Isolated push-pull DC-DC converter delivers 1W from SOT23-6

August 12, 2019 //By Julien Happich
Chinese chip maker Mornsun has created a push-pull DC-DC converter chip IC with integrated MOSFETs that can deliver up to 1W through an isolation transformer.

To maximise reliability, the chip design incorporates three key technologies: a soft start function, output short-circuit protection and over temperature protection. The SCM1201A is actually an unregulated oscillator/power-driver, specifically designed for small form factor, isolated supplies. Being unregulated, output voltage depends on input voltage, transformer turns-ratio and, to a lesser extent, load current. It drives a low-profile, centre-tapped transformer primary with a supply rail between 4.5 and 8V wide DC power supply.

The secondary can be wound to provide any isolated voltage based on transformer turns ratio, providing the voltage reflected back to the integrated MOSFET drains is below 20V (minimum drain breakdown voltage is 27V). Minimum drain pin voltage is -0.7V. Maximum operating current is 350mA (600mA abs max peak). To minimise magnetic biasing from the push-pull topology, the drive to the two internal MOSFETs is “highly symmetrical”. Typical chip consumption is 800μA at 5V from an SOT23-6 package specified for operation between -40 and +125℃ at MOSFET junctions. Soft start is included to avoid potential device harm when booting up under high current conditions. Output short-circuit protection will not be impaired by any deviation in power supply parameters, not temperature, even down to -40°C.

Mornsun -

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