ASM811, ASM812
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
October 2003
rev 1.0 4 Pin µP Voltage Supervisor with Manual Reset
General Description
The ASM811/ASM812 are cost effective low power supervisors
designed to monitor voltage levels of 3.0V, 3.3V and 5.0V
power supplies in low-power microprocessor (µP),
microcontroller (µC) and digital systems. They provide excellent
reliability by eliminating external components and adjustments.
A reset signal is issued if the power supply voltage drops below
a preset reset threshold and is asserted for at least 140ms after
the supply has risen above the reset threshold. The ASM811
has an active-low output RESET that is guaranteed to be in the
correct state for VCC down to 1.1V. The ASM812 has an active-
high RESET output. The reset comparator is designed to ignore
fast transients on VCC. A debounced manual reset input allows
the user to manually reset the systems to bring them out of
locked state.
Low power consumption makes the ASM811/ASM812 ideal for
use in portable and battery operated equipment. The ASM811/
ASM812 are available in a compact 4-pin SOT-143 package
and thus use minimal board space.
Six voltage thresholds are available to support 3V to 5V
systems:
Features
• New 4.0V threshold option
• 9µA supply current
• Monitor 5V, 3.3V and 3V supplies
• Manual reset input
• 140ms min. reset pulse width
• Guaranteed over temperature
• Active-low reset valid with 1.1V supply (ASM811)
• Small 4-pin SOT-143 package
• No external components
• Power-supply transient-immune design
RESET THRESHOLD
Suffix Voltage
L4.63
M4.38
J4.00
T3.08
S2.93
R2.63
Applications
• Computers and Controllers
• Embedded controllers
• Portable/Battery operated systems
• Intelligent instruments
• Wireless communication systems
• PDAs and handheld equipment
• Automotive systems
• Safety Systems
Typical Operating Circuit
V
CC
V
CC
V
CC
µP
RESET
Input
RESET
(RESET)
GND
GND
(RESET)
MR
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Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
ASM811, ASM812
October 2003
rev 1.0
Pin Diagram: Block Diagram
Pin Description
Pin # Pin
Name Function
ASM811 ASM812
1 1 GND Ground.
2 - RESET RESET is asserted LOW if VCC falls below VTH and remains LOW for TRST after VCC exceeds
the Threshold. In addition, RESET is active LOW as long as the manual reset is low.
-2RESET
RESET is asserted HIGH if VCC falls below VTH and remains HIGH for TRST after VCC exceeds
the threshold. In addition, RESET is active HIGH as long as the manual reset is low.
33MR
Manual Reset Input. A logic LOW on MR asserts reset. Reset remains active as long as MR is
LOW and for TMRST after MR returns HIGH. The active low input has an internal 20kΩ pull-up
resistor. The input should be left open if not used. It can be driven by TTL or CMOS logic or
shorted to ground by a switch.
44
VCC Power supply input voltage (3.0V, 3.3V, 5.0V)
Detailed Description
A proper reset input enables a microprocessor /
microcontroller to start in a known state. ASM811/812 assert
reset to prevent code execution errors during power-up, power-
down and brown-out conditions.
Reset Timing
The reset signal is asserted- LOW for the ASM811 and HIGH
for the ASM812- when the VCC supply voltage falls below the
threshold trip voltage and remains asserted for 140ms
minimum after the VCC has risen above the threshold.
Manual Reset (MR) Input
A logic low on MR assserts RESET LOW on the ASM811 and
RESET HIGH on the ASM812. MR is internally pulled high
through a 20kΩ resistor and can be driven by TTL/CMOS gates
or with open collector/drain outputs. MR can be left open if not
used. MR may be connected to ground through a normally-
open momentary switch without an external debounce circuit.
A 0.1µF capacitor from MR to ground can be added for
additional noise immunity.
