MP6002DN datasheet(8/15 Pages) MPS

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MP6002 – MONOLITHIC FLYBACK/FORWARD DC-DC CONVERTER

MP6002 Rev. 1.0

www.MonolithicPower.com

12/4/2013

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

High Voltage Startup

The MP6002 features a 100V startup circuit,

see Figure 1. When power is applied, the

capacitor at the VCC pin is charged through the

VIN pin. When the voltage at the VCC pin

crosses 6.0V without fault, the controller is

enabled. The VCC pin is then disconnected from

the VIN pin and VCC voltage is discharged via

the operating current. When VCC drops to 4.5V,

the VCC pin is reconnected to the VIN pin and

VCC will be recharged. The voltage at the VCC

pin repeats this ramp cycle between 4.5V and

6.0V. VIN needs to be higher than 10V in order

to keep high voltage startup circuit working

properly. This can be guaranteed by setting

input UVLO≥10V. It is also recommended that

the capacitor at VCC pin be no less than 1uF to

achieve stable operation. The VCC pin can be

powered with a voltage higher than 4.5V from

an auxiliary winding to reduce the power

dissipated in the internal start-up circuit. The

VCC pin is internally clamped at 8V.

Under-Voltage and Over-Voltage Detection

The MP6002 includes a line monitor circuit.

Two external resistors form a voltage divider

from the input voltage to GND; its tap connects

to the LINE pin. The controller is operational

when the voltage at the UV/OV pin is between

1.2V and 3V. When the voltage at the UV/OV

pin goes out of this operating range, the

controller is disabled and goes into standby

mode. The LINE pin can also be used as a

remote enable. Grounding the UV/OV pin will

disable the controller.

Error Amplifier

The MP6002 includes an error amplifier with its

non-inverting input connected to internal 1.2V

reference voltage. The regulated voltage is fed

back through a resistor network or an

optocoupler to the FB pin. Figure 2 shows some

common error amplifier configurations.

1.2V

COMP

VCC

PRIMARY

WINDING

1.2V

COMP

VCC

(a) Using Primary winding to provide feedback

(b) Feedback is from Secondary (Common Collector)

Figure 2—Error Amplifier Configurations

Synchronize Programmable Oscillator

The MP6002 oscillating frequency is set by an

external resistor from the RT pin to ground. The

value of RT can be calculated from:

KHz

550







The MP6002 can be synchronized to an

external clock pulse. The frequency of the clock

pulse must be higher than the internal oscillator

frequency. The clock pulse width should be

within 50ns to 150ns. The external clock can be

coupled to the RT pin with a 100pF capacitor

and a peak level greater than 3.5V.

Duty Cycle Limiting with Line Feed Forward

The MP6002 has a DMAX (maximum duty cycle)

limit at 67.5% when the LINE pin voltage is

equal to 1.3V. As VLINE increases, DMAX reduces.

Maximum duty cycle can be calculated by:

100

LINE

MAX



















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