MP024-10

– PRIMARY-SIDE CC/CV REGULATOR

MP024-10 Rev.1.0

www.MonolithicPower.com

21

4/17/2017

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Maximum Switching Frequency

The maximum switching frequency should be

limited by the sampling point. The relationship

shown in the Electrical Characteristics table on

page 5. The secondary on time must be longer

Equation (15):

SM

S _ ON

PK

FBS _ Max

FB _ SD

P

O

D

NL

T

I

t

t

N

(V

V )











(15)

Combine Equation (14) and the relationship of

maximum switching frequency.

PCB Layout Guidelines

Efficient

PCB

layout

is

critical for

stable

operation,

good

EMI,

and

good

thermal

performance. For best results, refer to Figure

15 and follow the guidelines below.

1. Minimize the loop area formed by the input

capacitor, the transformer

’s primary winding,

the MOSFET drain and source of the

MP024-10, and the sensing resistor to

reduce EMI noise.

2. Minimize the voltage jumping area, such as

the MOSFET drain, the anode of the

secondary diode, etc. for better EMI.

3. Minimize the clamp circuit loop to reduce

EMI.

4. Minimize the secondary loop area of the

output diode and output filter to reduce EMI

noise.

5. Provide sufficient copper areas at the

cathode terminal of the output diode to act

as a heat sink.

6. Place the AC input away from the switching

nodes to minimize any noise coupling that

may bypass the input filter.

7. Place the bypass capacitor as close to the

IC as possible.

8. Place the feedback resistors next to FB and

minimize the feedback sampling loop to

minimize noise coupling.

9. Use

a

single-point

connection

at

the

negative terminal of the input filter capacitor

for the IC GND and bias winding return.

Top Layer

Bottom Layer

Figure 15: Recommended Layout

Design Example

Table 2 shows a design example following the

application guidelines.

Table 2: Design Example

85Vac~265Vac, 47Hz/63Hz

5V

2A

Figure 16 shows the detailed application

schematic. For more device applications, please

refer to the related evaluation board datasheets.