Rainbow Electronics MAX16040 - Manual (Page 14)

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
V V
R
R
V V V
R
R
R
R
V V
R
R
R
R
R
R
V
V V
V mV
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
V V
R
R
V V V
R
R
R
R
R
R
V
V V
V V
V mV
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