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TMCS1100: TMCS1100 Vout and Vref capacitor

Sammi Shang
Expert 4450 points
Part Number: TMCS1100

Dear team,

I see we had not add capacitor to Vout and Vref in the application design in datasheet, customer wonder if no capacitor will effect the response time and EMC test. Would you give suggestion that what value capacitor should be put beside Vout and Vref?

Thanks.

Best regards,

Sammi

  • 0
    TI__Mastermind 21805 points

    Hello Sammi,

    Thanks for reaching out on the forum. As no capacitance was specified in the datasheet electrical characteristics table for the response time specification, the absence of capacitance should not have any negative impact on the response time.  In fact that should allow for the quickest response time possible.  If your customer adds an RC filter to the output, this will slow down the response time especially as the R or C gets larger.  Also if your customer does not observe the maximum capacitance specification and they put too much capacitance on the output, the part will become unstable.  As for the VREF, as long as the voltage there is provided by a stable supply that should not be an issue. 

    As for EMC testing that involves strong electromagnetic fields directed towards the part, I would expect measurements to be disrupted.  This part utilizes hall sensors that produce a signal in response to a magnetic field.  The intended purpose is to produce a signal in response to a magnetic field generated by current running through the lead frame.  If you have some additional magnetic force directed towards this device, you can expect that it will either increase or decrease the measured output.  If your customer intends to use this device in a very noisy electromagnetic environment, I would recommend they use some sort of shielding over their device.

  • 0 in reply to Patrick Simmons
    TI__Expert 4450 points

    Hi Patrick,

    Thanks for your response.

    The reason that customer ask this question because they used other company's hall sensor before, nearly all hall sensor products require to add 4.7uF and 0.1uF capacitor between VIN and GND; add 1nF capacitor between Vout and GND, add 50pF capacitor between VREF and GND. So customer curious that why our hall sensor has no need of capacitor.

    Have you notice this difference before?

    Thanks.

    Best regards,

    Sammi

  • 0 in reply to Sammi Shang
    TI__Mastermind 21805 points

    Hello Sammi,

    For all of our current sensors including the TMCS1100, we always recommend the customer to have at least 0.1uF caps on the supply.  As for the output we usually provide a max capacitance value to not exceed to keep the part stable.  Based on a datasheet or so I saw from allegro, it looks as though they do the same.  I have not seen a datasheet yet that specified a minimum amount of capacitance on the output.  As for VREF, it makes sense to put a capacitor on that just like the supply.  A cap on Vref can minimize the impact of any noise coming from the VREF supply.