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TPS2420 curren limit/fault

Tom Saluzzo
Expert 1280 points
Other Parts Discussed in Thread: TPS2420

TPS2420 Datasheet - http://www.ti.com/lit/ds/symlink/tps2420.pdf - page 7, Pin Description for IFLT.

IFLT:

A resistor connected from this pin to ground sets the fault current threshold (IFAULT). Currents between the fault current threshold and the current-limit are permitted to flow unimpeded for the period set by the fault timer programmed on CT. This permits loads to draw momentary surges while maintaining the protection provided by a lower average current-limit. IFLT may not be set below 1 A to maintain the Fault Current-Limit threshold accuracy listed in the RECOMMENDED OPERATING CONDITIONS table. Some parts may not current-limit or fault as expected.

Please explain this last sentence - "Some parts may not current-limit or fault as expected."

  • 0
    TI__Mastermind 42795 points
    The intent of the statement is to mean that start up could become unreliable when the current limit is set below the recommended level. For example, the CT equation becomes inacurate if the current limit is set too low. For this case, upon start up the fault timer could trip before the output had fully charged the output capacitor (due to the inadequate amount of furnished current below the 1A tolerance limit).