rc5037 Fairchild Semiconductor, rc5037 Datasheet - Page 9

• Manufacturer Part Number: rc5037
• Description: Adjustable Switching Regulator Controller
• Manufacturer: Fairchild Semiconductor

PRODUCT SPECIFICATION
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 RC5037. 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 47 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 (V
R
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
R
DS(ON)
DS(ON)
.
of the MOSFET and its power loss.
GS
), and therefore reduces
MOSFET Gate Bias
+12V
+5V
Figure 4. 12V Gate Bias Configuration
GNDP
VCCP
47
1 F
Q1
D1
L2
R
SENSE
C
BULK
V
OUT
RC5037
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