Datasheet

MAX6800/MAX6801/MAX6802
3-Pin, Low-Power
µP Reset Circuits
4 _______________________________________________________________________________________
V
CC
V
CC
GND
MAX6802
RESET
V
CC
GND
RESET
MOTOROLA
68HCXX
µP
100kΩ
Applications Information
Interfacing to µPs with Bidirectional
Reset Pins
Since the RESET output on the MAX6802 is open-drain,
this device interfaces easily with µPs that have bidirec-
tional 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
pullup 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 Maximum Transient Duration vs. Reset
Comparator Overdrive graph. The graph shows the maxi-
mum pulse width that a negative-going V
CC
transient may
typically have without issuing a reset signal. As the ampli-
tude of the transient increases, the maximum allowable
pulse width decreases.
Figure 1. Interfacing to µPs with Bidirectional Reset Pins
TOP VIEW
1
2
3
V
CC
RESET (RESET)
MAX6800
MAX6801
MAX6802
SOT23-3
( ) ARE FOR MAX6800
GND
Pin Configuration
Figure 2. Ensuring Reset Valid Down to V
CC
= 0V
V
CC
GND
MAX6801
RESET
100kΩ
(a)
V
CC
GND
MAX6800
RESET
100kΩ*
(b)
*ASSUMES HIGH-Z RESET INPUT TO THE µP
MAX6801
V
CC
V
CC
RESET
RESET
GND
V
CC
GND
µP
Typical Operating Circuit