I'm working on an Energy Meter and I need to add 8 fully differential channels to a MSP430F5437A. I will use the ADS130E08.
My question is about the clock source for the ADS130E08. In my application Clock accuracy (in particular over the temperature) and stability are critical. At the same time I need a really cheap BOM and a small foot print. I'm thinking about using a smd cystal (32768 KHz) for the MSP430 and then sourcing the clock (from an IO PIN) to the external ADC.
Would this solution be the cheapest and with the most accurate clock source?
What should be the input clock frequency of the ADS?
I assume that you want to use the internal DCO on the F5437A device and use the 32kHz crystal clock as reference for the FLL+ module.
Is that correct?
I need 8196 SPS and considering that DRDY (Data Available) toggles at fclk/256 the input frequency should be 2.098.276 Hz which is within the limits of the ADS130E08 for an external Clock (0.7 to 2.25 MHz) . I'll need to sample 5 channels in continuous mode: (24 + (16*5)) = 104 bits.
Yes, I want to use the internal DCO on the F5437A device and use a crystal clock as reference for the FLL+ module. Again, unless there is a cheaper and smarter option. Would you recommend a high frequency crystal instead ? What are the pros and cons?
Also the F5437A should run at full speed since I need to perform a lot of calculations.
The 5437 has an universal clock module, not an FLL+. It is a superset of the FLL+ with more options.
if you can live with a small tolerance (see datasheet), you can use the internal REFO instead of than external crystal as FLL reference.
However, the FLL only produces an average frequency. The momentary DCO frequency can be higher or lower, so you'll always get a jitter.
You can run the MSP with 16MHz, put a /8 divider on SMCLK and output 2MHz SMCLK to the SMCLK ouput pin to drive your external ADC. Or, by (ab)using a timer, you can even run the MSP on 24MHz and implement a /24 divider for a 2MHz output on the timer CCR1 output.
_____________________________________Before posting bug reports or ask for help, do at least quick scan over this article. It applies to any kind of problem reporting. On any forum. And/or look here.If you cannot discuss your problem in the public, feel free to start a private conversation: click on my name and then 'start conversation'. But please do so only if you really cannot do it in a public thread, as I usually read all threads. And I prefer to answer where others can profit from it (or contribute to it) too.
Thank you very much Jens-Michael.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.