ASM1233A
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
Low Power, 3.3V, P Reset, Active LOW, Open-Drain Output
November 2003
General Description
The ASM1233A is a voltage supervisor with low-power, 3.3V
P Reset, with an active LOW, open-drain output. Maximum
supply current over temperature is a low 15A.
The ASM1233A 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. The tolerance is 15% for the 3.3V, ASM1233A. 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 350ms to allow the power supply and system
microprocessor to stabilize.
The ASM1233A is designed with a open-drain output stage and
operates over the extended industrial temperature range.
Devices are available in compact SOT-223 packages.
Other low power products in this family include the ASM1810/
11/12/15/16/17, ASM1233D, and ASM1233M
Key Features
Low Supply Current
15A maximum (3.6 V)
Automatically restarts a microprocessor after power failure
350ms reset delay after V
CC
returns to an in-tolerance con-
dition
Active LOW power-up reset, 5k
internal pull-up
Precision temperature-compensated voltage reference and
comparator
Eliminates external components
Low-cost SOT-223 package
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
GND
Supply
Reference
Delay
350ms
Typical
Tolerance
Bias
+
-
Microprocessor
ASM1233A
V
CC
RESET
Delay
Typical
+
-
V
CC
RESET
RESET
GND
ASM1233A
5.0k
3 of 9
Notice: The information in this document is subject to change without notice
Low Power, 3.3V, P Reset, Active LOW, Open-Drain Output
ASM1233A
rev 1.0
November 2003
Application Information
Operation - Power Monitor
The ASM1233A detects out-of-tolerance power supply
conditions. It resets a processor during power-up, power-
down and generates 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 approximatley 350ms after the power supply
voltage has reached the selected tolerance. This allows the
power supply and microprocessor to stablize 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
ASM1233A
4 of 9
Notice: The information in this document is subject to change without notice
Low Power, 3.3V, P Reset, Active LOW, Open-Drain Output
rev 1.0
November 2003
Absolute Maximum Ratings
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
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.
ASM1233A
5 of 9
Notice: The information in this document is subject to change without notice
Low Power, 3.3V, P Reset, Active LOW, Open-Drain Output
rev 1.0
November 2003
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
Symbol
Conditions
Min
Typ
Max
Unit
Supply Voltage
V
CC
1.2
5.5
V
Output Voltage
V
OH
I
OUT
< 500 A
V
CC
- 0.5V
V
CC
- 0.1V
V
Output Current
I
OL
Output = 0.4V, V
CC
>= 2.7V
+8
mA
Operating Current
I
CC
V
CC
< =3.6V, RESET output
open
6
15
A
V
CC
Trip Point (ASM1233A-3)
V
CCTP
2.64
2.72
2.8
V
Voltage High Trip Level
ASM1233A-3
V
HTL
3.14
V
Internal Pull-up Resistor
R
P
3.5
5.0
7.5
k
Output Capacitance
C
OUT
10
pF
V
CC
Detect to RESET Low
t
RPD
2
10
s
V
CC
Slew Rate
(V
HTL
- V
LTL
)
t
F
300
s
V
CC
Slew Rate
(V
LTL
- V
HTL
)
t
R
0
ns
V
CC
Detect to RESET High
t
RPU
t
r
= 5s
200
350
500
ms
Note: A 1k
resistor maybe required in some applications for proper operation of the microprocessor reset control circuit.
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