1
23
SOT143
ASM811
(ASM812)
GND
RESET
V
CC
(RESET)
4
MR
+
-
RESET Generator
-
+
VCC RESET
(RESET)
GND
ASM811
(ASM812)
4.38V
4.00V
3.08V
2.93V
2.63V
4.38V
4.63V
MR
20kΩ
VCC
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Notice: The information in this document is subject to change without notice
ASM811, ASM812
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
Reset Output Operation
In µP / µC systems it is important to have the processor and
the system begin operation from a known state. A reset
output to a processor is provided to prevent improper
operation during power supply sequencing or low voltage
brown-out conditions.
The ASM811/812 are designed to monitor the system power
supply voltages and issue a reset signal when the levels are
out of range. RESET outputs are guaranteed to be active for
VCC above 1.1V. When VCC exceeds the reset threshold, an
internal timer keeps RESET active for the reset timeout
period, after which RESET becomes inactive (HIGH for the
ASM811 and LOW for the ASM812). If VCC drops below the
reset threshold, RESET automatically becomes active.
Alternatively, external circuitry or an operator can initiate this
condition using the Manual Reset (MR) pin. MR can be left
open if it is not used. MR can be driven by TTL/CMOS logic
or even an external switch.
Valid Reset with VCC under 1.1V
To ensure logic inputs connected to the ASM811 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.
A 100kΩ pull-up resistor to VCC is needed with the ASM812.
Application Information
Negative VCC Transients
Typically short duration transients of 100mV amplitude and
20µs duration do not cause a false RESET. A 0.1µF capacitor
at VCC increses transient immunity.
Bidirectional Reset Pin Interfacing
The ASM811/812 can interface with µP / µC bi-directional
reset pins by connecting a 4.7kΩ resistor in series with the
ASM811/812 reset output and the µP/µC bi-directional reset
input pin.
Power supply
BUF Buffered
RESET
V
CC
ASM811
GND GND
RESET RESET
Input
µC or µP
4.7k
Ω
Bi-directional I/O Pin
Figure 4: Bi-directional Reset Pin Interface
MR
V
CC
Power Supply
ASM811
RESET
GND 100k
Ω
V
CC
Power Supply
ASM812
RESET
GND
MR MR
100k
Ω
0V
5V
V
CC
V
TH
T
RST
T
MRST
5V
0V
5V
0V
5V
0V
MR
RESET
RESET
ASM811
ASM812
Figure 1: Reset Timing and Manual Reset (MR)
Figures 2 & 3: RESET valid with VCC under 1.1V
ASM811, ASM812
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Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
Absolute Maximum Ratings, Table 1:
Absolute Maximum Ratings, Table 2:
Parameter Min Max Units
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
Output current: RESET, RESET 20 mA
Rate of Rise at VCC 100 V/µs
Note: These are stress ratings only and the functional operation is not implied. Exposure
to absolute maximum ratings for prolonged time periods may affect device reliability.
Parameter Min Max Units
Power Dissipation (TA = 70°C)
Derate SOT-143 4mW/°C above 70°C 320 uW
Operating temperature range -40 105 °C
Storage temperature range -65 160 °C
Lead temperature (Soldering, 10 sec) 300 °C
Note: These are stress ratings only and the functional operation is not implied. Exposure to absolute
maximum ratings for prolonged time periods may affect device reliability.
ASM811, ASM812
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Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
Electrical Characteristics:
Unless otherwise noted, VCC is over the full voltage range, TA = -40°C to 105°C.
Typical values at TA = 25°C, VCC = 5V for L/M/J devices, VCC = 3.3V for T/S devices and VCC = 3V for R devices.
