Technical Note

10/14

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2010.05 - Rev.A

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BD3506F,BD3506EFV

●

Recommended Circuits

Part No

Value

Notes for use

R1/R2

6.5k/5.5k

The present IC can set output voltage by external reference voltage (VR) and value of output voltage

setting resistors (R1, R2). Output voltage can be set by VRxR2/(R1+R2) but it is recommended to

use at the resistance value (total: about 10 kΩ) which is not susceptible to VREF bias current (±100

nA).

C3

100µF

Connect the output capacitor between Vo1, Vo2 terminals and GND terminal without fail in order to

stabilize output voltage. The output capacitor has a role to compensate for the phase of loop gain

and to reduce output voltage fluctuation when load is rapidly changed. When there is an

insufficient capacity value, there is a possibility to cause oscillation, and when the equivalent serial

resistance (ESR) of the capacitors is large, output voltage fluctuation is increased when load is

rapidly changed. About 100-µF high-performance electrolytic capacitors are recommended but

output capacitor greatly depends on temperature and load conditions. In addition, when only

ceramic capacitors with low ESR are used, or various capacitors are connected in series, the total

phase allowance of loop gain becomes not sufficient, and oscillation may result. Thoroughgoing

confirmation at application temperature and under load range conditions is requested.

C1

0.1µF

The input capacitor plays a part to lower output impedance of a power supply connected to input

terminals (Vcc). When output impedance of this power supply increases, the input voltages (Vcc,)

become unstable and there is a possibility of giving rise to oscillation and degraded ripple rejection

characteristics. The use of capacitors of about 0.1 µF with low ESR, which provide less capacity

value changes caused by temperature changes, is recommended, but since input capacitor greatly

depends on characteristics of the power supply used for input, substrate wiring pattern,

thoroughgoing confirmation under the application temperature and load range, is requested.

C2

10µF

The input capacitor plays a part to lower output impedance of a power supply connected to input

terminals (VIN). When output impedance of this power supply increases, the input voltages (VIN)

become unstable and there is a possibility of giving rise to oscillation and degraded ripple rejection

characteristics. The use of capacitors of about 10 µF with low ESR, which provide less capacity

value changes caused by temperature changes, is recommended, but since input capacitor greatly

depends on characteristics of the power supply used for input, substrate wiring pattern,

thoroughgoing confirmation under the application temperature and load range, is requested.

C4

1µF

To the present IC, there mounted is a function (Non Rush Current on Start-up: NRCS) to prevent

rush current from VIN to load and output capacitor via Vo at the output voltage start-up. When the

EN terminal is reset from High or UVLO, constant current is allowed to flow from the NRCS terminal.

By this current, voltage generated at the NRCS terminal becomes the reference voltage and output

voltage is started. In order to stabilize the NRCS set time, it is recommended to use a capacitor (B

special) with less capacity value change caused by temperature change.

C3

C1

Vcc

+

1

2

3

4

8

7

6

5

C4

R1

C2

VIN

Ven

R2

VOUT(1.2V)/2.5A