FA7764 データシートの表示（PDF） - Fuji Electric

部品番号

コンポーネント説明

メーカー

FA7764

DC/DC Power Supply control IC

Fuji Electric 

FA7764

(13) VBIAS circuit

This IC provides the VBIAS pin to increase the

efficiency of the power supply circuit and reduce the

IC power loss.

The internal regulated power supply CREG is

usually generated by the VCC voltage.

If CREG is generated from the output voltage of the

DC-DC converter by the VBIAS pin, it is able to

reduce the power loss at CREG regulator and lower

power consumption operation (Fig. 5).

Fig. 5

When the VBIAS pin is not used, the operating

current consumption of the VCC terminal is 0.75 mA

(typ), on the other hand, when the VBIAS pin is used,

the comparable consumption is 0.4 mA(typ).

This operation switchover is performed at the

VBIAS pin voltage (i.e., output voltage of the DC-DC

converter) of 3.1V. Therefore, the VBIAS operation

will be effective only at the input voltage more than

3.1V.

Furthermore, a 5.5 V Zener diode for protection is

connected to the VBIAS pin. Therefore, if more than

5.5V voltage is applied to the VBIAS pin, a leak

current will be occurred in the Zener diode and also

increases the power loss.

Therefore, apply the voltage from 3.1V to 5.5V to

the VBIAS pin when you use the VBIAS pin function.

Connect a ceramic capacitor close to the VBIAS

pin as shown in Fig. 5 to eliminate noise. The

recommended value of the capacitance is about 0.1

μF.

If you do not use the VBIAS pin and in case of set

the DC-DC converter output voltage to less than

3.1V or more than 5.5V, connect the VBIAS pin to

the GND (Fig. 6).

Fig. 6

Fuji Electric Systems Co., Ltd.

AN-059E Rev.1.0

14

June.2010

http://www.fujielectric.co.jp/fdt/scd/

Share Link: