Microchip adds GaN point-of-load converter for spacecraft

Microchip Technology has introduced a radiation-tolerant point-of-load converter using gallium nitride power devices for space processing systems. The POL-05-20S-T supplies up to 20A of output current, targeting low-voltage rails used by processors, FPGAs and other digital devices in satellites. The product is intended to address a growing requirement for local power conversion as spacecraft carry more processing capability within constrained electrical and thermal budgets.

The converter accepts input voltages from 4.75V to 13.2V and offers an adjustable output range from 0.7V to 5V, according to Microchip. This arrangement allows a spacecraft power bus to be converted locally to supply a particular digital load. The actual operating point depends on the processor supply requirement, anticipated current transients and the thermal design around the device.

Digital circuits may draw rapidly changing current as processing blocks become active or return to idle states. A local voltage regulator must manage the resulting disturbance so that the load remains within its permitted voltage limits. Excessive voltage dip can interrupt processing, while overshoot can impose electrical stress on the semiconductor load. Converter control, output capacitance and printed circuit board layout contribute to this transient behaviour.

Microchip uses a synchronous buck topology with current-mode control. In a synchronous design, controlled switching devices carry current during the relevant intervals, reducing the need to rely solely on a diode in the freewheeling path. The method can reduce conduction losses in low-voltage, high-current systems, but the advantage depends on the switching devices and their operation within the complete circuit.

Gallium nitride transistors can support rapid switching with comparatively low losses under suitable conditions. Higher switching frequencies can reduce the size of some magnetic and filtering components, although increasing frequency can also introduce losses and electromagnetic interference. Gate-drive characteristics, thermal management and parasitic inductance must therefore be assessed rather than treating GaN material selection as an efficiency guarantee.

The POL-05-20S-T is supplied in a compact surface-mount package measuring approximately 38.4mm square and 11.4mm high, with a mass of about 25g. These figures are relevant to spacecraft electronics, where a power regulator must fit close to the load while respecting board-level assembly constraints. Power density also creates heat removal requirements, especially during sustained operation at higher current.

Radiation introduces a separate qualification problem. Total ionising dose can change the electrical characteristics of semiconductor components over a mission, while individual energetic particles can produce transient effects or permanent failures. Microchip characterises the device before and after a stated 50krad total ionising dose and reports single-event testing at a specified linear energy transfer of up to 43MeV·cm²/mg. These are published component test conditions; they do not establish that every space mission or radiation environment is covered.

Thermal operation is specified across a wide temperature range, with full-load performance stated from -55°C to +100°C. System designers must consider the temperature actually reached by the mounted converter, rather than assuming ambient conditions alone describe the semiconductor junction temperature. Heat flow through the circuit board and surrounding mechanical structure influences whether the device remains within its operating limits.

Control functions include remote sensing, power-good reporting and protections relating to input and output conditions. Remote voltage sensing can account for voltage drops between the regulator and load, a useful function where small changes in rail voltage affect digital operation. Protection settings must still be coordinated with the spacecraft distribution network and the connected processor.

Microchip says the converter is available in production quantities. The release does not identify a completed flight qualification for a particular satellite or an installed customer application. Selection for a space programme will depend on the device’s test evidence, mission radiation analysis, thermal environment, derating policy and qualification of the entire power subsystem.