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AFE58JD32: AFE58JD32 (EVM)load

hongyu zhang
Prodigy 60 points
Part Number: AFE58JD32
Other Parts Discussed in Thread: TX7364

Tool/software:

Hi,

I’ve been using the AFE58JD32 (EVM) recently, and I noticed that in the provided schematic, each INP pin is connected to a 49.9 Ω resistor and a 10 nF capacitor. This seems to match the test conditions specified in the datasheet: “INP with a 10-nF capacitor and is applied with source resistance RS = 50 Ω at frequency fIN = 5 MHz.” My question is, does this RS need to be adjusted based on the load?

Similarly, when using the TX7364 (EVM), I encountered the same issue. The datasheet specifies the load as being “Connected to the pulser output is 400Ω||125pF, and to the T/R switch low voltage output is 100Ω||20pF.”

If my load is 300Ω||200pF, how should the output of both chips be adjusted?

Thank you for your help!

Best regards

  • 0
    TI__Expert 7725 points

    Hi,

    Datasheet plots are taken with some specific load . TX7364 datasheet load is 400Ω||125pF and your load is 300Ω||200pF. The hd2 performance wont change across these loads . 

    For AFE58JD32 input resistance assumed is 50Ohm in datasheet and  this is used to calculate digital attenuation . Now this is going to change and you need to recalculate the digital attenuation for specific code . So only change is programming the attenuation code value. Apart from this rest everything should fine.