
threshold and for 800ms after VCC rises above the reset threshold.
33MR
Manual reset input. A negative going edge transition on MR asserts reset. Reset
remains asserted for one reset time-out period (800 ms min). This active-LOW
input has an internal pull-up resistor. It can be driven from a TTL or CMOS logic line
or shorted to ground with a switch. Leave open if unused.
44
VCC Power supply input voltage.
+
-
Voltage
Divider
MR
Debounce
Bandgap
Reference
Reset Circuit
* Edge Trigger RESET (ASM162)
RESET (ASM161)
V
CC
MR
GND
1
2
3
4
ASM161/162
* Non-retriggerable, edge
triggered manual reset
~
~
~
~
Reset
Circuit
ASM161
V
CC
R
PU
2
4
1
23
4
GND
RESET MR
VCC
SOT-143
ASM161
1
23
4
GND
RESET MR
VCC
SOT-143
ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
ASM161 / ASM162
rev 1.0
October 2003
Detailed Descriptions
The reset function ensures the microprocessor is properly
reset and powers up into a known condition after a power
failure.
Reset Timing
A reset is generated whenever the supply voltage is below
the threshold level (VCC < VTH). The reset duration is at least
800ms after VCC has risen above the reset threshold and is
guaranteed to be no more than 2 seconds. The rest signal
remains active as long as the monitored supply voltage is
below the internal threshold voltage.
The ASM161 has an open-drain, active LOW RESET output
(which is guaranteed to be in the correct state for VCC down
to 1.1 V). The ASM161 uses an external pull-up resistor.
Output leakage current is under 1µA. A high resistance value
can be used to minimize current drain.
The ASM162 generates an active-HIGH RESET output.
Manual Reset
The ASM161/162 have a unique manual reset circuit. A
negative going edge transition on MR initiates the reset. A
manual reset generates a single reset pulse of fixed length.
The output-reset pulse remains asserted for the Reset Active
Time-Out Period tRP and then clears. Once the reset pulse is
completed, the MR input remains disabled for at least 49µS
but not more than 122µS. This period is specified as tMRD.
During the MR disabled period, the microcontroller is
guaranteed a time period free of new manual reset signals.
This period can be used to refresh critical DRAM contents or
other system tasks.
The MR pin must be taken HIGH and LOW again after the
tMRD period has been completed to initiate another reset
pulse.
The manual reset input has an internal 20kΩ pull-up resistor.
MR can be left open if not used.
Application Information
Glitch Resistance
The ASM161/162 are relatively immune to short duration
negative-going VCC transients/glitches. A VCC transient that
goes 100mV below the reset threshold and lasts 20s or less
will not typically cause a reset pulse.
Valid Reset with VCC under 1.1V
To ensure that logic inputs connected to the ASM162 RESET
pin are in a known state when VCC is under 1.1V, a 100kΩ
pull-down resistor at RESET is needed. The value is not
critical.
This scheme does not work with the open-drain outputs of
ASM161.
Part Number Reset Polarity
ASM161 LOW (use external pull-up resistor)
ASM162 HIGH
MR input is blocked
Ready
Reset
*Second and following edges ignored
*........
next
Triggering
tMD
tMRD
Figure 1: Manual Reset Timing
Time-Out
Pulse
for
MR
RESET
MR
V
CC
Power Supply
ASM162
RESET
GND
MR
Figure 2:
RESET valid with VCC under 1.1V
100K
Ω
ASM161 / ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
rev 1.0
October 2003
Absolute Maximum Ratings
Parameter Min Max Unit
Pin Terminal Voltage with respect to Ground
VCC -0.3 6.0 V
RESET, RESET and MR -0.3 VCC + 0.3 V
Input Current at VCC and MR 20 mA
Rate of Rise at VCC 100 V/µs
Power Dissipation (TA = 70°C) 320 mW
Operating Temperature Range -40 85 °C
Storage Temperature Range -65 160 °C
Lead Temperature (soldering, 10 sec) 300 °C
Note: These are stress ratings only and functional operation is not implied. Exposure to absolute maximum rat-
ings for prolonged time periods may affect device reliability.
ASM161 / ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
rev 1.0
October 2003
Electrical Characteristics
Unless otherwise noted, VCC is over the full range and TA = 00 to 700c for ASM161/162 X C and TA = -400c to +850c for ASM161/
162 X E devices. Typical values at TA = 250c, VCC = 5V for L/M/J devices, VCC = 3.3V for T/S devices and VCC = 3V for R devices
Parameter Symbol Conditions Min Typ Max Unit
Input Voltage (VCC)
Range
VCC TA = 0°C to 70°C 1.1 5.5 V
Supply Current
(Unloaded) ICC
TA = 0°C to 70°C,
TA = -40°C to +85°C
VCC < 5.5V,
L/M/J
615
µA
TA = 0°C to 70°C,
TA = -40°C to +85°C
VCC > 3.6V,
R/S/T
4.5 10
Reset Threshold VTH
L Devices TA = 25°C 4.56 4.63 4.70
V
Note 1 4.50 4.75
M devices TA = 25°C 4.31 4.38 4.45
Note 1 4.25 4.50
J devices TA = 25°C 3.93 4.00 4.06
Note 1 3.89 4.10
T devices TA = 25°C 3.04 3.08 3.11
Note 1 3.00 3.15
S devices TA = 25°C 2.89 2.93 2.96
Note 1 2.85 3.00
R devices TA = 25°C 2.59 2.63 2.66
Note 1 2.55 2.70
Reset Threshold Temp
Coefficient TCVTH 30 ppm/
°C
VCC to reset delay VCC = VTH to (VTH -100mV) 20 µS
Reset Pulse Width tRPW
TA = 0°C to 70°C 800 1400 2000
ms
TA = -40°C to 85°C 560 2240
MR Minimum Pulse
Width tMR 10 µS
MR Glitch Immunity 100 ns
MR to RESET Propaga-
tion Delay tMD 0.5 µs
ASM161 / ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
rev 1.0
October 2003
Notes: 1. Over operating temperature range.
