3-Pin, Ultra-Low-Power SC70/SOT
µP Reset Circuits
MAX6326/MAX6327/MAX6328/MAX6346/MAX6347/MAX6348
____________ Applications Information
Interfacing to µPs with
Bidirectional Reset Pins
Since the
RESET
output on the MAX6328/MAX6348 is
open drain, these devices interface easily with micro-
processors (µPs) that have bidirectional reset pins,
such as the Motorola 68HC11. Connecting the µP
supervisor’s
RESET
output directly to the microcon-
troller’s (µC’s)
RESET
pin with a single pull-up resistor
allows either device to assert reset (Figure 1).
V
CC
V
CC
V
CC
MAX6328
MAX6348
µP
RESET
RESET
INPUT
MOTOROLA
68HCXX
Negative-Going V
CC
Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, these devices
are relatively immune to short-duration, negative-going
V
CC
transients (glitches).
The
Typical Operating Characteristics
show the Maxi-
mum Transient Duration vs. Reset Threshold Overdrive
graph, for which reset pulses are not generated. The
graph shows the maximum pulse width that a negative-
going V
CC
transient may typically have when issuing a
reset signal. As the amplitude of the transient increas-
es, the maximum allowable pulse width decreases.
GND
GND
Figure 1. Interfacing to µPs with Bidirectional Reset Pins
Table 1. Factory-Trimmed Reset Thresholds
‡
RESET THRESHOLD VOLTAGE, V
TH
(V)
PART
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX632_ _R
MAX634_ _R
MAX634_ _R
MAX634_ _R
MAX634_ _R
MAX634_ _R
MAX634_ _R
SUFFIX
MIN
22
23
24
25
26
27
28
29
30
31
33
34
35
36
37
38
2.167
2.285
2.364
2.462
2.591
2.660
2.758
2.886
2.955
3.034
3.250
3.349
3.447
3.546
3.644
3.743
T
A
= +25°C
TYP
2.200
2.320
2.400
2.500
2.630
2.700
2.800
2.930
3.000
3.080
3.300
3.400
3.500
3.600
3.700
3.800
MAX
2.233
2.355
2.436
2.537
2.669
2.741
2.842
2.974
3.045
3.126
3.350
3.451
3.552
3.654
3.755
3.857
T
A
= -40°C to +85°C
MIN
2.145
2.262
2.340
2.437
2.564
2.633
2.730
2.857
2.925
3.003
3.217
3.315
3.412
3.510
3.607
3.705
MAX
2.250
2.375
2.460
2.562
2.696
2.768
2.870
3.000
3.075
3.150
3.383
3.485
3.587
3.690
3.792
3.895
‡
Factory-trimmed reset thresholds are available in approximately 100mV increments with a 1.5% room-temperature variance.
4
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