MP110 – 900V OFFLINE SWITCHING REGULATOR

R7

R6

R8

R5

PRO

Bus Voltage 600V

Figure 10: Input Over Voltage Protection

Setup

The input over voltage protection point can be

calculated by the following function:

INOVP

PRO

R5 R6 R7 R8

VV

R8

+

++

=

×

1206 packages should be used for resistors

R5~R8 for safety consideration and the total

value should be larger than 10M

Ω for energy

saving purpose.

The switching voltage noise could be introduced

by large R5~R8 value which disturbs the PRO

pin protection action. One ceramic cap with

around 1nF should be paralleled with PRO pin

and GND pin. It should be located near the IC to

decouple the switching voltage noise.

Frequency Jittering

MP110 provides the frequency jittering function

which simplifies the input EMI filter design and

also decreases the system cost. MP110 has the

deviation range and

effectively improve EMI by spreading the energy

dissipation over the frequency range.

Thermal

MP110

is

popular

for

high

input

voltage

application with 900V integrated MOSFET. The

thermal is the key factor to influence the output

power especially the high input voltage and high

operating

frequency.

The

turn-on

loss

is

dominant in high input voltage caused by the

parasitic cap of secondary side diode and

transformer, which bring about the IC very high

junction temperature.

In order to deliver maximum power, a proper

heatsink for MP110 should be designed for

optimum thermal performance. In addition, it’s

recommended to set the operating frequency

less than 150kHz in order to achieve better

thermal

performance

and

better

EMI

in

application.

PCB Layout Guide

PCB layout is important to achieve reliable

operation, good EMI performance, and good

thermal performance. Follow these guidelines to

optimize performance.

1) Minimize the power stage switching stage

loop area. This includes the input loop (C2–

C1-T1–U1–R12/R13–C2),

the

auxiliary

winding loop (T1–D6–C6–T1), the output loop

(T1–D8–C9–T1 and T1–D7–C7–T1) and the

RCD loop (T1–D5–R16/R17/C3–T1)

2) The input loop GND and control circuit should

be separate and only connect at C2.

3) Connecting the heatsink to the primary GND

plane improves EMI and thermal dissipation.

4) Place the control circuit capacitors (such as

those for FB, PRO and VCC pins) close to IC

to decouple switching voltage noise.

5) Enlarge the GND pad near the IC for good

thermal dissipation.

6) Keep the EMI filter far away from the

switching point.

7) The two outputs clearance distance should

satisfy the insulation requirement.

MP110 Rev. 1.01

www.MonolithicPower.com

17

6/4/2014

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