Local and Remote Sensing

June 7, 2005
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The sense leads of 2nd Generation Mini and Maxi modules must always be closed: either directly at the output pins (local sensing) or at the load (remote sensing).

When remote sensing is used, all of the wiring impedances – both in the sense leads and power leads – may introduce instabilities into the feedback loop. This can result in oscillation, poor transient response, activation of the output over voltage protection (OVP) or, in extreme cases, possible damage to the module. Care must always be used in lead placement and/or printed circuit board layout to minimize impedances and maximize noise immunity. If very long sense leads are used, external compensation circuitry may be required for stability.

Do not exceed 0.25 Vdc drop between -S and -Out leads. This is an important consideration if OR’ing diodes are used – they should be located in the +Output lead to avoid exceeding this rating.

When using remote sense, it is important not to exceed the maximum output power rating of the converter. The power lost in the conductors from the converter to the load must be included in the total power delivered by the converter.

Please bear in mind, if the sense pins are not closed the module will not operate in open loop and will trigger the OVP. Once the OVP has been triggered it is necessary to remove the input voltage and wait for several minutes.

Any attempt to restart the module earlier will reactivate the delay period of the OVP circuit and the module may appear defective

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