Symbol Parameter Conditions Min Typ Max Unit
VCC Input Voltage Range TA = 0°C to 70°C
TA = -40°C to 105°C
1.1
1.2
5.5
5.5
V
V
ICC Supply Current (Unloaded)
TA= -40°C to 85°C
TA = -40°C to 85°C
TA = 85°C to 105°C
TA = 85°C to 105°C
VCC < 5.5V, L/M/J
VCC < 3.6V, R/S/T
VCC < 5.5V, L/M/J
VCC < 3.6V, R/S/T
9
6.8
15
10
25
20
µA
VTH Reset Threshold
L devices
TA = 25°C
TA = -40°C to 85°C
TA = 85°C to 105°C
4.56
4.50
4.40
4.63
4.70
4.75
4.86
V
M devices
TA = 25°C
TA = -40°C to 85°C
TA = 85°C to 105°C
4.31
4.25
4.16
4.38
4.45
4.50
4.56
J devices
TA = 25°C
TA = -40°C to 85°C
TA = 85°C to 105°C
3.93
3.89
3.80
4.00
4.06
4.10
4.20
T devices
TA = 25°C
TA = -40°C to 85°C
TA = 85°C to 105°C
3.04
3.00
2.92
3.08
3.11
3.15
3.23
S devices
TA = 25°C
TA = -40°C to 85°C
TA = 85°C to 105°C
2.89
2.85
2.78
2.93
2.96
3.00
3.08
R devices
TA = 25°C
TA = -40°C to 85°C
TA = 85°C to 105°C
2.59
2.55
2.50
2.63
2.66
2.70
2.76
TCVTH Reset Threshold Temp.
Coefficient 30 ppm/°C
VCC to Reset Delay VCC = VTH to (VTH - 125mV), 60 µs
Reset Active Timeout Period
TA = 0°C to 70°C 140
100 240
560
840 ms
TA = -40°C to 105°C
tMR MR Minimum Pulse Width 10 µs
Notes:
1. Production testing done at TA = 25°C. Over-temperature specifications guaranteed by design only using six sigma design limits.
2. RESET output is active LOW for the ASM811 and RESET output is active HIGH for the ASM812.
3. Glitches of 100ns or less typically will not generate a reset pulse.
ASM811, ASM812
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Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
MR Glitch Immunity Note 3 100 ns
tMD MR to RESET Propogation
Delay Note 2 0.5 µs
VIH
MR Input Threshold VCC > VTH (MAX),
ASM811/812L/M/J
2.3
V
VIL 0.8
VIH
MR Input Threshold VCC > VTH (MAX),
ASM811/812R/S/T
0.77VCC
V
VIL 0.25VCC
MR Pullup Resistance 10 20 30 kΩ
VOL Low RESET Output Voltage
(ASM811)
VCC= VTH min., ISINK = 1.2mA,
ASM811R/S/T
0.3
0.4
0.3
V
VCC= VTH min., ISINK = 3.2mA,
ASM811L/M/J
VCC > 1.1V, ISINK = 50µA
VOH High RESET Output Voltage
(ASM811)
VCC > VTH max., ISOURCE = 500µA,
ASM811R/S/T 0.8VCC
VCC - 1.5
V
VCC > VTH max., ISOURCE = 800µA,
ASM811L/M/J
VOL Low RESET Output Voltage
(ASM812)
VCC= VTH max., ISINK = 1.2mA,
ASM812R/S/T 0.3
0.4
V
VCC= VTH max., ISINK = 3.2mA,
ASM812L/M/J
VOH High RESET Output Voltage
(ASM812) 1.8V < VCC < VTH min., ISOURCE = 150µA 0.8VCC V
TRST Active Reset Timeout Period VCC > VTH 140 240 msec
TMRST Manual Active Reset Time-
out Period MR returns HIGH 180 msec
Symbol Parameter Conditions Min Typ Max Unit
Notes:
1. Production testing done at TA = 25°C. Over-temperature specifications guaranteed by design only using six sigma design limits.
2. RESET output is active LOW for the ASM811 and RESET output is active HIGH for the ASM812.
3. Glitches of 100ns or less typically will not generate a reset pulse.
ASM811, ASM812
7 of 10
Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
Typical Operating Characteristics
Unless otherwise noted, VCC is over the full voltage range, TA = -40°C to 105°C. Typical values at TA = 25°C,
VCC = 5V for L/M/J devices, VCC = 3.3V for T/S devices and VCC = 3V for R devices.
