MP020-5 – OFFLINE, PRIMARY-SIDE REGULATOR WITH CC/CV CONTROL AND A 700V FET

MP020-5 Rev. 1.05

www.MonolithicPower.com

15

1/23/2014

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© 2014 MPS. All Rights Reserved.

SM

S_ ON

PK

PO

D

NL

TI

5.4 s

N(V

V )

⋅

=⋅

>

μ

⋅+

For high- or low-temperature applications,

select a maximum switching frequency below

75kHz.

PCB Layout Guide

PCB layout is very important to achieve reliable

operation, good EMI, and good thermal

performance. The following describe some

layout recommendations.

1. Minimize the loop area formed by the input

capacitor, the MP020-5 drain-source, and the

primary winding to reduce EMI noise.

2. The copper area connected to GND pins is

the heat conduction path for the MP020-5.

adequate heat-sinking.

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. In addition, sufficient copper area should

be provided at the anode and cathode terminal

of the output diode to act as a heat sink.

5. Place the AC input away from the switching

nodes to minimize the noise coupling that may

bypass the input filter.

6. Place the bypass capacitor as close as

possible to the IC and source.

7. Place the feedback resistors next to the FB

pin and minimize the feedback sampling loop to

minimize noise coupling.

8. Use a single point connection at the negative

terminal of the input filter capacitor for the

MP020-5 source pin and bias winding return.

Figure 13 shows a sample layout.

Top Layer

Bottom Layer

Figure 13: PCB Layout

Design Example

Below is a design example following the

application

guidelines

based

on

these

specifications:

Table 1: Design Example

85Vac~265Vac

5V

1A

60kHz

Figure 14 shows the detailed application

schematic This circuit was used for the typical

performance and circuit waveforms. For more

device applications, please refer to the related

evaluation board datasheets.

The transformer structure used in figure 14

could be benefit to pass the 3 wire Conducted