October 2006
ASM1832
rev 1.6
.
Detailed Description
The
ASM1832
monitors
the
microprocessor
or
TRIP Point Voltage
(V)
microcontroller power supply and issues reset signals, both
active HIGH and active LOW, that halt processor operation
whenever the power supply voltage levels are outside a
predetermined tolerance.
Tolerance
Select
Tolerance
Min
Nom
Max
TOL = VCC
TOL = GND
20%
10%
2.47
2.80
2.55
2.88
2.64
2.97
RESET and RESET outputs
RESET and RESET signals are active for a minimum of
250ms after the supply has returned to in-tolerance level.
This allows the power supply and monitored processor to
stabilize before instruction execution is allowed to begin.
t
R
V
(MAX)
CCTP
Trip Point Tolerance Selection
V
CCTP
V
(MIN)
CCTP
The TOL input is used to determine the level VCC can vary
t
below 3.3V without asserting a reset. With TOL conected to
RPU
V
CC
RESET
RESET
V
CC, RESET and RESET become active whenever VCC falls
below 2.64V. RESET and RESET become active when the
CC falls below 2.98V if TOL is connected to ground.
V
OH
V
V
OL
After VCC has risen above the trip point set by TOL, RESET
Figure 1: Timing Diagram : Power Up
and RESET remain active for a minimum time period of
250ms. On power-down, once VCC falls below the reset
threshold RESET stays LOW and is guaranteed to be 0.4V or
less until VCC drops below 1.2V. The reset output on the
t
F
V
CC
V
(MAX)
ASM1832 uses a push-pull drive stage that can maintain a
valid output below 1.2V. To sink current with VCC below 1.2V,
CCTP
V
CCTP
V
(MIN)
CCTP
a resistor can be connected from the reset pin (RESET) to
Ground. This configuration will give a valid value on the reset
output with VCC approaching 0V. During both power up and
RESET
RESET
t
RPD
down, the configuration will draw current when the RESET is
in the high state. The value of 100KΩ should be adequate to
maintain a valid condition. The active HIGH reset signal is
valid down to a VCC level of 1.2V also.
V
OH
V
OL
Figure 2: Timing Diagram : Power Down
Microprocessor
ASM1832
Application Information
RESET
RESET
Manual Reset Operation
Push-button switch input, PBRST, allows the user to override
the internal trip point detection circuits and issue reset
100kΩ
3.3V µP Power Supply Monitor and Reset Circuit
3 of 9
Notice: The information in this document is subject to change without notice
PULSECORE [ PulseCore Semiconductor ]