Normalised Reset Threshold vs Temperature
0.95
0.96
0.97
0.98
0.99
1
1.01
1.02
-40 -20 0 20 40 60 80 100 125
Temperature (°C)
Normalised Reset
Threshold
Reset Timeout Period vs Temperature
0
50
100
150
200
250
300
350
400
-40 -20 0 20 40 60 80 100 125
Temperature (°C)
Reset Timeout Period
(ms)
ASM811T
ASM811R
ASM811T
ASM811R
Supply Current vs Temperature
0
2
4
6
8
10
-40 -20 0 20 40 60 80 100 125
Temperature (°C)
Supply Current (µA)
ASM811R
ASM811T
ASM811, ASM812
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Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
Package Dimensions:
Plastic SOT-143 (4-Pin)
Inches Millimeters
Min Max Min Max
A0.031 0.047 0.787 1.194
A1 0.001 0.005 0.025 0.127
B0.014 0.022 0.356 0.559
B1 0.030 0.038 0.762 0.965
C0.0034 0.006 0.086 0.152
D0.105 0.120 2.667 3.048
E0.047 0.055 1.194 1.397
e0.070 0.080 1.778 2.032
e1 0.071 0.079 1.803 2.007
H0.082 0.098 2.083 2.489
L0.004 0.012 0.102 0.305
EH
e
D
A
A1 eC
L
a = 0° -8°
B
e1
B1
ASM811, ASM812
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Notice: The information in this document is subject to change without notice
4 Pin µP Voltage Supervisor with Manual Reset
October 2003
rev 1.0
Ordering Information:
Related Products:
Part Number 1Reset Threshold (V) Temperature Range Pin-Package Package Marking
(XX Lot Code)
ASM811 ACTIVE LOW RESET
ASM811LEUS-T 4.63 -40°C to +105°C 4-SOT143 SMXX
ASM811MEUS-T 4.38 -40°C to +105°C 4-SOT143 SNXX
ASM811JEUS-T 4.00 -40°C to +105°C 4-SOT143 SOXX
ASM811TEUS-T 3.08 -40°C to +105°C 4-SOT143 SPXX
ASM811SEUS-T 2.93 -40°C to +105°C 4-SOT143 SQXX
ASM811REUS-T 2.63 -40°C to +105°C 4-SOT143 SRXX
ASM812 ACTIVE HIGH RESET
ASM812LEUS-T 4.63 -40°C to +105°C 4-SOT143 SSXX
ASM812MEUS-T 4.38 -40°C to +105°C 4-SOT143 STXX
ASM812JEUS-T 4.00 -40°C to +105°C 4-SOT143 SUXX
ASM812TEUS-T 3.08 -40°C to +105°C 4-SOT143 SVXX
ASM812SEUS-T 2.93 -40°C to +105°C 4-SOT143 SWXX
ASM812REUS-T 2.63 -40°C to +105°C 4-SOT143 SXXX
Notes:
1. Tape and Reel packaging is indicated by the -T designation.
ASM809 ASM810 ASM811 ASM812
Max Supply Current 15µA 15µA 15µA 15µA
Package Pins 3 3 4 4
Manual RESET input
Package Type SOT - 23 SOT - 23 SOT - 143 SOT - 143
Active-HIGH RESET Output
Active-LOW RESET Output
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: ASM811, ASM812
Document Version: v 1.0
© Copyright 2003 Alliance Semiconductor Corporation. All rights reserved. Our three-point logo, our name and Intelliwatt are trademarks or
registered trademarks of Alliance. All other brand and product names may be the trademarks of their respective companies. Alliance reserves the
right to make changes to this document and its products at any time without notice. Alliance assumes no responsibility for any errors that may
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ASM811, ASM812
