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PRODUCT SPECIFICATION
RC5037
9
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
GS
), and therefore reduces
R
DS(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
R
DS(ON)
.
MOSFET Gate Bias
Figure 4. 12V Gate Bias Configuration
V
OUT
+5V
+12V
VCCP
47
Q1
L2
R
SENSE
C
BULK
D1
1
μ
F
GNDP