BD3509MUV-E2(2009) データシートの表示（PDF） - ROHM Semiconductor
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BD3509MUV-E2 Datasheet PDF : 21 Pages
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BD3508MUV, BD3509MUV
Technical Note
Component
R1/R2
R4
C16
C6
C8
C5
C20
C18
Recommended
Value
3.6k/3.9k
100k
22uF
1uF
10uF
0.1uF
0.01uF
0.01uF
Programming Notes and Precautions
IC output voltage can be set with a configuration formula using the values for the internal
reference output voltage (VFB) and the output voltage resistors (R1, R2).
Select resistance values that will avoid the impact of the VFB current (±100nA). The
recommended total resistance value is 10KΩ.
This is the pull-up resistance for open drain pin. It is recommended to set the value about
100kΩ.
To assure output voltage stability, please be certain the Vo1, Vo2, and Vo3 pins and the GND
pins are connected. 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 47μF 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.
The input capacitor reduces the output impedence of the voltage supply source connected to
the VCC. When the output impedence of this power supply increases, the input voltage
(VCC) may become unstable. This may result in the output voltage oscillation or lowering
ripple rejection. A low ESR 1uF capacitor with minimal susceptibility to temperature is
preferable, but stability depends on power supply characteristics and the substrate wiring
pattern. Please confirm operation across a variety of temperature and load conditions.
Input capacitors reduce the output impedance of the voltage supply source connected to the
(VIN) input pins. If the impedance of this power supply were to increase, input voltage (VIN)
could become unstable, leading to oscillation or lowered ripple rejection function. While a
low-ESR 10uF 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.
Input capacitors reduce the output impedance of the voltage supply source connected to the
(VDD) input pins. If the impedance of this power supply were to increase, input voltage (VDD)
could become unstable, leading to oscillation or lowered ripple rejection function. While a
low-ESR 0.1uF 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.
The Non Rush Current on Startup (NRCS) function is built into the IC to prevent rush current
from going through the load (VIN 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.
This component is employed when the C16 capacitor causes, or may cause, oscillation. It
provides more precise internal phase correction.
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15/20
2009.05 - Rev.A
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