MP8869GL datasheet(32/37 Pages) MPS

32 / 37 page

MP8869

– 17V, 12A, SYNCHRONOUS STEP-DOWN CONVERTER

PRELIMINARY SPECIFICATIONS SUBJECT TO CHANGE

MP8869 Rev.1.0

www.MonolithicPower.com

6/8/2016

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

External Bootstrap Diode

An external bootstrap diode can enhance the

efficiency of the regulator given the following

conditions:

 VOUT is 5V or 3.3V

 Duty cycle is high: D > 50%

In these cases, add an external BST diode from

VCC to BST (see Figure 12).

MP8869

Figure 12: Optional External Bootstrap Diode to

Enhance Efficiency

The recommended external BST diode is

IN4148, and the recommended BST capacitor

value is 0.1μF to 1μF.

PCB Layout Guidelines

(9)

Efficient

PCB

layout

critical for

stable

operation. For best results, refer to Figure 13

and follow the guidelines below. A four-layer

layout is strongly recommended to achieve

better thermal performance.

1. Place the high-current paths (PGND, VIN,

and SW) very close to the device with short,

direct, and wide traces.

2. Keep the VIN and PGND pads connected

with large copper planes.

3. Use at least two layers for the IN and PGND

trace to achieve better thermal performance.

4. Add several vias close to the IN and PGND

pads to help with thermal dissipation.

5. Place the input capacitors as close to VIN

and PGND as possible.

6. Place the decoupling capacitor as close to

VCC and PGND as possible.

7. Place the external feedback resistors next

to FB.

8. Ensure that there is no via on the FB trace.

9. Keep the switching node SW short and

away from the feedback network.

10. Keep the BST voltage path (BST, C3, and

SW) as short as possible.

NOTE:

The

recommended

layout

based

the

Typical

Application circuit on page 34.

MP8869GL Datasheet(PDF) 32 Page - Monolithic Power Systems

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