MP2797_ADC Conversion Time

Battery Management
1

I have some questions related about ADC.

  1. In datasheet MP2797, I found information about Conversion Time:
    image
    image1018×292 20 KB

    How long does it take to convert a current or voltage parameter? Ex: i use HIGH RESOLUTION VADC SCAN and only enable scan one Cell or VTOP only but I need about 50ms to complete this conversion.
  2. i don’t want use Synchronized Voltage and Current Reading to measure VTOP and ITOP. I want to find way measure only ITOP. How can i do that?
2

Hi,
Thanks for utilizing MPS Technical Forum,

  1. The voltage and current ADCs are measured at the pack level. It is 2ms per cell. It is a bit unclear here, are you running it in a single cell application? Can you elaborate further here on your test case.
    For the MP2797 device, minimum number of cells supported is 7 series cell.

  2. VTOP and ITOP measurements are done in parallel. No other method of performing ITOP only.

Regards,
Nouman

4

I use MP2797 to monitor 15 Cell serial. I want to get more samples of ADC Current. I divide two differnce setting of HIGH RESOLUTION VADC SCAN to measure (VTOP and ITOP) and Cell Volt. With measure VTOP and ITOP, I set HIGH RESOLUTION VADC SCAN like below:
Register address:
HR_SCAN0 0x9C: 0x0202;
HR_SCAN1 0x9D: 0x0000;
HR_SCAN2 0x9E: 0x0000;
After that i start read ADC measurements (ADC_SCAN_GO trigger) and timeout to the adc scan has finished (get complete state in ADC_CTRL: 0x99 bit [1] ). I measure this process spend about 50ms (not 2ms). Have wrong setting ?

5

Thank you for your patience,

What you are possibly observing is the Internal Schedular for ADC command/execution time. . I will confirm this with internal team and get back to you based on their feedback.

6

I use ST32 F3 MCU to interface (I2C) with MP2797. Beside of MCU, i use FreeRTOS to devide two tasks. A Communicate Task is used to interface with MP2797 (polling every 5ms) and TimingTask (polling 1ms) use to timing read ADC measurements. Detail, when i trigger a start command read ADC measurements (ADC_SCAN_GO trigger) in Communicate Task, a counter variable is increase in TimingTask and the counter variable is stopped when the adc scan has finished (get complete state in ADC_CTRL: 0x99 bit [1] ). The time of this proceess = counter variable x 1ms. I try change time polling Communicate Task from 1ms to 25ms and result is more than 50ms. All setting HIGH RESOLUTION VADC SCAN above.