BD3509MUV データシートの表示（PDF） - ROHM Semiconductor

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BD3509MUV

Nch FET Ultra LDO for PC Chipsets with Power Good

ROHM Semiconductor 

BD3508MUV,BD3509MUV

Technical Note

Component

R1/R2

R4

C16

C6

C8

C5

C20

C18

Recommended

Value

3.6k / 3.9k

100k

22µF

1µF

10µF

0.1µF

0.01µF

0.01µF

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 1µF 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 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.

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 0.1µF 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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2010.04 - Rev.C

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