High temperature, high reliability 3.5W DC-DC converter

July 09, 2013 // By Graham Prophet
High-temperature semiconductor solutions company Cissoid has introduced a reference design and evaluation kit for a versatile DC-DC converter with triple output (5V, 3.3V and 1.8V) suitable for operation from -55°C up to +225°C.

As with other Cissoid products this converter has a volcano-related name; Fuji is designed around CHT-Magma, Cissoid's high-temperature PWM controller IC. It implements a non-isolated discontinuous control mode (DCM) flyback topology with triple output. It will typically be used at a point-of-load generating locally three standard voltages from a single power supply bus that can range from +12V to +28V. The output voltage of the evaluation kit are +5V; +3.3V and +1.8V. The reference design can be modified to accommodate different voltage needs.

Default switching frequency is set to 100kHz and can be modified up to 500kHz. The flyback regulation loop is set on the +5V output. Depending on the load conditions and on the regulation requirements of the application, the design can support two additional built-in linear regulators that generate the two lowest voltages.

Fuji comes as an evaluation kit that includes a compact demonstration board, a complete application note with the electrical schematic and bill of materials. It allows immediate evaluation and integration into any custom electronic design with high temperature requirements or into an MCM hybrid project. Electrical and mechanical performance (e.g. efficiency, selection and sizing of the passive components, current output capabilities...) can be tailored to meet custom requirements; the application note brings necessary information for most of the customisation needs.

The demonstration board was designed to meet the toughest space constraints: It is 1 inch wide by 3 inches long and less than half an inch high, including all the necessary passive and active components. All the components are rated -55°C to +225°C. The transformer is a custom-made toroid model built from a standard high temperature core.

Cissoid is working with IPDiA, supplier of silicon passive components and 3D silicon packaging, to offer as an optimised solution with high-temperature silicon capacitors suitable for 250°C operation; from IPDiA, these capacitors offer improved temperature, voltage, and high reliability that far exceed the standard capacitor technology.

The EVK-Fuji