ADP3419 datasheet(12/16 Pages) AD

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ADP3419

Rev. A | Page 12 of 16

PC BOARD LAYOUT CONSIDERATIONS

Use the following general guidelines when designing printed

circuit boards. Figure 18 gives an example of the typical land

patterns based on the guidelines given here.

•

The VCC bypass capacitor should be located as close as

possible to the VCC and GND pins. Place the ADP3419

and bypass capacitor on the same layer of the board, so

that the PCB trace between the ADP3419 VCC pin and

the MLC capacitor does not contain any via. An ideal

location for the bypass MLC capacitor is near Pin 5 and

Pin 6 of the ADP3419.

•

High frequency switching noise can be coupled into the

VCC pin of the ADP3419 via the BST diode. Therefore,

do not connect the anode of the BST diode to the VCC

pin with a short trace. Use a separate via or trace to

connect the anode of the BST diode directly to the VCC

5 V power rail.

•

It is best to have the low-side MOSFET gate close to the

DRVL pin; otherwise, use a short and very thick PCB

trace between the DRVL pin and the low-side MOSFET

gate.

•

Fast switching of the high-side MOSFET can reduce

switching loss. However, EMI problems can arise due to

the severe ringing of the switch node voltage. Depending

on the character of the low-side MOSFET, a very fast

turn-on of the high-side MOSFET may falsely turn on

the low-side MOSFET through the dv/dt coupling of its

Miller capacitance. Therefore, when fast turn-on of the

high-side MOSFET is not required by the application, a

resistor of about 1 Ω to 2 Ω can be placed between the

BST pin and the BST capacitor to limit the turn-on

speed of the high-side MOSFET.

CVCC

CBST

RBST

SHORT, THICK TRACE

TO THE GATES OF

LOW-SIDE MOSFETS

TO SWITCH

NODE

Figure 18. External Component Placement Example

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