February 2005
rev 1.4
ASM1812
Low Power 5V µP Reset Active HIGH, Push-Pull Output
Applications
•
•
•
•
•
•
•
Set-top boxes
Cellular phones
PDAs
Energy management systems
Embedded control systems
Printers
Single board computers
General Description
The ASM1812 is a voltage supervisory device with low-power,
5V µP Reset, active HIGH, Push-Pull output. Maximum supply
current over temperature is a low 20µA.
The ASM1812 issues an active HIGH 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 HIGH 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 ASM1812 is designed with a push-pull output stage and
operates over the extended industrial temperature range.
Devices are available in TO-92 and compact surface mount
SOT-23 packages.
Other low power products in this family include the ASM1810/
11/15/16/17, ASM1233D and ASM1233M.
Typical Operating Circuit
V
CC
ASM1812
Microprocessor
RESET
RESET
GND
Key Features
•
•
•
•
•
•
•
•
•
Low Supply Current
•20 µA 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 HIGH power-up reset
Precision temperature-compensated voltage reference and
comparator
Eliminates external components
TO-92 and compact surface mount SOT-23 package
Push-Pull output for minimum current drain
Operating temperature -40°C to +85°C
Reference
Supply
Tolerance
Bias
Block Diagram
V
CC
2
ASM1812
+
Delay
150ms
Typical
1
-
RESET
3
GND
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
February 2005
rev 1.4
ASM1812
Application Information
Operation - Power Monitor
The
ASM1812
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 (HIGH) 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.
V
CC
V
CCTP
(MIN)
t
R
V
CCTP
(MAX)
V
CCTP
~
~
t
RPU
~
~
RESET
V
OL
ASM1812
Microprocessor
RESET
RESET
Figure 2: Timing Diagram: Power-Up
Figure 1: Typical Application
V
CC
t
F
V
CCTP
(MAX)
V
CCTP
V
CCTP
(MIN)
~
~
t
RPD
V
OH
RESET Slews with V
CC
~
~
RESET
Figure 3: Timing Diagram: Power-Down
Low Power 5V µP Reset
Notice: The information in this document is subject to change without notice
3 of 9
February 2005
rev 1.4
ASM1812
Absolute Maximum Ratings
Parameter
Voltage on V
CC
Voltage on RESET
Operating Temperature Range
Soldering Temperature (for 10 sec)
Storage Temperature
-55
Min
-0.5
-0.5
-40
Max
7
V
CC
+ 0.5
85
260
125
Unit
V
V
°C
°C
°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 rat-
ings for prolonged periods of time may affect device reliability.
Electrical Characteristics
Unless otherwise noted, V
CC
= 1.2V to 5.5V and specifications are over the operating temperature range of -40°C to +85°C. All voltages are referenced
toground
Parameter
Supply Voltage
Output Voltage
Output Current
Output Current
Operating Current
V
CC
Trip Point (ASM1812R-5)
V
CC
Trip Point (ASM1812R-10)
V
CC
Trip Point (ASM1812R-15)
Output Capacitance
RESET Active Time
V
CC
Detect to RESET HIGH
V
CC
Slew Rate
V
CC
Slew Rate
V
CC
Detect to RESET LOW
Symbol
V
CC
V
OH
I
OH
I
OL
I
CC
V
CCTP
V
CCTP
V
CCTP
C
OUT
t
RESET
t
RPD
t
F
t
R
t
RPU
t
r
= 5µs
Conditions
Min
1.2
Typ
Max
5.5
Unit
V
V
µA
mA
I
OUT
< 500 µA
Output = 2.4V, V
CC
> 2.7V
Output = 0.4V, V
CC
> 2.7V
V
CC
< 5.5V, RESET output
V
CC
- 0.5V
V
CC
- 0.1V
350
+10
8
4.50
4.25
4.00
4.62
4.35
4.13
20
4.75
4.49
4.24
10
100
150
2
300
0
100
150
300
250
5
µA
V
V
V
pF
ms
µs
µs
ns
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.
Low Power 5V µP Reset
Notice: The information in this document is subject to change without notice
4 of 9
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