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LM48310 RF noise Issue and periodically damaging them

Tony Amos
Prodigy 50 points
Other Parts Discussed in Thread: LM48310

Hi,

I am using a LM48310 ultra low emi audio amplifier and I am having two issues. They are:

1) Radiated emi in the 2.4 ghz band

2) When output is shorted either to ground or the speaker outputs are shorted appears to damage the device. I thought it had output short circuit protection.

Is there anything I am doing wrong with the filtering on the device or configuration on the input that may be causing these issues? 

Tony

  • 0
    TI__Guru**** 189399 points

    Hi, Tony,

    Both are strange; this device is supposed to have good EMC performance, and be fully protected.

    A couple thoughts - how close is your layout to the one shown for the demo board on page 15 of the d/s?

    Pay particular attention to the power, ground, and grounding of the output filter.

    Speaking of the output filter, I would also verify the ferrite beads are optimal. I can't quite tell from your schematic what you're using. You want a relatively high impedance in the MHz range, and be carefuly --> ferrite bead current ratings are based on thermal limits, NOT minimum impedance limits (so your bead may not be acting as a bead at higher currents).

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 50 points

    Hi Don,

    You were correct on the bead not acting as a bead at the higher current limits. We changed the bead to an inductor and optimized the filter and our RF problem went away.  Thanks for your help! It steered us in the correct path to solve this problem. 

    Tony

  • 0 in reply to Tony Amos
    TI__Guru**** 189399 points

    Hi, Tony,

    Glad it worked out! Let us know if you need anything else. I'm going to close this thread.

    -d2