High Voltage MOSFET is optimised for power supply start-up

10th March 2006
ES Admin
A high voltage MOSFET from Zetex Semiconductors has been introduced to handle the requirements of pre-bias supply circuitry. A 450V enhancement mode N-channel device, the ZXMN0545G4 is used in a simple linear regulator to supply PWM ICs at start-up, and is disabled once the converter is fully on.
Compared to alternative resistor dependent solutions, the MOSFET based approach is said to improve system efficiency and reduce start-up time.

To maximise resistance to high voltage creepage, the MOSFET is provided in a unique 4-pinned SOT223-package. By simply disconnecting one of the two conventional drain pin positions, the device’s new leadframe design significantly extends inter-pin spacing, which helps designers comply with UL and CE creepage distance specifications.

Characterised by low on resistance – a maximum of 50? - and supporting continuous drain currents up to 140mA, and pulsed currents of 600mA, the transistor offers a highly efficient power handling capability. Switching speed is also fast, with turn-on and rise times specified at 7ns.

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