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LM4550B: SDATA_OUT current consumption

Part Number: LM4550B

We have three LM4550B codecs with the SDATA_OUT lines chained together and driven from an FPGA pin.

When the FPGA pin drive strength is set to 2mA, we get a very rounded square wave and on about 1% of boards the codecs will occasionally fail to initialize correctly. If we increase the drive strength to 4mA the problem goes away.

Is there data on the current consumption of the SDATA_OUT input? We'd like to get some hard numbers on why the problem is occurring.

Regards,

Glenn

  • Hello Glenn,

    The inputs should have a fairly high DC impedance and the current draw you're seeing is likely due to the charging/discharging of the SDIN input capacitance combined with any extra cabling/PCB capacitance on that line.  If you have any snubbers or other networks on these lines they will also affect the current requirements.