Technical Note

5/17

BU6650NUX, BU6651NUX, BU6652NUX, BU6653NUX

www.rohm.com

2009.09 - Rev.B

© 2009 ROHM Co., Ltd. All rights reserved.

Fig.5 Stability area characteristics (Example)

0.01

0.1

1

10

100

0

50

100

150

200

IOUT [mA]

Stability area

Unstable area

Capacity value of ceramic capacitor - DC bias characteristics

(

Example)

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

00.5

1

1.5

22.53

3.54

DC Bias Voltage [V]

10-V withstand voltage

B1characteristics

GRM188B11A105KA61D

10-V withstand voltage

B characteristics

6.3-V withstand voltage

B characteristics

4-V withstand voltage

X6S characteristics

10-V withstand voltage

F characteristics

10-V withstand voltage

F characteristics



Input/Output terminal equivalent circuit schematic

6,7,8pin (VOUT)

5pin (GND)

2,3,4pin (STBY)

1pin (VIN)

STBY

Fig.3 Input/Output equivalent circuit



About input/output capacitor

It is recommended to place a capacitor as close as possible to the pins

between the input terminal and GND or between the output terminal and

GND.

The capacitor between the input terminal and GND becomes valid when

source impedance increases or when wiring is long. The larger the

capacity of the output capacitor between the output terminal and GND is,

the better the stability and characteristics in output load fluctuation

become. However, please check the status of actual implementation.

Ceramic capacitors generally have variation, temperature characteristics,

and direct current bias characteristics and the capacity value also

decreases with time depending on the usage conditions. It is

recommended to select a ceramic capacitor upon inquiring about

detailed data of the related manufacturer.



About the equivalent series resistance (ESR) of a ceramic capacitor

Capacitors generally have ESR (equivalent series resistance) and it

operates stably in the ESR-IOUT area shown on the right. Since

ceramic capacitors, tantalum capacitors, electrolytic capacitors, etc.

generally have different ESR, please check the ESR of the capacitor

to be used and use it within the stability area range shown in the

right graph for evaluation of the actual application.

VOUT

Fig.4 Capacity – bias characteristics