AD9777 overall delay

Question

Hi 
 I am using the AD9777 in an existing design of a digital feedback controller, so actual input-to-output time delay is critical. 
 What is this delay for the AD9777? (the datasheet only gives the settling time, measured from the start of the analog output). 
 Is the overall delay and "group delay" the same thing? The AD9777 datasheet lists "group delay" under terminology, but doesn't actually use the term anywhere else in the datasheet. 
 Kind regards

ADIApproved · Accepted Answer

Unfortunately this is a very old part and the 1x delay information is not available. I estimate it would be about 10-15 DAC clock cycles. Is there any reason you are not using one of our newer products like the AD9125.)

ADIApproved · Answer

In addition to the analog delay their is latency in the digital interface and interpolation. 
 The table shows latency in DAC clock periods. So it will depend on what intepolation and modulation is used. 
 The settling time is how long it takes the DAC core to settle when the digital code changes the full digital range. 
 it need to be added to the digital latency.

AD977X Latency Table

Interpolation Rate 
 Modulation Rate 
 Stage 1 Latency 
 Stage 2 Latency 
 Stage 3 Latency 
 Modulator Latency 
 Total Latency

2 
 1 
 56 
 0 
 0 
 0 
 56

2 
 2 
 56 
 0 
 0 
 20 
 76

2 
 4 
 56 
 0 
 0 
 22 
 78

2 
 8 
 56 
 0 
 0 
 21 
 77

4 
 1 
 112 
 34 
 0 
 0 
 146

4 
 2 
 112 
 34 
 0 
 20 
 166

4 
 4 
 112 
 34 
 0 
 22 
 168

4 
 8 
 112 
 34 
 0 
 21 
 167

8 
 1 
 224 
 68 
 24 
 0 
 316

8 
 2 
 224 
 68 
 24 
 20 
 336

8 
 4 
 224 
 68 
 24 
 22 
 338

8 
 8 
 224 
 68 
 24 
 21 
 337

Note: All latencies expressed in multiples of the DAC update rate, f DAC

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AD9777 overall delay