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TLC5926 / 5917 etc GND trace?

Lee Mulvogue
Prodigy 150 points

With both the 5926 and 5917 (and others) each "out" pin can sink up to 120mA; so for the 5926, this add up to almost 2Amps.  Question being, where does all of this connect back to the GND net?  Is all of this current going through the single GND pin, ie. this pin's trace back to the power source GND needs to be capable of handling 2Amps?  And/or should the powerpad be connected to GND as well?

  • 0
    Mastermind 7395 points

    For both devices, the GND pin is defined to handle the current of all the outputs (although as absolute maximum ratings). I didn't see that they have a gnd pad, and anyway, for most IC devices that I know of, the gnd pad is for thermal purposes and not for electrical conduction.

  • 0
    TI__Genius 14890 points

    All current leaves the device through the ground pin.  The ABS MAX table shows the maximum ground current.  The PowerPads typically are NOT current carrying pads.  However, in most devices with the pads, the recommendation is to tie the pad to ground.  Please check with the datasheet before determining the proper pad state.

    Ground paths must be sized to handle the LED current.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 150 points

    Thanks, have now found the "Absolute Maximum Ratings Table" stating GND terminal current as a max of 1920mA for the 4926; just seemed to be a lot of current for one tiny pin to be handling all on it's own.

    Reading SLMA002 and SLMA004 seemed to indicate that the powerpad can be connected to the ground plane, but there was no indicator that the powerpad is actually electrically connected to GND, which it appears it isn't, so the pad itself won't help with the current considerations.  I had already designed the GND pin trace with quite a hefty trace width, was just checking that I had interpreted the material correctly.

  • 0 in reply to Lee Mulvogue
    TI__Genius 14890 points

    On both the TLC5926IPWP and the TLC5927IPWP the power pad is resistively tied to ground.  It is not a current path.

    Regards,

    Dick