What clock source to use for ADS803

karthik venkatesh

Intellectual 345 points

Other Parts Discussed in Thread: ADS803

Hi,

I am new to ADC based system design.

I am using ADS803 converter and it needs ~5MHz clock source.

I am not sure whether to use a normal 5MHz oscillator or to go for low jitter clock source.

Could you please give some suggestions ?

Regards,

Karthik

over 13 years ago

0 Tom Hendrick over 13 years ago

TI__Guru**** 179911 points

Hi Karthik,

The ADS803 is supported by our colleague's in the High Speed Data-converter group. I'll move your post over to their forum.

0 Matt Guibord over 13 years ago in reply to Tom Hendrick

TI__Genius 17340 points

Karthik,

The amount of clock jitter that a system can handle is very dependent on the input frequency. For a 1 MHz input, the external clock could have close to 50 ps of jitter before the SNR degrades. For a much higher input rate, say 100 MHz, the aperture jitter of the device (4 ps) is already going to limit your SNR to around 52 dBFS and any added jitter from the clock is going to degrade it even more.

Check out the clocking section in the datasheet for some discussion about the topic. Additionally, take a look at the following app note regarding jitter with high speed ADCs.

http://www.ti.com/lit/an/slyt075/slyt075.pdf

You can utilize the follow Excel based calculator to determine your jitter requirement based on your systems SNR needs. This is the tool I used to come up with the numbers above.

http://www.ti.com/tool/jitter-snr-calc

Regards,
Matt Guibord

Data converters

Data converters forum

What clock source to use for ADS803