FAN5037M データシートの表示（PDF） - Fairchild Semiconductor

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FAN5037M

Adjustable Switching Regulator Controller

Fairchild Semiconductor 

PRODUCT SPECIFICATION

FAN5037

Power and Ground Connections

The connection of VCCA to the 5V power supply plane

should be short and bypassed with a 0.1µF directly at the

VCCA pin of the FAN5037. The ideal connection would be a

via down to the 5V power plane. A similar arrangement

should be made for the VCCP pin that connects to +12V.

Each ground should have a separate via connection to the

ground plane below.

A 12V power supply is used to bias the VCCP. A 47Ω resis-

tor is used to limit the transient current into VCCP. A 1uF

capacitor filter is used to filter the VCCP supply and source

the transient current required to charge the MOSFET gate

capacitance. This method provides sufficiently high gate bias

voltage to the MOSFET (VGS), and therefore reduces

RDS(ON) of the MOSFET and its power loss.

Figure 4 provides about 5V of gate bias which works well

when using typical logic-level MOSFETs. Non-logic-level

MOSFETs should not be used because of their higher

RDS(ON).

MOSFET Gate Bias

+5V

+12V

47Ω

VCCP

1µF

GNDP

Q1

L2

D1

RSENSE

VOUT

CBULK

Figure 4. 12V Gate Bias Configuration

REV. 1.0.3 9/26/01

9

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