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PRODUCT SPECIFICATION
RC5039
7
P
Figure 3. DAC Function Schematic
Application Guidelines
Layout Considerations
As in any high frequency switching converter, layout is very
important. Switching current from one power device to
another can generate voltage transients across the imped-
ances of the interconnecting bond wires and circuit traces.
These interconnecting impedances should be minimized by
using wide, short printed circuit traces. The critical compo-
nents should be located as close together as possible using
ground plane construction or single point grounding.
Figure 4 shows the critical power components of the con-
verter. To minimize the voltage overshoot the interconnect-
ing wires indicated by heavy lines should be part of ground
or power plane in a printed circuit board. The components
shown in Figure 4 should be located as close together as
possible. Please note that the capacitors C
IN
and C
O
each
represent numerous physical capacitors. Locate the RC5039
within 3 inches of the MOSFET, Q1. The circuit traces for
the MOSFET’s gate and source connections from the
RC5039 must be sized to handle up to 1A peak current.
Figure 4. Printed Circuit Board Power
and Ground planes or Islands
Figure 5 shows the circuit traces that require additional
lay-out consideration. Use single point and ground plane
construction for the circuits shown. Minimize any leakage
current paths on the SS PIN and locate the capacitor, C
SS
close to the SS pin because the internal current source is only
10
m
A. Provide local V
CC
decoupling between V
CC
and
GND pins. Locate the capacitor, C
BOOT
as close as practical
to the BOOT and PHASE pins.
Figure 5. Printed Circuit Board
Small Signal Layout Guidelines
+
-
BAND GAP
REFERENCE
1.26V
VID0
VID1
VID2
VID3
FB
COMP
DACOUT
ERROR
AMPLIFIER
21.5k
1.7k
10.7k
5.4k
2.7k
2.9k
DAC
+
-
L
O
CO
UGATE
PHASE
Q1
D2
V
IN
V
OUT
RETURN
RC5039
C
IN
L
+12V
RC5039
SS
GND
V
CC
BOOT
D1
L
O
CO
V
OUT
L
Q1
D2
PHASE
+V
IN
C
BOOT
C
VCC
C
SS