ISSUE 2 - MARCH 2000
ZXCM209
ZXCM210
APPLICATIONS INFORMATION
Negative going V
CC
transients
The ZXCM209/210 are, to a good degree, immune to
short duration negative going supply transients. Under
certain circumstances very brief transients are allowed
without inappropriate false triggering of the reset
circuit.Theresponseto supply transients is showninthe
Noise Immunity graph in the typical characteristics. The
graph indicates the typical allowable transient duration
for a specified threshold overdrive such that a reset
pulse is not generated. Addition of a bypass capacitor,
e.g.0.1μF, as close as possible to the V
CC
pin willprovide
extra transient immunity.
Reset valid down to very low supply voltages
With V
CC
between 0V and 1V the output of the
ZXCM209/210 may be in an undefined state. In many
systems
this
is
inconsequential
microprocessor, and other circuits, will be inoperative
with supplies this low. In applications where this is
important, the addition of an external resistor ensures
that the reset output remains valid for V
CC
< 1V. The
resistor value is non critical: a value of 100k
is
recommended. For the ZXCM209 the resistor should
be applied between reset output and ground: for the
ZXCM210 between reset output and V
CC
. Figure 1
shows the connection diagram for the ZXCM devices
in these configurations.
as
the
v
cc
ZXCM210
Reset
Output
Gnd
v
cc
Micro
Reset
Input
Gnd
v
cc
100k
v
cc
ZXCM209
Reset
Output
Gnd
v
cc
Micro
Reset
Input
Gnd
v
cc
100k
Figure 1
Circuit for operation of ZXCM with reset valid down to very low supply voltage.
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