Datasheet

Evaluation Board User Guide UG-310
Rev. 0 | Page 5 of 12
Changing the Soft Start Time
The top resistor, R4 (R18 for Channel 2), value is calculated using
the following equations:
The soft start time of the ADP2323 on the evaluation board is
programmed to 1.7 ms.
For Channel 1,
R4 = R7 ×
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
V0.6
V0.6
OUT1
V
To change the soft start time, t
SS
, replace the C6 capacitor for
Channel 1 (C21 for Channel 2) with a different capacitor value
using the following equation:
For Channel 2,
For Channel 1,
R18 = R17 ×
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
V0.6
V0.6
2OUT
V
C6 [nF] = 5.83 × t
SS
[ms]
For Channel 2,
When the output voltage of Channel 1 is changed, the values
of the inductor (L1), the output capacitors (C8, C9, and C10),
and the compensation components (R5, C4, and C5) must be
recalculated and changed to ensure stable operation (see the
ADP2323 data sheet for details on external component selection).
Likewise, if the output voltage of Channel 2 is changed, the values
of the inductor (L2), the output capacitors (C15, C16, and C17),
and the compensation components (R19, C20, and C19) must
be recalculated and changed.
C21 [nF] = 5.83 × t
SS
[ms]
Changing the Peak Current-Limit Threshold
The peak current-limit threshold of the ADP2323 evaluation
board is set to 4.8 A.
To change the peak current-limit threshold, replace the R9 resistor
for Channel 1 (R14 for Channel 2) with a different resistor value,
as shown in Table 3. The programmable current-limit threshold
feature allows for the use of a small size inductor for low current
applications.
Changing the Switching Frequency
The switching frequency (f
SW
) set point can be changed by
replacing the R13 resistor with a different value, as shown in
the following equation:
Table 3. Peak Current-Limit Threshold Setting
R9/R14 Peak Current-Limit Threshold (A)
Open 4.8
47 kΩ 3
15 kΩ 1.5
f
SW
[kHz] = 60, 000/R13 [kΩ]
A 200 kΩ resistor sets the frequency to 300 kHz, and a 100 kΩ
resistor sets the frequency to 600 kHz.
When the switching frequency is changed, the values of the
inductor (L1 and L2), the output capacitors (C8, C9, C10 and
C15, C16, C17), the compensation networks (R5, C4, C5 and
R19, C20, C19) must be recalculated and changed for stable
operation (see the ADP2323 data sheet for details on external
component selection).