Datasheet

MAX705–MAX708/MAX813L
Interfacing to µPs with
Bidirectional Reset Pins
µPs with bidirectional reset pins, such as the Motorola
68HC11 series, can contend with the MAX705-MAX708
RESET
output. If, for example, the RESET output is driven
high and the µP wants to pull it low, indeterminate logic
levels may result. To correct this, connect a 4.7kΩ
resistor between the RESET output and the µP reset I/O,
as in Figure 8. Buffer the RESET
output to other system
components.
Low-Cost, µP Supervisory Circuits
8 _______________________________________________________________________________________
MAX70_
RESET
R2
R1
+5V
V-
V
CC
PFI
GND
MR
PFO
TO µP
100k
100k
2N3904
MR
PFO
+5V
0V
+5V
0V
V
TRIP 0V
V-
Figure 7. Monitoring a Negative Voltage
MAX70_
BUFFERED RESET TO OTHER SYSTEM COMPONENTS
4.7k
V
CC
GND
RESET
V
CC
GND
RESET
µP
Figure 8. Interfacing to µPs with Bidirectional Reset I/O
5 1.25
R1
1.25 V
TRIP
R2
,V
TRIP
0
−
=
−
<
MAX70_
RESET
R1
Figure 5. RESET Valid to Ground Circuit
MAX70_
RESET
130k
1%
PARAMETER
MIN TYP
MAX UNIT
+12V Reset
Threshold at +25°C
10.67
10.87
11.50 V
1M
1%
+5V
+12V
V
CC
PFI
GND
MR
PFO
TO µP
Figure 6. Monitoring Both +5V and +12V