• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 46 subscribers
  • Views 540 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CCS/LMP90100: LMP90100 ODR

Sefa Erdogan
Prodigy 10 points
Part Number: LMP90100

Tool/software: Code Composer Studio

Hi,

To have a faster ADC read out we are planning to use 7.2MHz external clock  on LMP90100 but we've faced with some problems. First of all we set  ADC_AUXCN=0x10  (Datasheet Page 49) which chooses the external crystal  and then we measured the DRDBY pin with a oscilloscope. Results show that we have speeded up which is good but not as much as our calculations. We used the equations below in the datasheet to calculate the ODR 

ODR_Base1 = (CLKEXT) / (266,240)              ( Page 23 )
ODR_Base2 = (CLKEXT) / (16,640)

 but could not find any explanation about how to choose  266,244 or 16,640. How can i choose base1 or base2 ?  By the way oscilloscope result looks like our external clock is divided with 266,240. Like ODR_Base1.

Second question is our oscilloscope shows periodic 4 signals which are close to each other and them 30 ms break and then 4 again which has ODR_Base1 result.

Thanks in advance. 

 

  • 0
    TI__Guru* 98005 points
    Sefa,


    I'm sorry that we missed this post. It was lost in a shuffle of data converter product lines. Did you figure out the ODR_Base1/ODR_Base2 usage?

    Basically, ODR_Base1 is used for the first four data rates (1.6775 SPS to 13.42 SPS) while ODR_Base2 is used for the latter four data rates (26.83125 SPS to 214.65 SPS). The base starts at the highest data rate of each range and is divided by 1, 2, 4, and 8 to fill the rest of the options.


    Joseph Wu