ASM161JCUS/T ALSC [Alliance Semiconductor Corporation], ASM161JCUS/T Datasheet - Page 3

• Manufacturer Part Number: ASM161JCUS/T
• Description: uP Supervisory Circuit
• Manufacturer: ALSC [Alliance Semiconductor Corporation]

October 2003
rev 1.0
Detailed Descriptions
The reset function ensures the microprocessor is properly
reset and powers up into a known condition after a power
failure.
Reset Timing
A reset is generated whenever the supply voltage is below
the threshold level (V
800ms after V
guaranteed to be no more than 2 seconds. The rest signal
remains active as long as the monitored supply voltage is
below the internal threshold voltage.
The ASM161 has an open-drain, active LOW RESET output
(which is guaranteed to be in the correct state for V
to 1.1 V). The ASM161 uses an external pull-up resistor.
Output leakage current is under 1µA. A high resistance value
can be used to minimize current drain.
The ASM162 generates an active-HIGH RESET output.
Manual Reset
The ASM161/162 have a unique manual reset circuit. A
negative going edge transition on MR initiates the reset. A
manual reset generates a single reset pulse of fixed length.
The output-reset pulse remains asserted for the Reset Active
Time-Out Period t
completed, the MR input remains disabled for at least 49µS
but not more than 122µS. This period is specified as t
During the MR disabled period, the microcontroller is
guaranteed a time period free of new manual reset signals.
This period can be used to refresh critical DRAM contents or
other system tasks.
Part Number
ASM161
ASM162
CC
RP
has risen above the reset threshold and is
and then clears. Once the reset pulse is
CC
LOW (use external pull-up resistor)
< V
TH
). The reset duration is at least
Reset Polarity
Notice: The information in this document is subject to change without notice
HIGH
µP Supervisory Circuit
CC
MRD
down
.
The MR pin must be taken HIGH and LOW again after the
t
pulse.
The manual reset input has an internal 20kΩ pull-up resistor.
MR can be left open if not used.
Application Information
Glitch Resistance
The ASM161/162 are relatively immune to short duration
negative-going V
goes 100mV below the reset threshold and lasts 20s or less
will not typically cause a reset pulse.
Valid Reset with V
To ensure that logic inputs connected to the ASM162 RESET
pin are in a known state when V
pull-down resistor at RESET is needed. The value is not
critical.
This scheme does not work with the open-drain outputs of
ASM161.
MRD
t
MD
MR
RESET
period has been completed to initiate another reset
*........
Time-Out
Reset
Triggering
Figure 2: RESET valid with VCC under 1.1V
Pulse
*Second and following edges ignored
CC
Figure 1: Manual Reset Timing
Power Supply
CC
MR input is blocked
transients/glitches. A V
under 1.1V
ASM161 / ASM162
MR
t
MRD
ASM162
V
GND
CC
CC
RESET
is under 1.1V, a 100kΩ
CC
transient that
100KΩ
3 of 9
Ready
next
for
MR