LTC3789 LINER [Linear Technology], LTC3789 Datasheet - Page 30

• Manufacturer Part Number: LTC3789
• Description: High Voltage High Current Controller for Battery Charging and Power Management
• Manufacturer: LINER [Linear Technology]

applicaTions inForMaTion
LTC4000
This same procedure is then repeated for the other four
loops: the input current regulation, the output voltage
regulation, the battery float voltage regulation and finally
the charge current regulation when V
Note that the resulting optimum values for each of the loops
may differ slightly. The final values of C
selected by combining the results and ensuring the most
conservative response for all the loops. This usually entails
picking the largest value of C
R
particular example, the value of C
and R
BOARD LAYOUT CONSIDERATIONS
In the majority of applications, the most important param-
eter of the system is the battery float voltage. Therefore,
the user needs to be extra careful when placing and routing
the feedback resistor R
battery sense line connected to R
line for the LTC4000 must be Kelvined back to where the
battery output and the battery ground are located respec-
tively. Figure 19 shows this Kelvin sense configuration.
30
C
based on the results obtained for all the loops. In this
C
= 14.7kΩ.
BFB1
and R
C
and the smallest value of
BFB1
C
BFB2
Figure 19. Kelvin Sense Lines Configuration for LTC4000
R
and the ground return
is finally set to 47nF
IS
V
OFB
IN
GND
CONVERTER
SWITCHING
. In particular, the
C
> V
and R
CLN
IN
ITH
ITH
OUT(INST_ON)
C
are then
R
C
LTC4000
GND
CC
C
C
.
IID
BGATE
IGATE
For accurate current sensing, the sense lines from R
and R
to the sense resistors terminals. The two sense lines of
each resistor must also be routed close together and away
from noise sources to minimize error. Furthermore, cur-
rent filtering capacitors should be placed strategically to
ensure that very little AC current is flowing through these
sense resistors as mentioned in the applications section.
The decoupling capacitors C
as close to the LTC4000 as possible. This allows as short
a route as possible from C
well as from C
In a typical application, the LTC4000 is paired with an
external DC/DC converter. The operation of this converter
often involves high dV/dt switching voltage as well as high
currents. Isolate these switching voltages and currents
from the LTC4000 section of the board as much as pos-
sible by using good board layout practices. These include
separating noisy power and signal grounds, having a good
low impedance ground plane, shielding whenever neces-
sary, and routing sensitive signals as short as possible
and away from noisy sections of the board.
CSN
CSP
FBG
BAT
BFB
CS
R
R
BFB1
BFB2
(Figure 19) must be Kelvined back all the way
R
BIAS
4000 F19
CS
SYSTEM LOAD
to the BIAS and GND pins.
IN
IN
to the IN and GND pins, as
and C
BIAS
must be placed
4000f
IS