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ADS4149EVM: DAC3283EVM & ADS4149EVM loopback test

Part Number: ADS4149EVM
Other Parts Discussed in Thread: DAC3283EVM, , THS4509, DAC3283


I want to make loopback environment of DAC3283EVM & ADS4149EVM for test.

So, I will revise DAC3283EVM and ADS4149EVM.

R1 & R3 resistive network will use 25-ohm resistor not 100-ohm. Then DAC output is directly connected to ADC input through SMA cable.

ADC EVM is revised so that ADC analog input specification is met. (Vcm = 1V , differential swing = 2Vpp)

Does this circuit revision make sense?

Is R8-R9-C1 for termination around Vcm necessary? or Is it possible with AMP(THS4509) only?

I'll wait for your response.

Best regards.

Seungik Cho

  • Hi Seungik,

    If you are modifying the output of DAC3283 by changing the R1 and R2 to 25 ohms and connecting to the input of ADC4149 EVM (J6 and J8) you have two options for the input signal. These two options are discussed in section 2.2.3 Analog Input of the user guide. Here is the link for the user guide

  • Thanks,

    So, I will use THS4509 AMP output as ADC analog input.

    Because input impedance at DAC3283 output must be almost 25-ohms, I highly set resistor values of Rg(1k) and Rf(2k) up.

    I wonder that how is output voltage of THS4509 lower than input voltage of that, even though gain is (2k/1k)=2.

    THS4509 has a function of common-mode level shift and lowers output swing voltage, isn't it?

    Please give a detailed explanation to me.

  • Hi Seungik,

    For questions about THS4509 please create a new forum post with THS4509 in title so that someone from amplifier team can answer your amplifier question.