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TAS5630 !RESET signal

Tomasz Chumiecki59048
Prodigy 10 points
Other Parts Discussed in Thread: TAS5630

Hi,

I would like to keep my TAS5630 in reset as a default state after power on. Could I simply pull-down this line with a resistor? What resistor value would you prefer for that? The input is not detailed documented in the TAS5630 data sheet.

After power on I will start the system from 3V3 µC. Is 3V3 enough to deactivate the RESET line of the TAS5630. What is the RESET input threshold? I didn't find it in data sheet...

Cheers!

Tomasz

  • 0
    TI__Mastermind 18510 points

    Tomasz, please see ELECTRICAL CHARACTERISTICS on page 11 of data sheet SLES220B for minimum high level and maximum low level logic voltages.  You can pull /RESET low with a resistor and then apply 3.3V to bring TAS5630 out of reset.  It might be a little better to pull /RESET low to shut TAS5630 down and add a pullup resistor to pull it high when /RESET is released.

    Please remember to wait until TAS5630 is fully out of reset before you start audio input signal.

    Best regards,

    Steve.

  • 0 in reply to SteveCrump
    Genius 3060 points

    Hi Steve, Thanks for your replay. The voltage level is OK then. I have overseen it. I was looking extra for !RESET signal specification and haven’t seen that !RESET is specified as one of digital inputs.

    The voltage threshold is just the part of my question. As I wrote I would like to keep the TAS5630 in reset as a default condition – every time when controller doesn’t control the amplifier board yet. Therefore I would prefer to use pull-down resistor instead of pull-up. The question is how to calculate the pull-down resistor value to be sure that !RESET signal stays surely below 0.8V, or better 0.4V. I would need to know what type of input has the !RESET line? Is it high impedance FET input? Than I could use quite high value resistor like 47k… or is it a current source input? What is the default state of the input not connected? Is the input internally pulled up or down? There is specified input leakage current for the digital inputs = 100µA. Is it also a current flowing when pulled-down? In that case, to keep the !RESET line under 0.8V I have to use resistor lower than 8k or to be sure 4k7or 3k3 – am I right?

    Thanks for your support.

  • 0 in reply to Tomasz Chumiecki
    TI__Mastermind 18510 points

    Tomasz, /RESET is a FET input, and 100uA is the maximum leakage from it, positive or negative, as specified in the section ELECTRICAL CHARACTERISTICS on page 11 of data sheet SLES220B.  You have used that figure correctly to calculate the highest pulldown resistance, around 8k.  I would suggest a value a little lower than this also to make sure that capactive coupling from around the circuit cannot excite this point.

    There is no default state for /RESET.  Its voltage must be controlled by the user as specified in the data sheet, or operation will not be predictable.

    Regards,

    Steve.

  • 0 in reply to SteveCrump
    Genius 3060 points

    Thanks Steve, I will place something like popular 4k7 to be sure the !RESET is pulled rightly down.

    My custom amplifier board is nearly fully assembled - I have to finish the mechanical design and place it on the heat sink to perform the first tests ... Could I power up the chip completely without heat sink??? just to check if the board does work?

    Cheers,

    Tomasz

  • 0 in reply to Tomasz Chumiecki
    TI__Mastermind 18510 points

    Tomasz, you can try this, but you may find that the IC enters thermal shutdown because of its quiescent power dissipation.  TAS5630 has a very good interface to a heatsink, but it depends on the heatsink for all its cooling.

    Regards,

    Steve.