Manual

MAX16033–MAX16040
Low-Power Battery Backup
Circuits in Small µDFN Packages
14 ______________________________________________________________________________________
GND
TO µP
PFI
R2
C1 C1
R3 R3
R1
PFO (PUSH-PULL)
MAX16033–
MAX16040
V
CC
V
IN
PFO
GND
TO µP
PFI
R2
R1
PFO (PUSH-PULL)
MAX16033–
MAX16040
V
CC
V
IN
0V
V
L
V
H
V
H
V
IN
V
TRIP
V
TRIP
PFO
0V
V
IN
(a) (b)
Figure 8. (a) Adding Additional Hysteresis to the Power-Fail Comparator. (b) Shifting the Additional Hysteresis above V
TRIP
VV
R
R
VV V
R
R
R
R
VV
R
R
R
R
R
R
V
VV
VmV
TRIP PFT
H PFT PFH
L PFT CC
PFT
PFH
( )
.
=+
⎛
⎝
⎜
⎞
⎠
⎟
=+ ++
⎛
⎝
⎜
⎞
⎠
⎟
=++
⎛
⎝
⎜
⎞
⎠
⎟
−
=
=
1
1
2
1
1
2
1
3
1
1
2
1
3
1
3
1 235
12
VV
R
R
VV V
R
R
R
R
R
R
V
VV
VV
VmV
V DIODE FORWARD VOLTAGE
TRIP PFT
H PFT PFH D
L TRIP
PFT
PFH
D
( )
.
=+
⎛
⎝
⎜
⎞
⎠
⎟
=+ ++
⎛
⎝
⎜
⎞
⎠
⎟
−
=
=
=
=
1
1
2
1
1
2
1
3
1
3
1 235
12