DAC900: Settling Time vs. Update Rate

Jan Bock

Expert 3420 points

Part Number: DAC900

Hi Team,

My customer has the following question:

How can it be that the DAC sample rate is 165Msps while the Settling Time is 30nS ?

Does settling Time of 30nS limit the DAC sample rate to max. 33Msps (1/30nS) ?

Since the update rate of the interface is much higher than the settling, the settling time should be the limiting factor, right? Or does the update consider the output rise time. From the data sheet it is not clear how the output update rate is connected to the settling time.

It would be nice to have some more explanation.

Thanks

Jan

over 4 years ago

0 Miguel Lomeli over 4 years ago

TI__Intellectual 1950 points

Hi Jan,

Lets say you have a square wave at the dac output. At the beginning of the square wave you will have some ringing which can be overshoot/undershoot but then eventually the square wave will settle. The time it takes to settle is called the settling time. This measurement is reflected in AC performance.

0 Jan Bock over 4 years ago in reply to Miguel Lomeli

TI__Expert 3420 points

Hi Miguel,

I think in the datasheet they define the Output Settling time as rise time+ settle time. This is what it looks like to me in the timing diagram.

regards

Jan

0 Miguel Lomeli over 4 years ago in reply to Jan Bock

TI__Intellectual 1950 points

ok, still same concept

+1 Jan Bock over 4 years ago in reply to Miguel Lomeli

TI__Expert 3420 points

Hi Miguel,

the question was more directed to point out the difference between update rate an output settling time. I found another thread where it is explained for SPI interface:

e2e.ti.com/.../dac---understanding-settling-time-update-rate

thanks

Jan

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DAC900: Settling Time vs. Update Rate