Rainbow-electronics MAX8514 Manual do Utilizador descarregar pdf (Página 33)

MAX8513/MAX8514

Wide-Input, High-Frequency, Triple-Output Supplies

with Voltage Monitor and Power-On Reset

______________________________________________________________________________________ 33

Applications Information

PC Board Layout Guidelines

Careful PC board layout is critical to achieve low

switching losses and clean, stable operation. The

switching power stage requires particular attention.

Follow these guidelines for good PC board layout:

Place decoupling capacitors as close to the IC pins as

possible. Keep separate the power-ground plane (con-

nect to the sources of the low-side MOSFET, PGND,

and the output capacitor’s return). Connect the input

decoupling capacitors across the drain of the high-side

MOSFETs and the source of the low-side MOSFETs.

The signal-ground plane (connected to GND) is con-

nected to the rest of the circuit-ground return. The two

ground planes then connect together with a single con-

nection at the IC. Keep the high-current paths as short

as possible. Connect the drains of the MOSFETS to a

large copper area to help in cooling the devices, further

improving efficiency and long-term reliability.

1) Ensure all feedback connections are short and

direct. Place the feedback resistors as close to the

IC as possible.

2) Route high-speed switching nodes away from sen-

sitive analog areas (FB_, COMP, ILIM).

3) Ensure the current-sense paths for CSP and CSN

run parallel and close together to cancel any noise

pickup.

4) A reference PC board layout included in the

MAX8513 evaluation kit is also provided to further

aid layout.

b) NEGATIVE OUTPUT VOLTAGE

OUT1

OUT3N

R12

CBE

R13

R14

DRV3P

a) POSITIVE OUTPUT VOLTAGE

FB3P

OUT3P

R12

R14

R13

FB3N

DRV3N

SUP3N

L1B

MAX8513

MAX8514

Figure 7. Base-Drive Noise Reduction

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