MAX704R Maxim Integrated Products, MAX704R Datasheet - Page 10

• Manufacturer Part Number: MAX704R
• Description: P Reset ic With Watchdog And Battery Switchover
• Manufacturer: Maxim Integrated Products

3.0V/3.3V Microprocessor Supervisory Circuits
Figure 4. a) Adding Additional Hysteresis to the Power-Fail Comparator
Figure 5. Using the Power-Fail Comparator to Monitor an Additional Power Supply
10
a
a
______________________________________________________________________________________
PFO
V
V
TRIP
CC
V
L
PFO
= R
= R
R
R
R
R
V
0V
V
2
2
1
2
V
1
2
TRIP
H
L
(V
V
= (V
V-
(V
= R
0V
IN
PFT
PFT
= V
1
PFT
PFT
+ V
)
V
(
PFT
+ V
PFH
1
R
(
1
R
PFH
C1*
1
+
)
(
+ R
R
(
1
R
2
) (R
1
R
TO P
1
1
R
2
2
+
1
1
)
)
)
+
1
R
–
R
(
PFI
2
3
1
R
1
R
V
+
2
1
V
CC
R
V
1
L
+
L
)
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
1
R
PFI
PFO
3
–
1
R
)
2
V
V
CC
R
TRIP
–
+
V
V
GND
1
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
TRIP
CC
V
1
R
CC
R
3
3
3.0V OR 3.3V
)
GND
V
CC
V
WHERE
H
WHERE
NOTE: V
PFO
0V
V
V
PFT
PFH
TRIP
V
V
*OPTIONAL
PFT
PFH
= 1.237V
= 10mV
IS NEGATIVE
= 1.237V
= 10mV
V
IN
V-
b
b
b) Shifting the Additional Hysteresis above V
PFO
V
CC
V
V
TRIP
H
= (V
PFO
V
R
R
V
=
TRIP
1
2
WHERE
R
R
H
0V
PFT
1
2
V
V
= R
IN
PFT
V
= V
+ V
0V
IN
1
PFT
(
(V
V
V
PFH
R
PFT
PFH
PFT
1
V
V
R
D
(
L
+ R
)
R
2
(
1
+ V
= 1.237V
= 10mV
= DIODE FORWARD VOLTAGE DROP
= V
2
R
R
+ R
C1*
1
2
)
TRIP
PFH
R
+ R
2
2
TO P
)
)
2
V
(
TRIP
PFI
)
R
1
R
3
1
V
+
TRIP
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
1
R
PFI
PFO
V
2
H
+
GND
V
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
CC
1
R
3
3.0V OR 3.3V
)
V
GND
–
CC
V
(V
H
* MAX704T/S/R,
CC -
MAX806T/S/R ONLY
PFO
MR
R
3
V
D
PFT
)
*OPTIONAL
*
V
V
IN
IN