• 2019-10-07
  • Product Release

Isolated Push-Pull DC-DC Converter Delivers 1W from SOT23-6

Isolated Push-Pull DC-DC Converter Delivers 1W from SOT23-6

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 - and the firm offers a selection of transformers. To maximize reliability, the chip design has incorporated three key technologies: a soft start function, output short-circuit protection and integrated over-temperature protection. A range of SMD mounted transformers that can be tailored to your design is also available.

SCM1201A is actually an unregulated oscillator/power-driver, specifically designed for the 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, center-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 the transformer turns ratio, providing the voltage reflected back to the integrated MOSFET drains (see diagram) is below 20V (minimum drain breakdown voltage is 27V). The minimum drain pin voltage is -0.7V. The maximum operating current is 350mA (600mA abs max peak).

To minimize the degree of magnetic biasing from the push-pull topology, the drive to the two internal MOSFETs is “highly symmetrical”.

 

Typical Chip Consumption is 800μA from 5V

It comes in an SOT23-6 package and is specified for operation with its junctions between -40°C and 125°C. 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.

Over-temperature protection puts the chip into ‘sleep’ if the temperature exceeds the specified range – and subsequently self recovers once the temperature drops below a threshold within the safe operating range. The datasheet has alternative output stage suggestions – for full-wave and half-wave unipolar and bipolar outputs, and includes two transformer examples:

TTB0505-1T is 6.5 x 8.8 x 3.6mm and designed for 5Vin and 5Vout 1W operation with what looks like 1,650Vdc isolation between input and output – operating over -40°C to 125°C. There is also a 5Vin 9Vout version. TSHT5.8-01 is 12.5 x 8.7 x 5.9mm, again for 5Vin 5Vout 1W operation.

 

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