MB39A110 View Datasheet(PDF) - Fujitsu

Part Name

Description

Manufacturer

MB39A110

4-ch DC/DC Converter IC with Synchronous Rectification

Fujitsu 

MB39A110

■ SETTING THE DEAD TIME

When the device is set for step-up or inverted output based on the step-up or step-up/down Zeta conversion,

step-up/down Sepic conversion or flyback conversion, the FB terminal voltage may reach and exceed the trian-

gular wave voltage due to load fluctuation. If this case happens, the output transistor is fixed to a full-ON state

(ON duty = 100 %). To prevent this, set the maximum duty of the output transistor. To set it, set the voltage at

the DTC terminal by applying a resistive voltage divider to the VREF voltage as shown below.

When the DTC terminal voltage is higher than the triangular wave voltage, the output transistor is turned on.

The maximum duty calculation formula assuming that triangular wave amplitude = 0.5 V and triangular wave

lower voltage = =: 0.4 V is given below.

DUTY (ON) Max =

Vdt − 0.4 V

0.5 V

× 100 (%) , Vdt =

Rb

Ra + Rb

× VREF

When the DTC terminal is not used, connect it directly to the VREF terminal (pin 11) as shown below (when no

dead time is set).

• When using DTC to set dead time

11 VREF

DTCX

Ra

Rb

Vdt

• When no dead time is set

11 VREF

X: Each channel No.

DTCX

X: Each channel No.

20

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