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ADC3441: output data rate on LVDS

GR
Expert 2761 points
Part Number: ADC3441
Other Parts Discussed in Thread: ADC3442

Hi

May I have question about ADC344x?

My customer is considering ADC3441 for RX in mmWave rader sensor.

Question 1 :

I think ADC344x have max sampling rate in each device.

Could we use another sampling rate less than to this value? Or could use only this sampling rate?

--

Question 2:

ADC344x Digital Output Interface's interface option means per channel?

if one wire mode selected, we could transmit 4 ch data in same timing  if using 4 lane LVDS?

--

Question 3 : 

I want to connect ADC344x to AM273x.

AM273x side,  LVDS data rate is determined.

So we should change sampling rate from default value.

I want to check could we use as this case:

case 1:

ADC3442, 2 wire(default), data rate:150 Mbps, DDR clock:75MHz

case 2:

ADC3441, 1 wire, data rate:225Mbps, DDR clock:112.5MHz

Thanks,

GR

  • +1
    TI__Mastermind 21235 points

    Hi GR,

    1. Yes, these are the max sampling rate for each device. Each device can sample slower than the max.

    2. Yes, one wire vs two wire refers to each output lane. The device can have 4 pairs of outputs (with serialization rate of 7) vs 8 pairs of output (with serialization rate of 14). Both modes use double data rate (DDR) style DCLK.

    3. Instead of thinking from data rate perspective, first choose a sample rate to achieve the needed nyquist boundary. Then simply calculate the output data rate by multiplying the sample rate with the appropriate serialization factor (dependent upon 1-wire or 2-wire output modes). Note that the frame clock behavior is different between these two modes as well. 

    The first case of 150Mbps in 2-wire mode means serialization of 7x, and sample rate would be 150M/7=21.42857 … MSPS. Since the ADC3442 is a 50MSPS device, this is valid.

    The second case of 225Mbps in 1-wire mode (14x serialization) means sample rate would be 225M/14=16.071428… MSPS. ADC3441 is a 25MSPS choice and this is also valid.

    In both of the cases above, the sample rate is not a nice, rounded number. It doesn’t have to be, but most customers prefer a sample rate for their system calculations and frequency planning that is easy to work with and remember.

    Thanks, Chase

  • 0 in reply to Chase W
    Expert 2761 points

    Hi Chase,

    Thanks for your information.

    I understand it.

    Best regards,

    GR