Sudden current or voltage changes are often hazardous to electronic products. For example, transients or surges that reach microprocessor or memory components can destroy those expensive parts, and wipe out critical programming and data. Many electronic products now include surge protection circuits.

In these circuits, low value resistors sense when the current is too high so that measures can be taken upstream before the excess current causes damage. Wirewound resistors are a popular choice for these applications. They are inexpensive, available in low resistance values, have low temperature coefficients and good surge-handling capability. Riedon has served this application for years with their “LO OHM” power resistors.

Riedon’s current sense resistor options

Now, Riedon’s new SL resistors add an additional application advantage. We designed them for PC board surface mounting to satisfy the growing demand for new high density boards fabricated with automated pick-and-place equipment.

SL resistors use an alloy strip resistance element, the best design for resistance values as low as 0.005 ohms. The strip element has extremely small inductance. This feature is important where circuits involve very fast rise times; transients, or “spikes,” are common in current-sensing applications.

SL resistors are also more robust. They have only three components: the resistance strip and two leads. We weld the leads to the strip, and mold the assembly in high- temperature epoxy.

Power supplies are a major application for current sensing resistors. Space-saving surface-mount designs are especially popular in small supplies, miniature DC-to-DC converters, small battery charging circuits, switching power supplies, and uninteruptible power systems.

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