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LT3840

3840fa

For more information www.linear.com/LT3840

operaTion

and current limited. Figure 3 is a functional block diagram

of the auxiliary bias supply.

Auxiliary Bias Supply Start-Up and Shutdown

The LT3840 auxiliary bias supply is enabled with the en-

able (EN) pin. When the EN pin voltage exceeds a diode

threshold the LT3840 comes out of the low quiescent cur-

rent shutdown mode and turns on the internal reference

(VREF) and internal bias (VREG). When the EN pin voltage

exceeds its precision voltage threshold the auxiliary bias

switching regulator is activated and the INTVCC voltage

is regulated. Figure 4 is a functional block diagram of the

auxiliary bias supply start-up.

The auxiliary bias supply has its own enable pin to allow

the INTVCC to be activated independent of the controller.

INTVCC may be used to drive other circuitry in the applica-

tion such as an LDO.

Figure 3. Auxiliary Bias Supply Functional Block Diagram

Figure 4. Auxiliary Bias Supply Start-Up Functional Block Diagram

3840 F04

INTERNAL

REFERENCE

OSCILLATOR

LINEAR

REGULATOR

–

VREF

VIN

AUXVIN

INTVCC

AUXILIARY

BIAS SUPPLY

VREG

3840 F03

VIN > 18V

AUXBST

CAUXBST

LPWR

INTVCC

EXTERNAL

COMPONENTS

AUXSW1

AUXSW2

INTERNAL

COMPENSATION

AUXVIN

VREF

CINTVCC

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