MR Input Threshold
VIH VCC > VTH(MAX), L/M/J devices
2.3 V
VIL 0.8 V
VIH
VCC > VTH(MAX), R/S/T devices
0.7VCC V
VIL 0.25VCC V
MR Delay to MR Retrig-
ger tMRD
TA = 0°C to 70°C 49 85 122
µS
TA = -40°C to 85°C 85
MR pull-up resistance 10 20 30 KΩ
Low RESET output volt-
age (ASM161) VOL
VCC = VTH min., ISINK = 1.2mA,
ASM161 R/S/T
0.3
V
VCC = VTH min., ISINK = 3.2mA,
ASM161 L/M/J
0.4
VCC > 1.1, ISINK = 50µA 0.3
RESET Output Leak-
age Current (ASM161) ILKG VDRAIN < 6.0V, 0°C < TA < 70°C 1µA
Low RESET output volt-
age (ASM162) VOL
VCC = VTH min., ISINK = 1.2mA,
ASM162 R/S/T
0.3
V
VCC = VTH min., ISINK = 3.2mA,
ASM162 L/M/J
0.4
HIGH RESET Output
Voltage (ASM162) VOH 1.8<VCC<VTHmin., ISOURCE = 150 µA 0.8VCC V
Parameter Symbol Conditions Min Typ Max Unit
ASM161 / ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
rev 1.0
October 2003
Package Dimensions
Plastic SOT - 143 (4Pin)
EH
e
D
A
A1 eC
L
a = 0° -8°
B
e1
B1
Plastic SOT - 143 (4 pin)
Inches Millimeters
Min Max Min Max
Plastic SOT-143 (4-Pin)
A 0.031 0.047 0.787 1.194
A1 0.001 0.005 0.025 0.127
B 0.014 0.022 0.356 0.559
B1 0.030 0.038 0.762 0.965
C 0.0034 0.006 0.086 0.152
D 0.105 0.120 2.667 3.048
E 0.047 0.055 1.194 1.397
e 0.070 0.080 1.778 2.032
e1 0.071 0.079 1.803 2.007
H 0.082 0.098 2.083 2.489
L 0.004 0.012 0.102 0.305
ASM161 / ASM162
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Notice: The information in this document is subject to change without notice
µP Supervisory Circuit
rev 1.0
October 2003
Ordering Information
Notes: 1. Tape and Reel packaging is indicated by the /T designation.
Part Number1
Reset
Threshold
(V)
Temperature
Range
(°C)
Pin-Package Package Marking
(XX Lot Code)
ASM161LCUS/T 4.63 0 TO 70 4-SOT-143 1LXX
ASM161MCUS/T 4.38 0 TO 70 4-SOT-143 1MXX
ASM161JCUS/T 4.00 0 TO 70 4-SOT-143 1JXX
ASM161TCUS/T 3.08 0 TO 70 4-SOT-143 1TXX
ASM161SCUS/T 2.93 0 TO 70 4-SOT-143 1SXX
ASM161RCUS/T 2.63 0 TO 70 4-SOT-143 1RXX
ASM162LCUS/T 4.63 0 TO 70 4-SOT-143 2LXX
ASM162MCUS/T 4.38 0 TO 70 4-SOT-143 2MXX
ASM162JCUS/T 4.00 0 TO 70 4-SOT-143 2JXX
ASM162TCUS/T 3.08 0 TO 70 4-SOT-143 2TXX
ASM162SCUS/T 2.93 0 TO 70 4-SOT-143 2SXX
ASM162RCUS/T 2.63 0 TO 70 4-SOT-143 2RXX
ASM161LEUS/T 4.63 -40 TO 85 4-SOT-143 3LXX
ASM161MEUS/T 4.38 -40 TO 85 4-SOT-143 3MXX
ASM161JEUS/T 4.00 -40 TO 85 4-SOT-143 3JXX
ASM161TEUS/T 3.08 -40 TO 85 4-SOT-143 3TXX
ASM161SEUS/T 2.93 -40 TO 85 4-SOT-143 3SXX
ASM161REUS/T 2.63 -40 TO 85 4-SOT-143 3RXX
ASM162LEUS/T 4.63 -40 TO 85 4-SOT-143 4LXX
ASM162MEUS/T 4.38 -40 TO 85 4-SOT-143 4MXX
ASM162JEUS/T 4.00 -40 TO 85 4-SOT-143 4JXX
ASM162TEUS/T 3.08 -40 TO 85 4-SOT-143 4TXX
ASM162SEUS/T 2.93 -40 TO 85 4-SOT-143 4SXX
ASM162REUS/T 2.63 -40 TO 85 4-SOT-143 4RXX
Alliance Semiconductor Corporation
2575, Augustine Drive,
Santa Clara, CA 95054
Tel: 408 - 855 - 4900
Fax: 408 - 855 - 4999
www.alsc.com
Copyright © Alliance Semiconductor
All Rights Reserved
Part Number: ASM161 / ASM162
Document Version: 1.0
© Copyright 2003 Alliance Semiconductor Corporation. All rights reserved. Our three-point logo, our name and Intelliwatt are trademarks or
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appear in this document. The data contained herein represents Alliance's best data and/or estimates at the time of issuance. Alliance reserves the
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ASM161 / ASM162
