3-Pin, Ultra-Low-Power SC70/SOT
µP Reset Circuits
____________ Applications Information
V
CC
Interfacing to µPs with
Bidirectional Reset Pins
V
V
CC
CC
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).
µP
MAX6328
MAX6348
MOTOROLA
68HCXX
RESET
INPUT
RESET
Negative-Going V
Transients
CC
GND
GND
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
transients (glitches).
CC
Figure 1. Interfacing to µPs with Bidirectional Reset Pins
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
transient may typically have when issuing a
CC
reset signal. As the amplitude of the transient increas-
es, the maximum allowable pulse width decreases.
‡
Table 1. Factory-Trimmed Reset Thresholds
RESET THRESHOLD VOLTAGE, V (V)
TH
PART
SUFFIX
T
A
= +25°C
T = -40°C to +85°C
A
MIN
TYP
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
MIN
MAX
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
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
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
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
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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