October 2003
rev 1.0
ASM811, ASM812
SOT143
GND
1
ASM811
(ASM812)
Pin Diagram:
Block Diagram
4
V
CC
V
CC
20kΩ
MR
V
CC
3
MR
(RESET) RESET
2
+
-
+
-
RESET Generator
4.63V
4.38V
4.38V
4.00V
3.08V
2.93V
2.63V
RESET
(RESET)
ASM811
(ASM812)
Pin Description
GND
Pin #
ASM811
1
2
ASM812
1
-
Pin
Name
GND
RESET
Ground.
Function
RESET is asserted LOW if V
CC
falls below V
TH
and remains LOW for T
RST
after V
CC
exceeds
the Threshold. In addition, RESET is active LOW as long as the manual reset is low.
RESET is asserted HIGH if V
CC
falls below V
TH
and remains HIGH for T
RST
after V
CC
exceeds
the threshold. In addition, RESET is active HIGH as long as the manual reset is low.
Manual Reset Input. A logic LOW on MR asserts reset. Reset remains active as long as MR is
LOW and for T
MRST
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.
Power supply input voltage (3.0V, 3.3V, 5.0V)
-
2
RESET
3
3
MR
4
4
V
CC
Detailed Description
Manual Reset (MR) Input
A
proper
reset
input
enables
a
microprocessor
/
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.
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 V
CC
supply voltage falls below the
threshold trip voltage and remains asserted for 140ms
minimum after the V
CC
has risen above the threshold.
4 Pin µP Voltage Supervisor with Manual Reset
Notice: The information in this document is subject to change without notice
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ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
