MP6005

– WIDE-INPUT, HIGH-EFFICIENCY FLYBACK AND FORWARD CONTROLLER

MP6005 Rev. 1.0

www.MonolithicPower.com

20

2/5/2021

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

© 2021 MPS. All Rights Reserved.

APPLICATION INFORMATION

Setting the Output Voltage

The

MP6005

has

two

feedback

modes:

primary-side regulation (PSR) and secondary-

side regulation (SSR).

In PSR mode, the converter detects the

auxiliary winding voltage from the FB pin. The

resistor dividers (RFBH and RFBL) are used for

feedback sampling (see Figure 5).

GND

FB

Na

RFBH

RFBL

Figure 6: Feedback in PSR Mode

When the primary-side power MOSFET turns

off, the auxiliary winding voltage is proportional

to the output winding. VOUT can be estimated

with Equation (3):

DOF

A

S

FBL

FBL

FBH

REF

OUT

V

-

N

N

x

R

)

R

+

(R

x

V

=

V

(3)

Where NS is the transformer’s secondary side

winding turns, NA is the transformer’s auxiliary

winding turns, VDOF is the output rectifier diode’s

forward drop, and VREF is the reference voltage

of FB.

When the main power MOSFET turns on, the

auxiliary winding voltage is negative, and VFB is

limited by an internal circuit. The FB current can

be estimated with Equation (4):

)

N

N

x

V

(

x

R

1

=

I

P

A

IN

FBH

FB

(4)

RFBH should be high enough to limit FB’s

negative current to less than 1mA. Due to FB

’s

parasitic capacitance, RFBH should be lower

than 100k

Ω.

In SSR Mode, VOUT is set by an external TL431

regulator, For example, if the regulator

’s VREF =

2.5V and VOUT = 12V, then the upper and lower

divider resistor ratio is 3:8. The regulator

generates an amplified signal and controls the

MP6005

’s COMP pin through an optocoupler

(e.g. a PC357). The COMP pin controls the

current, and the feedback signal regulates VOUT.

Setting Work Mode

After the MP6005 turns on, it outputs a 40µA

current to the MODE pin to detect the MODE

resistance. If VMODE exceeds 2.2V, the MP6005

works in PSR. Otherwise, the MP6005 works in

SSR. The MODE pin programs the dead time

between the GATE and SYNC pins. See Table

1 on page 15 for more details on MODE

programming options.

Setting Enable (EN) Control

The EN pin programs the VIN

pin’s start-up

voltage through a resistor divider. Figure 7

shows the programmable UVLO through EN.

GND

EN

RENL

RENH

VIN

GND

6.5V

Figure 7: Programmable UVLO through EN

EN’s recommended maximum voltage is 6.5V.

If the EN divider voltage exceeds 6.5V, the

resistance connected to VIN (RENH) limits the

current flowing to the EN pin. If the divider

voltage exceeds 6.5V, an internal Zener diode

on the EN pin clamps VEN. Ensure the clamped

Zener diode current is below 0.4mA.

Setting the VCC Power Supply

VCC is regulated by an internal LDO from the

VIN pin. VCC is typically regulated at 8.5V. It is

recommended to use a decoupling capacitor

between the VCC pin and GND.

In flyback mode, it is recommended to use a

minimum 1µF capacitor. VCC can also be

powered by transformer auxiliary winding to

reduce high-voltage LDO power loss.