BD9528 View Datasheet(PDF) - ROHM Semiconductor

Part Name

Description

Manufacturer

BD9528

Main Power Supply for Notebook PCs

ROHM Semiconductor 

BD9528AMUV

Technical Note

8. Relation between output voltage and frequency

Because the BD9528AMUV is TON time focused regulator controller, if output current is up, switching loss of Coil,

MOSFET and output capacitor will increase, and frequency will be fast.

Loss of each Coil, MOSFET and output capacitor are below.

① Coil loss = IOUT2 × DCR

② MOSFET(High Side) loss = IOUT2 × Ronh ×

VOUT

VIN

③ MOSFET(Low Side) loss = IOUT2 × RonL × (1-

VOUT )

VIN

(Ronh : ON resistance of high side MOSFET, Ronl : ON resistance of low side MOSFET,

ESR : Output capacitor equivalent cascade resistance)

Regarding those loss above and frequency formula, it is determined below.

T (=1/Freq) =

VIN × IOUT × Ton

VOUT × IOUT + ① + ② + ③

・・・(17)

However, real-life considerations (such as parasitic resistance element of Layout pattern) must be factored in as they

affect the loss, please confirm in reality by the instrument.

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© 2011 ROHM Co., Ltd. All rights reserved.

21/29

2011.11 - Rev.A

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