Power Electronics

High Power Current Sense Resistor Qualified for Military, Aerospace Electronics

TT Electronics IRC has developed a series of high-reliability thick film chip resistors tested to MIL-PRF-55342-level specifications. Designated the LRF3W-MIL Series, the resistors are terminated on the long sides of the 1225-size chip package to provide the maximum thermal transport path, which gives the resistors their exceptionally high current-handling capability, and improves their overall reliability.

The LRF3W Series resistors meet the demanding requirements of MIL-PRF-55342. This thick film current sense resistor capable of handling up to 3 watts @70°C in a chip size that is normally limited to 1 watt. This provides a significant reduction in board footprint and overall weight, both of which are critical for space applications.

A key feature of the resistor's design is the long-side termination, which provides a shorter signal path as well as a wider termination contact with the traces on the PC board layout pads. Increasing the PC board copper land pad area to (900mm2) on each side of the chip gives the resistor the ability to handle 3 watts of power at 70°C.

The LRF3W-MIL Series resistors employ a high-reliability thick film resistive element on a high purity alumina substrate with nickel barrier layers on copper-plated wraparound terminations and a protective overcoat to ensure stability in harsh environments. Standard Sn/Pb terminations, as well as lead-free (matte Sn) terminations are available.

Resistance values for the LRF3W-MIL Series range from 0.003 to 1.0 , with tolerances available down to ±1% and TCRs to ±100ppm/°C. Operating temperature range is from -55°C to +150°C.

The resistors can be screened to MIL-PRF-55342, NASA EE-INST-002, or customer source control drawing to meet special application requirements. Typical lead time for the LRF3W-MIL Series resistors is 14 weeks if stock is not available.

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