BD3523HFN, BD35230HFN, BD35231HFN
Technical Note
16/20
www.rohm.com
2009.04 - Rev.B
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●Recommended Circuit Example (BD35230HFN/BD35231HFN)
Component
Recommended
Value
Programming Notes and Precautions
C3 22μF
To assure output voltage stability, please be certain the output capacitors are connected
between Vo pin and GND. Output capacitors play a role in loop gain phase compensation
and in mitigating output fluctuation during rapid changes in load level. Insufficient
capacitance may cause oscillation, while high equivalent series reisistance (ESR) will
exacerbate output voltage fluctuation under rapid load change conditions. While a 22μF
ceramic capacitor is recomended, actual stability is highly dependent on temperature and
load conditions. Also, note that connecting different types of capacitors in series may result in
insufficient total phase compensation, thus causing oscillation. In light of this information,
please confirm operation across a variety of temperature and load conditions.
C1/C2 1μF/10μF
Input capacitors reduce the output impedance of the voltage supply source connected to the
(V
CC, VIN) input pins. If the impedance of this power supply were to increase, input voltage
(VCC, VIN) could become unstable, leading to oscillation or lowered ripple rejection function.
While a low-ESR 1μF/10μF capacitor with minimal susceptibility to temperature is
recommended, stability is highly dependent on the input power supply characteristics and the
substrate wiring pattern. In light of this information, please confirm operation across a variety
of temperature and load conditions.
C4 0.01μF
The Non Rush Current on Startup (NRCS) function is built into the IC to prevent rush current
from going through the load (V
IN to VO) and impacting output capacitors at power supply
start-up. Constant current comes from the NRCS pin when EN is HIGH or the UVLO function
is deactivated. The temporary reference voltage is proportionate to time, due to the current
charge of the NRCS pin capacitor, and output voltage start-up is proportionate to this
reference voltage. Capacitors with low susceptibility to temperature are recommended, in
order to assure a stable soft-start time.
C5 1000pF
This component is employed when the C16 capacitor causes, or may cause, oscillation. It
provides more precise internal phase correction.
6
V
cc
EN
VIN
4
3
2
1
V
o
V
o
8
7
6
5
GND
FB
NRCS
C1
V
cc
R4
EN
C4
VIN
C2
C3
GND
FB
V
o
C5