MAX705–MAX708/MAX813L
Low-Cost, µP Supervisory Circuits
+5V
+12V
V
CC
TO µP
RESET
1MΩ
1%
MAX70_
MAX70_
MR
130kΩ
1%
RESET
PFI
PFO
GND
R1
PARAMETER
MIN TYP MAX UNIT
10.67 10.87 11.50
+12V Reset
Threshold at +25°C
V
Figure 5. RESET Valid to Ground Circuit
Figure 6. Monitoring Both +5V and +12V
+5V
BUFFERED RESET TO OTHER SYSTEM COMPONENTS
100kΩ
V
CC
MR
R1
R2
MAX70_
100kΩ
V
V
CC
CC
PFO
2N3904
PFI
MAX70_
µP
4.7kΩ
RESET
RESET
RESET
TO µP
GND
V-
MR
GND
GND
+5V
0V
+5V
0V
PFO
Figure 8. Interfacing to µPs with Bidirectional Reset I/O
V
TRIP
V-
0V
Interfacing to µPs with
Bidirectional Reset Pins
1.25 − V
5 −1.25
TRIP
=
,V
< 0
TRIP
R1
R2
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.
Figure 7. Monitoring a Negative Voltage
8
Maxim Integrated
ROCHESTER [ Rochester Electronics ]
