LTC3789 LINER [Linear Technology], LTC3789 Datasheet - Page 29

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

applicaTions inForMaTion
Figure 16. Transient Response of Charge Current Regulation Loop
Observed at IBMON When V
C
The transient response shows a small overshoot with slow
settling indicating a fast minor loop within a well damped
overall loop. Therefore, the value of C
tively until C
loop with C
Figure 17. Transient Response of Charge Current Regulation Loop
Observed at IBMON When V
C
C
C
= 1µF , R
With C
regulated at 9.8V and a 0.2A output load condition at
CSP , the transient response for a 100mA charge current
step observed at IBMON is shown in Figure 16.
= 22nF , R
–10
–15
15
10
–5
5
0
–10
–15
–20
C
C
15
10
–5
C
5
0
= 10k for a 100mA Charge Current Step
= 1µF , R
C
–20
C
= 10k for a 100mA Charge Current Step
= 22nF and R
–15
= 22nF . The transient response of the same
–15
–10
–10
C
= 10k at V
–5
–5
OFB
OFB
5ms/DIV
0
C
5ms/DIV
is Regulated to V
0
is Regulated to V
= 10k is shown in Figure 17.
5
IN
5
10
= 20V, V
10
15
C
15
is reduced itera-
20
BAT
4000 F16
OUT(INST_ON)
OUT(INST_ON)
20
4000 F17
25
= 7V, V
25
CSP
with
with
The transient response now indicates an overall under
damped system. As noted in the empirical loop compensa-
tion section, the value of R
until R
with C
Figure 18. Transient Response of Charge Current Regulation Loop
Observed at IBMON When V
C
Note that the transient response is close to optimum
with some overshoot and fast settling. If after iteratively
increasing the value of R
indicates an over damped system, the step of reducing
C
by increasing R
arrives at a stable loop with the smallest value of C
the largest value of R
values are found to be C
After arriving at these final values of R
margin is checked by varying the values of both R
C
the setup condition is varied, including varying the input
voltage level and the output load level and the transient
response is checked at these different setup conditions.
Once the desired responses on all different conditions are
obtained, the values of R
C
C
C
= 22nF , R
can be repeated. These steps of reducing C
by 2:1 in all four possible combinations. After which
C
C
= 22nF and R
= 20k. The transient response of the same loop
–10
–15
15
10
–5
5
0
–20
C
= 20k for a 100mA Charge Current Step
–15
C
can be repeated continuously until one
–10
C
C
–5
. In this particular example, these
= 20k is shown in Figure 18.
OFB
C
C
C
= 22nF and R
5ms/DIV
, the transient response again
and C
0
C
is Regulated to V
is now increased iteratively
5
C
10
are noted.
C
and C
15
LTC4000
C
= 20kΩ.
20
OUT(INST_ON)
C
4000 F18
, the stability
25
C
followed
29
C
C
and
and
4000f
with