Technical Note

2012.03 - Rev.C

© 2012 ROHM Co., Ltd. All rights reserved.

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10/18

BD9006F/HFP, BD9007F/HFP, BD9009HFP

●External synchronizing function

In order to activate the external synchronizing function, connect the frequency setting resistor to the RT pin and then input a

synchronizing signal to the EN/SYNC pin. As the synchronizing signal, input a pulse wave higher than a frequency

determined with the setting resistor (RT).

However, the external sync frequency should be configured at less than double the configured frequency.

(ex.) When the configured frequency is 100kHz, the external sync frequency should be less than 200kHz.

Furthermore, the pulse wave’s LOW voltage should be under 0.8V and the HIGH voltage over 2.6V (when the HIGH voltage

is over 6V the EN/SYNC input current increases [see p.4 Fig.8]), the through rate of stand-up (and stand-down) under 20V/

μS.

Fig.35 External Sync Sample Circuit

(Vo=3.3V, Io=1A, f=300kHz, EN/SYNC=450kHz)

220μF

C28

2μF

SW

33μH

L1

C0

330μF

D1

47kΩ

R1

15kΩ

R2

GND

GND

GND

C3

open

R3

30kΩ

REG

C2

open

C1

22000pF

51kΩ

BD9006HFP

BD9007HFP

BD9009HFP

Ven/sync=0～5V

f=450kHz

SR =20V/μ s

Duty=50%