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LTC6602 input connection

Category: Hardware
Product Number: LTC6602


I would like to use LTC6602 as filter for IQ demodulator. My modulator is MAX2021, which has differential output impedance of 53ohms. My signal has maximum frequency 640kHz and I'm would use ADC sampling rate of 2MHz - 4MHz. I would need DC block for LTC6602.

I'm planning to use circuit from this thread:  LTC6602 input and output

Instead of DC coupled single ended input, I need to modify input for AC and differential. I would use LTC6604-2.5 for output.

My question is what is optimal input circuit of LTC6602 as my source is low impedance? According to datasheet Figure 12b, it is recommended to have 1.87k resistors for bias. If I connect MAX2021 directly before 0.1uF in Figure 12b, I would get double to voltage. Would that be recommended way to use LTC6602 for low impedance AC coupled loads?

Parents Reply
  • Hello,

    I have tried different things on output. Common mode noise is getting smaller if I increase the capacitance (cutoff is lower).

    Settings has some impact to oscillation seen in output. Default setting gives much better result. I doubt that input signal frequency has any impact, since I see this common mode oscillation without any input signal.

    My question is if it is expected to see some sub harmonics of clock in output? As there is no evaluation board available, I cannot do verification.

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