LTC4110EUHF LINER [Linear Technology], LTC4110EUHF Datasheet - Page 39

• Manufacturer Part Number: LTC4110EUHF
• Description: Battery Backup System Manager
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
R1 = resistor connected between DCDIV and GND
R2 = resistor connected between supply input and
DCDIV
V
For example, if supply input = 12V and backup starts when
it drops to 11V, then V
R2/R1 = 8.02, choose R1 = 10k, then R2 = 80.6k.
If a higher ratio than V
V
shown in Figure 17.
where:
V
such as SMBus pull up, LED supply or LTC4110’s V
voltage, must be higher than 1.7V. R3 = resistor connected
between V
BGR
BACKDRIVE
DC
V
OPTIONAL RESISTOR
DC
TO INCREASE THE
R
R
R
V
R
V
1.23 TO 1 RATIO
= Any regulated DC voltage available in the system
2
BACKDRIVE
3
BACKDRIVE
1
1
= reference voltage 1.220V
Figure 17. Backup and Boost Detect Comparators
=
=
R3
V
V
V
DC
BACKDRIVE
BGR
DC
and V
0 23
0 23
and DCDIV.
.
.
0 23
•
– – .
– .
SUPPLY
.
INPUT
V
BACKUP
1 23
1 23
BACKDRIVE
•
•
R2
R1
V
V
•
V
OVP
DC
D D C
BACKD
–
V
BACKUP
BGR
•
•
DCDIV
V
, a third resistor can be used as
/V
V
V
BACKUP
1.23 • V
BACKUP
BACKUP
BGR
R R IVE
= 11V, V
– .
V
BGR
BGR
= 1.23 is desired between
1 23
–
−
−
−
V
–
+
+
–
BACKUP
1
1
•
BACKDRIVE
CMP
CMP
V
BACKUP
= 13.5V,
−
BACKUP
BOOST
4110 F17
DD
For example, if supply input = 12V and backup starts when
it drops to 8V, calibration terminates when it rises to 16V,
and V
choose R1 = 10k then R2 = 221k and R3 = 39.2k.
If the noise on supply input is a problem, a capacitor can
be connected between DCDIV and GND.
PROGRAMMING CALIBRATION/BACKUP CUT-OFF
THRESHOLD
The pins V
discharge cut-off voltages for their respective operating
modes. The equations shown below are generic for both.
There is no implied relationship between V
for they are independent of each other.
The equations are most helpful if you pick the V
voltage you want, within the range limits offered, and then
solve for V
V
network from V
on these pins respectively. It is recommended that one
single series resistor divider network from V
be used to obtain all of the pin voltages you need. It should
be noted that custom values of V
divider network complexity. See Programming Charge
Voltage section for more information.
Connect the V
calibration/backup cut-off threshold (2.75V for Li-Ion,
1.93V for SLA, 0.95V for NiMH/NiCd). These threshold
voltages can be adjusted (±400mV for Li-Ion, ±300mV
for SLA, ±200mV for NiMH/NiCd) by tying the pin to ap-
propriate voltage on the V
to the following equations:
DIS
V
V
V
CUTOFF
CUTOFF
CUTOFF
calculated, determine the necessary voltage divider
DC
= V
CAL
DD
CAL
=
=
=
CAL
= 4.75V, then R2/R1 = 21.87, R3/R1 = 3.88,
or V
V
V
V
REF
and V
CAL
C
CAL
A A L
or V
V
V
V
DIS
required to get the calculated voltage
BGR
BGR
BGR
/
/
/
DIS
. With the voltage value of V
V
V
V
DIS
DIS
DIS
DIS
REF
are used to calculate custom
pin to GND will set the default
• .
• .
• •
pin resistor divider according
4 2
2 35
2
CHG
(
NiMH NiCD
(
Li Ion
would also affect the
(
SLA
−
LTC4110
/
)
REF
CAL
)
to ground
)
and V
39
CUTOFF
CAL
4110fa
DIS
or