
RC5053
PRODUCT SPECIFICATION
14
P
Figure 9 shows the relationship between the V
OUT
voltage,
PWRGD and FAULT. To prevent PWRGD from interrupting
the CPU unnecessarily, the RC5053 has a built-in t
PWRBAD
delay to prevent noise at the SENSE pin from toggling
PWRGD. The internal time delay is designed to take about
500
μ
s for PWRGD to go low and 1ms for it to recover. Once
PWRGD goes low, the internal circuitry watches for the out-
put voltage to exceed 115% of the rated voltage. If this hap-
pens, FAULT will be triggered. Once FAULT is triggered, G1
and G2 will be forced low immediately and the RC5053 will
remain in this state until V
CC
power supply is recycled or
OUTEN is toggled.
Figure 9. PWRGD and FAULT
RATED V
OUT
V
OUT
15%
5%
–5%
t
PWRBAD
t
PWRGD
t
PWRBAD
t
FAULT
FAULT
PWRGD
Layout Considerations
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
RC5053. These items are also illustrated graphically in the
layout diagram of Figure 10. The thicker lines show the
high current paths. Note that at 10A current levels or above,
current density in the PC board itself is a serious concern.
Traces carrying high current should be as wide as possible.
For example, a PCB fabricated with 2oz copper requires a
minimum trace width of 0.15" to carry 10A.
1.
In general, layout should begin with the location of the
power devices. Be sure to orient the power circuitry so
that a clean power flow path is achieved. Conductor
widths should be maximized and lengths minimized.
After you are satisfied with the power path, the control
circuitry should be laid out. It is much easier to find
routes for the relatively small traces in the control
circuits than it is to find circuitous routes for high
current paths.
2.
The GND and SGND pins should be shorted right at the
RC5053. This helps to minimize internal ground distur-
bances in the RC5053 and prevents differences in
ground potential from disrupting internal circuit opera-
tion. This connection should then tie into the ground
plane at a single point, preferably at a fairly quiet point
Figure 10. RC5053 Layout Diagram
1
10
μ
F
10
μ
F
5.6k
0.1
μ
F
SGND
G1
OUTEN
VID0
VID1
VID2
VID3
VID4
20
19
18
17
16
15
14
13
12
11
G2
PV
CC
V
CC
SENSE
0.1
μ
F
+
+
V
OUT
L
O
PV
CC
R
C
R
IMAX
BOLD LINES INDICATE
HIGH CURRENT PATHS
C
C
C1
C
SS
C
OUT
Q1
Q2
+
C
IN
V
IN
5.6k
5.6k
56
4.7
4.7
RC5053
R
IFB
+
3
1
2
4
5
6
7
8
9
10
GND
I
MAX
I
FB
SS
COMP
VID0
VID1
VID2
VID3
VID4
PWRGD
FAULT
OT
0.1
μ
F