Electronic Design

Radiation-Hardening Power Devices

In the semiconductor industry, the use of radiation-hardened power MOS devices to avoid latchup is less common than hardening logic and memories to avoid single-event upsets.

Going the less-traveled path, IR introduced logic-level drive, rad-hard, n- and p-channel MOSFETs with vastly lower switching and conduction losses than bipolar power transistors, which have been the mainstay of satellite switching power supplies. Generally, spacecraft power-supply designers were stuck with the geriatric 2N2222A npn and 2N2907A pnp.

Compared to those bipolars, the rad-hard MOSFETS turn on somewhat faster and turn off six to nine times faster while switching five times the current. Switching losses are roughly 20 times lower, and conduction losses are cut nearly in half.

Both MOSFETs are characterized to 300 krad(Si) total ionizing dose (TID) and are single-event-effect (SEE) rated to a linear-energy-transfer (LET) level of 82 MeV(Au).

Earlier this year, IR applied its technology to a new line of radiation-hardened solid-state relays' contact bounce. Their switching times are similar to electro-mechanical relays, but there's no requirement for filters to deal with the mechanical relay's contact bounce. Buffered inputs enable them to be driven directly from logic circuits, and the parts are immune to vibration and shock. Four solid-state relay devices are involved (all normally open single-pole, single-throw): a dual device that switches 10 A at 100 V, two octal 1.5-A chips, and a single 20-A, 60-V device.

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