VIPER100A-E Ver la hoja de datos (PDF) - STMicroelectronics

Número de pieza

componentes Descripción

Fabricante

VIPER100A-E

SMPS PRIMARY I.C.

STMicroelectronics 

3 Pin Description

3 Pin Description

VIPer100A-E/ASP-E

3.1 Drain Pin (Integrated Power MOSFET Drain):

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.

3.2 Source Pin:

Power MOSFET source pin. Primary side circuit common ground connection.

3.3

VDD Pin (Power Supply):

This pin provides two functions :

● It corresponds to the low voltage supply of the control part of the circuit. If VDD goes below

8V, the start-up current source is activated and the output power MOSFET is switched off

until the VDD voltage reaches 11V. During this phase, the internal current consumption is

reduced, the VDD pin is sourcing a current of about 2mA and the COMP pin is shorted to

ground. After that, the current source is shut down, and the device tries to start up by

switching again.

● This pin is also connected to the error amplifier, in order to allow primary as well as

secondary regulation configurations. In case of primary regulation, an internal 13V

trimmed reference voltage is used to maintain VDD at 13V. For secondary regulation, a

voltage between 8.5V and 12.5V will be put on VDD pin by transformer design, in order to

stuck the output of the transconductance amplifier to the high state. The COMP pin

behaves as a constant current source, and can easily be connected to the output of an

optocoupler. Note that any overvoltage due to regulation loop failure is still detected by the

error amplifier through the VDD voltage, which cannot overpass 13V. The output voltage

will be somewhat higher than the nominal one, but still under control.

3.4 Compensation Pin

This pin provides two functions :

● It is the output of the error transconductance amplifier, and allows for the connection of a

compensation network to provide the desired transfer function of the regulation loop. Its

bandwidth can be easily adjusted to the needed value with usual components value. As

stated above, secondary regulation configurations are also implemented through the

COMP pin.

● When the COMP voltage is going below 0.5V, the shut-down of the circuit occurs, with a

zero duty cycle for the power MOSFET. This feature can be used to switch off the

converter, and is automatically activated by the regulation loop (no matter what the

configuration is) to provide a burst mode operation in case of negligible output power or

open load condition.

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