PINS FUNCTIONAL DESCRIPTION

DRAIN PIN:

Integrated power MOSFET drain pin. It provides

internal bias current during start-up via an

integrated high voltage current source which is

switched off during normal operation. The device

is able to handle an unclamped current during its

normal operation, assuring self protection against

voltage surges, PCB stray inductance, and

allowing a snubberless operation for low output

power.

SOURCE PIN:

Integrated power MOSFET source pin. To be

connected to an external current sense resistance

which defines the output current value.

GND

Used as the signal reference for all low level

signals. To be connected to the cold point of the

current sense resistance.

It corresponds to the low voltage supply of the

control part of the circuit. If Vdd goes below 6V,

the circuit is shut down and the start-up current

source is activated. The circuit resumes normal

internal low drop linear regulator generates the

value at 10V.

This pin receives the auxiliary unregulated

voltage from the main transformer, which can

range from 7V up to 27V during normal operation.

It delivers a start up current of 1.5mA during the

to an internal 10V low drop regulator which

Receives the voltage of the current sense

resistor, representative from the power MOSFET

drain current.

Serves as a reference for the peak power

MOSFET drain current. It is also the output of the

curent regulation function, which adjusts this

reference voltage to keep the average output

current constant. To be connected to an external

filtering capacitor.

Detects the full demagnetisation of the main

transformer, in

order

to

drive

the

current

regulation function. Refer to the application part

for further details. It is also used to prevent any

new turn on of the power MOSFET during the

demagnetisation phase.

FB PIN:

This is the inverting input of the voltage mode

error amplifier. This error amplifier is in charge of

current is lower than the nominal regulated one.

COMP PIN:

This is the output of the voltage mode error

amplifier. An external R-C network connected

between this pin and the FB pin defines the

bandwidth of the voltage regulation loop, and

insures the stability of the converter.

OSC PIN:

An RT-CT network must be connected on that pin

to define the switching frequency. Note that

varying from 7V to 10V. It provides also a

synchronisation capability, when connected to an

external frequency source.

CONNECTION DIAGRAMS (top View)

VIPer31SP

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