LTC1753CSW#TRMPBF Linear Technology, LTC1753CSW#TRMPBF Datasheet - Page 20

• Manufacturer Part Number: LTC1753CSW#TRMPBF
• Manufacturer: Linear Technology

Specifications of LTC1753CSW#TRMPBF

• Lead Free Status / RoHS Status: Compliant

APPLICATIO S I FOR ATIO
LTC1753
LAYOUT CONSIDERATIONS
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1753. 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
carry 10A.
1. In general, layout should begin with the location of the
2. The GND and SGND pins should be shorted directly at
20
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.
the LTC1753. This helps to minimize internal ground
disturbances in the LTC1753 and prevents differences
in ground potential from disrupting internal circuit
operation. This connection should then tie into the
ground plane at a single point, preferably at a fairly quiet
point in the circuit such as close to the output capaci-
tors. This is not always practical, however, due to
physical constraints. Another reasonably good point to
make this connection is between the output capacitors
and the source connection of the low side FET Q2. Do
not tie this single point ground in the trace run between
the low side FET source and the input capacitor ground,
as this area of the ground plane will be very noisy.
U
U
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to
3. The small signal resistors and capacitors for frequency
4. The V
5. The (+) plate of C
6. The SENSE and V
7. OUTEN is a high impedance input and should be
8. Kelvin sense I
compensation and soft-start should be located very
close to their respective pins and the ground ends
connected to the signal ground pin through a separate
trace. Do not connect these parts to the ground plane!
close to the LTC1753 as possible. The 10 F bypass
capacitors shown at V
optimum regulation performance.
possible to the drain of the upper MOSFET. An addi-
tional 1 F ceramic capacitor between V
ground is recommended.
from the switching node. Care should be taken to isolate
SENSE and V
inductor switching signal. A 1 F is required between
the SENSE pin and the SGND pin next to the LTC1753.
If PWRGD or FAULT are in the wrong logic state for
nonobvious reasons, check the layout of the SENSE and
V
mounted as close to the SENSE pin as possible. In
addition, if feedforward compensation is in use, a
resistor in series with the feedforward capacitor might
be required. Finally, a low value resistor may be placed
between the output voltage and the SENSE pin (and the
1 F capacitor). This RC will help filter high frequency
spikes.
externally pulled up to a logic HIGH for normal
operation.
FB
traces carefully. The 1 F capacitor should be
CC
and PV
FB
MAX
from possible capacitive coupling to the
CC
and I
IN
FB
decoupling capacitors should be as
should be connected as close as
pins are very sensitive to pickup
FB
CC
at Q1’s drain and source pins.
and PV
CC
will help provide
IN
and power
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