LM3401MMX National Semiconductor Corporation, LM3401MMX Datasheet - Page 12

• Manufacturer Part Number: LM3401MMX
• Description: Hysteretic Pfet Controller For High Power Led Drive
• Manufacturer: National Semiconductor Corporation

The SNS and HYS resistors should be placed close to their
respective pins and grounded close to the GND pin. An iso-
lated ground area shown as SGND in Figure 10 is recom-
mended for the SNS, HYS, and GND pin connections. The
two ground areas, GND and SGND, should be connected on
an inner or bottom layer. This connection is shown as two vias
in Figure 10.
A large, continuous ground plane can also be used, as long
as the input capacitor and catch diode ground area is some-
what isolated.
The HG trace should be kept as short as possible to minimize
inductance and gate ringing (See HG and PFET selection
30021440
section).
Finally, for accurate current limit sensing, the CS pin and ILIM
FIGURE 10. Example PCB Layout
resistor connections should be made at the PFET pads, via
separate traces.
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