FREQ datasheet(31/56 Pages) FUJITSU

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MB39A214A

Limitation : development tool vendor use only

FUJITSU SEMICONDUCTOR CONFIDENTIAL

DS405-00007-1v0-E

Power dissipation and the thermal design

IC's loss increases, if IC is used under the high power supply voltage, high switching frequency, high load

and high temperature. The IC internal loss can be calculated by the following formula.

PIC = VCC

(ICC + QG_Total1

fOSC1 + QG_Total2

fOSC2)

PIC

: IC internal loss [W]

VCC

: Power supply voltage (VIN) [V]

ICC

: Power supply current [A] (2 mA Max)

QG_Total1 : Total quantity of charge for the high-side FET and the low-side FET of each CH1 [C]

QG_Total2 : Total quantity of charge for the high-side FET and the low-side FET of each CH2 [C]

fOSC1

: CH1 switching frequency [Hz]

fOSC2

: CH2 switching frequency [Hz]

Calculate junction temperature (Tj) by the following formula.

Tj = Ta

+ θja

PIC

: Junction temperature [°C] (+ 125°C Max)

: Ambient temperature [°C]

θja : TSSOP-24P Package thermal resistance (+ 78°C /W)

PIC

: IC internal loss [W]

Handling of the pins when using a single channel

Although this device is a 2-channel DC/DC converter control IC, it is also able to be used as a 1-channel

DC/DC converter by handling the pins of the unused channel as shown in the following diagram.

Note: x is the unused channel number.

FBx

VOUTx

CSx

ENx

LXx

ILIMx

DRVHx

BSTx

DRVLx

“Open”

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