MP8652 – 15A, 14V, HIGH FREQUENCY STEP-DOWN WITH SYNCHRONOUS GATE DRIVER

MP8652 Rev. 0.9

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12

10/26/2009

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Bottom Layer

Figure 4—PCB Layout

External Bootstrap Diode

An external bootstrap diode may enhance the

efficiency of the regulator. The applicable

conditions of external BST diode are:

Duty cycle is high: D=

IN

OUT

V

V

>65%

In these cases, an external BST diode is

recommended from the output of the voltage

regulator to BST pin, as shown in Figure.5

MP8652

SW

BST

C

L

BST

C

5V or 3.3V

OUT

External BST Diode

IN4148

+

Figure 5—Add Optional External Bootstrap

Diode to Enhance Efficiency

The recommended external BST diode is

IN4148, and the BST cap is 0.1~1µF.

Output Voltage Tracking and Sequencing

The MP8652 allows the user to program how its

output voltage ramps during startup by means

of the SS pin. Through this pin, the output

voltage can be set to either coincidentally or

rationally track another output voltage, as

shown below.

MP8652

FB

SW

SS

MP8652

FB

SW

SS

(a) Coincidentally Tracking

(a) Rationally Tracking

MP8652

FB

SW

SS

MP8652

FB

SW

SS

Figure 6—Output Voltage Tracking