Datasheet
LTC4000-1
29
40001fa
For more information www.linear.com/LTC4001-1
applicaTions inForMaTion
DESIGN EXAMPLE
In this design example, the LTC4000-1 is paired with the
LT3845A buck converter to create a 10A, 3-cell LiFePO
4
battery charger. The circuit is shown on the front page
and is repeated here in Figure 22.
• With R
IFB2
set at 20k, the input voltage monitoring falling
threshold is set at 15V and the input voltage regulation
level is set at 17.6V according to the following formulas:
R
VM3
= 1−
1.193V
15V
17.6V
1V
20kΩ = 324kΩ
R
VM4
= 1.193V
17.6V
15V
−1
20kΩ = 8.06kΩ
• The input current sense resistor is set at 5mΩ. There-
fore, the voltage at the IIMON pin is related to the input
current according to the following formula:
V
IIMON
= (0.1Ω) • I
RIS
• R
CL
is set at 24.9kΩ such that the voltage at the CL pin
is 1.25V. Similar to the IIMON pin, the regulation voltage
on the IBMON pin is clamped at 1V with an accurate
internal reference. Therefore, the charge current limit
is set at 10A according to the following formula:
I
CLIM(MAX)
=
0.050V
R
CS
=
0.050V
5mΩ
= 10A
• The trickle charge current level is consequently set at
1.25A, according to the following formula:
I
CLIM(TRKL)
= 0.25µA •
24.9k
Ω
5mΩ
= 1.25A
• The battery float voltage is set at 10.8V according to
the following formula:
R
BFB1
=
10.8
1.136
−1
• 133kΩ ≈ 1.13MΩ
Figure 22. 10.8V at 10A Charger for Three LiFePO
4
Cells with Solar Panel Input
1.13M
14.7k
127k
10k
10k
3-CELL Li-Ion
BATTERY PACK
V
BAT
10.8V FLOAT
10A MAX CHARGE
CURRENT
NTHS0603
N02N1002J
1.15M
47nF
5mΩ
V
OUT
12V, 15A
SOLAR PANEL INPUT
<60V OPEN CIRCUIT VOLTAGE
17.6V PEAK POWER VOLTAGE
133k
CSN
CSP
BGATE
IGATE
BAT
OFB
FBG
BFB
NTC
CX
LTC4000-1
ITH CC IID
5mΩ
LT3845A
100µF
OUT
V
C
SHDN
IN
RST
CLN
IN
ENC
CHRG
F LT
VM
22.1k
CLTMRIIMON IBMON
BIAS
GND BIAS
BIAS
24.9k
1µF
324k
8.06k
IFB
20k
1µF10nF
40001 F22
Si7135DP
Si7135DP
3.0V
1M
0.1µF
10nF
10M