FREQ datasheet(15/56 Pages) FUJITSU

15 / 56 page

MB39A214A

Limitation : development tool vendor use only

FUJITSU SEMICONDUCTOR CONFIDENTIAL

DS405-00007-1v0-E

(4) Starting sequence

When the EN1 pin (pin 2) or EN2 pin (pin 11) is set to the “H” level, the bias voltage is supplied from the

VB pin. If the voltage of the VB pin exceeds the UVLO threshold voltage, the DC/DC converter starts

operations and carries out the soft start. The soft start is a function used to prevent a rush current when the

power is started.

Activating the soft start initiates charging of the capacitor connected to the CS1 pin (pin 5) and CS2 pin (pin

8) and inputs the lamp voltage to the error comparator (Error Comp.) of each channel. The DC/DC

converter generates the output voltage according to that lamp voltage. This results in the soft start operation

that does not depend on the output load. The over voltage protection (OVP) and under voltage protection

(UVP) functions are disabled while the soft start is active.

EN1

CS1

DRVH1

UVLO VTLH

INTREF

0.805 V

1.6 V

0.805 V

DRVL1

VOUT1

EN2

CS2

DRVH2

DRVL2

VOUT2

CH1 soft start completed

UVLO release

CH2 soft start completed

FREQ Datasheet(PDF) 15 Page - fujitsu semiconductor