ASM1811
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 1.4
Low Power 5V P Reset Active LOW, Open - Drain Output
February 2005
General Description
The ASM1811 is a voltage supervisory device with a low-power,
5V P Reset, active LOW, open-drain output. Maximum supply
current over temperature is a low 20A.
The ASM1811 generates an active LOW reset signal whenever
the monitored supply is out of tolerance. A precision reference
and comparator circuit monitor power supply (V
CC
) level.
Tolerance level options are 5%, 10% and 15%. When an out-of-
tolerance condition is detected, an internal power-fail signal is
generated which forces an active LOW reset signal. After V
CC
returns to an in-tolerance condition, the reset signal remains
active for 150ms to allow the power supply and system
microprocessor to stabilize.
The ASM1811 is designed with a open-drain output stage and
operates over the extended industrial temperature range.
Devices are available in low cost TO-92 and compact surface
mount SOT-23 packages.
Other low power products in this family include the ASM1810/
12/15/16/17, ASM1233D and ASM1233M.
Key Features
Low Supply Current
20 A maximum (5.5 V)
Automatically restarts a microprocessor after power failure
150ms reset delay after V
CC
returns to an in-tolerance con-
dition
Active LOW power-up reset
Precision temperature-compensated voltage reference and
comparator
Eliminates external components
Low cost TO-92 and compact surface mount SOT-23 pack-
ages
Operating temperature -40C to +85C
Applications
Set-top boxes
Cellular phones
PDAs
Energy management systems
Embedded control systems
Printers
Single board computers
Typical Operating Circuit
Block Diagram
Microprocessor
V
CC
RESET
RESET
GND
ASM1811
V
CC
Supply
Reference
Delay
150ms
Typical
Tolerance
Bias
+
-
2
ASM1811
V
CC
Supply
Delay
150ms
Typical
Tolerance
Bias
-
GND
RESET
Reference
+
1
3
5.5K
3 of 9
Notice: The information in this document is subject to change without notice
Low Power 5V P Reset
ASM1811
rev 1.4
February 2005
Application Information
Operation - Power Monitor
The ASM1811 detects out-of-tolerance power supply
conditions. It resets a processor during power-up, power-
down and issues a reset to the system processor when the
monitored power supply voltage is below the reset threshold.
When an out-of-tolerance V
CC
voltage is detected, the
RESET signal is asserted. On power-up, RESET is kept
active (LOW) for approximately 150ms after the power supply
voltage has reached the selected tolerance. This allows the
power supply and microprocessor to stabilize before RESET
is released.
~~
t
RPU
V
CCTP
(MIN)
~~
V
OH
V
CCTP
V
CCTP
(MAX)
t
R
V
CC
RESET
Figure 1: Timing Diagram: Power-Up
~ ~
V
CCTP
(MIN)
V
CCTP
V
CCTP
(MAX)
t
F
V
CC
t
RPD
V
OL
RESET
Figure 2: Timing Diagram: Power-Down
ASM1811
4 of 9
Notice: The information in this document is subject to change without notice
Low Power 5V P Reset
rev 1.4
February 2005
Absolute Maximum Ratings
Electrical Characteristics
Unless otherwise noted, V
CC
= 1.2V to 5.5V and specifications are over the operating temperature range of -40C to +85C. All voltages
are
referenced to ground
Parameter
Min
Max
Unit
Voltage on V
CC
-0.5
7
V
Voltage on RESET
-0.5
V
CC
+ 0.5
V
Operating Temperature Range
-40
85
C
Soldering Temperature (for 10 sec)
260
C
Storage Temperature
-55
125
C
ESD rating
HBM
MM
2
200
KV
V
NOTE: These are stress ratings only and functional use is not implied. Exposure to absolute maximum ratings for prolonged
periods of time may affect device reliability.
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Supply Voltage
V
CC
1.2
5.5
V
Operating Current
I
CC
V
CC
< 5.5V, RESET output open
8
20
A
V
CC
Trip Point (ASM1811R-5)
V
CCTP
4.50
4.62
4.75
V
V
CC
Trip Point (ASM1811R-10)
V
CCTP
4.25
4.35
4.49
V
V
CC
Trip Point (ASM1811R-15)
V
CCTP
4.00
4.13
4.24
V
Internal Pull-up Resistor
R
P
3.5
5.5
7.5
k
Output Capacitance
C
OUT
10
pF
RESET Active Time
t
RESET
100
150
250
ms
V
CC
Detect to RESET Low
t
RPD
2
5
s
V
CC
Slew Rate
(V
CCTP
(MAX) to V
CCTP
(MIN)
t
F
300
s
V
CC
Slew Rate
(V
CCTP
(MIN) to V
CCTP
(MAX)
t
R
0
ns
V
CC
Detect to RESET High
t
RPU
t
r
= 5s
100
150
300
ms
Note: The t
F
value is for reference in defining values for t
RPD
and should not be considered for proper operation or use.
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