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TMCS1101: About TMCS1101 power supply voltage ripple requirement and saturation current

Part Number: TMCS1101

Hi CSPS team

My customer have several questions about TMCS1101 and listed below:

  1. As TMCS1101 generate the offset voltage by internal reference, this reference accuracy will have huge influence on current sensing accuracy. How we generate this reference internally? Do we have any mechanism to keep this reference stable even along with VCC voltage ripple? If this reference performance depends on power supply performance, do we have any guideline about what level of accuracy and voltage ripple spec we need for power supply?
  2. TMCS1101 datasheet demonstrate a maximum current it could measure (transient pulse current up to +/- 46A) I wondering to know what factor lead to such limitation? Is thermal consideration or magnetic saturation consideration? Customer want to figure it out its behavior during shortage or overcurrent condition.
  3. They used Allegro ACS7XX in the old design but it will be damaged during EFT test from time to time. Do we have qualification about EFT performance?

  • Hello Gabriel,

    Thanks for reaching out on the forum.

    1.  The internal reference for the device is based upon the supply voltage and an internal trimmed voltage divider.  For the bidirectional variant the supply is divided down to 0.5 x Vs, while for the unidirectional variant the supply is divided down to 0.1 x Vs.   For an idea of how this will effect the output, you can look at the PSRR specification.  For more information on calculating the error associated with PSRR, you can watch our tutorial video here.

    2.  There are a few limiting factors.  Sensitivity, reference bias, and swing to supply specifications will greatly diminish the possible measurement range for all except the A1 (50mV/A) variant. As for the A1 variant, the limiting factor is thermally related.  Boards with greater thermal sinking behavior as well as shorter load pulses will allow for higher load measurements.  For more information on board impact you may be interested in looking at this application report.

    3. Only qualifications or certifications I am aware of are: UL 1577 Component Recognition Program  and IEC/CB 62368-1.