MB39A136

Document Number: 002-08376 Rev. *A

Page 39 of 50

Power dissipation and the thermal design

As for this IC, considerations of the power dissipation and thermal design are not necessary in most cases because of its high

efficiency. However, they are necessary for the use at the conditions of a high power supply voltage, a high oscillation frequency, high

load, and the high temperature.

Calculate junction temperature (Tj) by the following formula.

Tj

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.

: IC internal loss [W]

: Power supply current [A] (4.7 [mA] Max)

Qg

: All SWFET total quantity of charge for ch 2 [C] (Total with Vgs

: Oscillation frequency[Hz]

Tj

: Junction temperature [°C] (+150 [°C] Max)

Ta

: Ambient temperature [°C]

ja

: TSSOP-24 Package thermal resistance (76°C/W)

: IC internal loss [W]

FBx

CBx

CSx

LXx

ILIMx

CTLx

DRVHx

COMPx

DRVLx

Note: x is the unused channel number.

“Open”

“

“