Datasheet

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 micropro-
cessors (µPs) that have bidirectional reset pins, such as
the Motorola 68HC11. Connecting the µP supervisor’s
RESET output directly to the microcontroller’s (µC’s)
RESET pin with a single pull-up resistor allows either
device to assert reset (Figure 1).
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 increases,
the maximum allowable pulse width decreases.
Figure 1. Interfacing to μPs with Bidirectional Reset Pins
‡Factory-trimmed reset thresholds are available in approximately 100mV increments with a 1.5% room-temperature variance.
Table 1. Factory-Trimmed Reset Thresholds‡
PART SUFFIX
RESET THRESHOLD VOLTAGE, V
TH
(V)
T
A
= +25°C T
A
= -40°C to +85°C
MIN TYP MAX MIN MAX
MAX632_ _R 22 2.167 2.200 2.233 2.145 2.250
MAX632_ _R 23 2.285 2.320 2.355 2.262 2.375
MAX632_ _R 24 2.364 2.400 2.436 2.340 2.460
MAX632_ _R 25 2.462 2.500 2.537 2.437 2.562
MAX632_ _R 26 2.591 2.630 2.669 2.564 2.696
MAX632_ _R 27 2.660 2.700 2.741 2.633 2.768
MAX632_ _R 28 2.758 2.800 2.842 2.730 2.870
MAX632_ _R 29 2.886 2.930 2.974 2.857 3.000
MAX632_ _R 30 2.955 3.000 3.045 2.925 3.075
MAX632_ _R 31 3.034 3.080 3.126 3.003 3.150
MAX634_ _R 33 3.250 3.300 3.350 3.217 3.383
MAX634_ _R 34 3.349 3.400 3.451 3.315 3.485
MAX634_ _R 35 3.447 3.500 3.552 3.412 3.587
MAX634_ _R 36 3.546 3.600 3.654 3.510 3.690
MAX634_ _R 37 3.644 3.700 3.755 3.607 3.792
MAX634_ _R 38 3.743 3.800 3.857 3.705 3.895
RESET
GND
RESET
INPUT
MAX6328
MAX6348
MOTOROLA
68HCXX
µP
GND
V
CC
V
CC
V
CC
MAX6326/MAX6327/
MAX6328/MAX6346/
MAX6347/MAX6348
3-Pin, Ultra-Low-Power SC70/SOT
μP Reset Circuits
www.maximintegrated.com
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