Datasheet

MAX690T/S/R, 704T/S/R, 802T/S/R, 804–806T/S/R
3.0V/3.3V Microprocessor Supervisory Circuits
10 ______________________________________________________________________________________
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
V
CC
GND
0V
TO μP
V
L
= R
1
V
PFT
PFI
PFO
R
1
R
2
R
3
*OPTIONAL
C1*
V
IN
V
TRIP
V
IN
PFO
0V
V
H
V
L
R
1
+ R
2
R
2
V
H
= (V
PFT
+ V
PFH
) (R
1
)
V
TRIP
= V
PFT
+
R
1
1
+
R
2
1
R
3
1
–
R
3
V
CC
V
PFT
= 1.237V
V
PFH
= 10mV
WHERE
V
CC
GND
TO μP
PFI
PFO
R
1
R
2
R
3
*OPTIONAL
C1*
V
IN
R
1
+ R
2
R
2
V
H
= R
1
(V
PFT
+ V
PFH
)
V
TRIP
= V
PFT
+
R
1
1
+
R
2
1
R
3
1
–
R
3
(V
CC -
V
D
)
V
PFT
= 1.237V
V
PFH
= 10mV
V
D
= DIODE FORWARD VOLTAGE DROP
V
L
= V
TRIP
WHERE
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
0V
PFO
0V
V
H
V
IN
V
TRIP
ba
( )
( )
( )
( )
+
R
1
1
+
R
2
1
R
3
1
( )
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
V
CC
GND
PFI PFO
R
1
R
2
V-
0V
V-
PFO
V
TRIP
V
L
V
PFT
= 1.237V
V
PFH
= 10mV
WHERE
3.0V OR 3.3V
V
TRIP
= R
2
+
R
1
1
)
(
R
2
1
–
R
1
V
CC
(V
PFT
+ V
PFH
)
V
L
= R
2
+
R
1
1
)
(
R
2
1
–
R
1
V
CC
(V
PFT
)
NOTE: V
TRIP
IS NEGATIVE
V
CC
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
V
CC
GND
PFI PFO
R
1
R
2
PFO
V
TRIP
V
H
* MAX704T/S/R,
MAX806T/S/R ONLY
3.0V OR 3.3V
V
IN
V
TRIP
=
)
(
R
2
R
1
+ R
2
V
PFT
V
H
= (V
PFT
+ V
PFH
)
V
CC
V
IN
MR
*
ba
)
(
R
2
R
1
+ R
2
Figure 4. a) Adding Additional Hysteresis to the Power-Fail Comparator b) Shifting the Additional Hysteresis above V
PFT
Figure 5. Using the Power-Fail Comparator to Monitor an Additional Power Supply