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Constant output current for tlc5928

Reinaldo Imbiriba
Prodigy 20 points

Hello,

On the datasheet for the TLC5928 on page 4 in the electrical characteristics table show 37 mA max. for  constant output current. I think this is for DC current. So, if I am using output in mode pulsed (current pulsed) what is peak current by output? Can I have peak about 60mA with 50% duty cycle, then I will have 30mA mean current?

Regards,

Reinaldo

  • 0
    Mastermind 7395 points

    Hi Reinaldo,

    I don't think so. The device regulates the current to the value indicated by the reference resistor during all the "ON" time, and it has a very fast settling time in doing so. You will get a 37mA max during the ON time, for whatever cycle time you choose.

  • 0 in reply to Avi Chami1
    Prodigy 20 points

    Hi Albert,

    The question is if possible I set current for 60mA during ON time, but pulsed with duty cycle 50%. In this case by equation1 we have Riref = 840R and Icc (mean) = 30mA. 

    Thank you for your reply.

    Reinaldo

  • 0 in reply to Reinaldo Imbiriba
    Mastermind 7395 points

    I don't think that you can extrapolate the formula for current vs. resistance. The max. recommended output current is 35mA and the absolute maximum ratings are 40mA, so I don't think that you can try to output 60mA, not even for 50% of the time.

  • 0 in reply to Avi Chami1
    TI__Guru 65200 points

    Hello Albert,
    You are absolutely correct. The recommended output current is 35mA max. and therefore setting the resistor value to a lower value will operate the part out of the recommended operating condition.

    Hello Reinaldo,
    You can increase the output current by paralleling outputs. In your case getting 60mA output current can be achieved by paralleling 2 outputs. When setting the reference resistor to a value generating 30mA, you will have on the paralleled outputs 60mA.

    Best regards,
    Brigitte