OAR1R01JP Datasheet, PDF (6/58 Pages) Token Electronics Industry Co., Ltd. – Chip Current Sense / Open-Air Current Shunts / Axial Current Sense Resistors

TOKEN Design & Select Current Sense Resistors
In order to avoid interference from stray magnetic fields, the loop area contained by the sense resistor, the
voltage sense tracks and the sense circuit input should be minimised. This means keeping the sense
circuitry as close as possible to the sense resistor and running the voltage sense tracks close to each other.
Point 5 - High Frequency Applications
Where transient or AC currents involving high frequencies are to be sensed, the self-inductance of the
resistor must be minimised. Wirewound or spiralled film parts should be avoided, in favour of bulk metal
or low value chips.
Point 6 - High Heat Dissipation
When using a metallic element shunt with high heat dissipation and low sense voltage, consideration may
need to be given to thermoelectric voltages. The junction between a metallic resistance element and metal
terminations acts as a thermocouple, generating a voltage proportional to the temperature difference across
it.
A leaded metallic element sense resistor is therefore like two thermocouples back to back. This means that,
if the temperature differences across both junctions are equal, the error voltage is cancelled out. This is
achieved by making the design thermally symmetrical, namely, by presenting both terminals with similar
heatsinking and by keeping any other heat sources thermally distant.
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Version 2010