• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 82 subscribers
  • Views 558 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.

TMS320F28P650DK: ADC differential mode configuration

Johnny Chen
Expert 5270 points

Part Number: TMS320F28P650DK
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi Champ,

I am asking for my customer. They are configuring ADC in 12-bit differential mode.

In differential signaling mode, it is known that the input voltage to the converter is sampled through a pair of input pins (ADCINxP and ADCINxN).

(1). A pair of input pins, it must be configured with adjacent pins as a pair of input pins (i.e. A0 and A1), not available to arbitrarily configured with any two ADC pins in the same ADC module (i.e. A0 and A3), correct ?

(2). Is there a table in datasheet / TRM which explicitly show that the pins are tied together as a pair of input pin for differential mode and the pair is available on that package ?

It is inconvenient when doing the pin assignment, since not all analog pins are available on all package / pin count, and if user (EE, not FW engineer) didn't use the Sysconfig, how do users intuitively know the selected pins for the pair of input pins do exist or not on that package ?  (at least Sysconfig will show No Device Pin Found if user has used the GUI) 

(3). In Sysconfig, after selecting SOC channel with differential, ADCINx and ADCINy, device pin name field may show No Device Pin Found if the selected analog pins are not available on that package. Why it is not showing a warning / error message to tell user not to use the pin, and ask for modifying to another pair of input pins ? 

(4). Is there a recommended app. note introducing the design of ADC Input Circuit Evaluation for differential mode ? or user could still refer to spract6a.pdf and that would be good enough.

Thanks and regards,

Johnny

  • +1
    TI__Intellectual 2270 points

    Hi Johnny,

    Please find the answers to the Queries below:

    Johnny Chen said:
    (1). A pair of input pins, it must be configured with adjacent pins as a pair of input pins (i.e. A0 and A1), not available to arbitrarily configured with any two ADC pins in the same ADC module (i.e. A0 and A3), correct ?

    That is correct.

    Johnny Chen said:
    (2). Is there a table in datasheet / TRM which explicitly show that the pins are tied together as a pair of input pin for differential mode and the pair is available on that package ?

    Below table from TRM (It tells about all the combinations for Differential channels.

    Need to refer Datasheet "Table 6-15. Analog Internal Connections" for analog pins available for each package. 

  • +1 in reply to Nilesh Khanna
    TI__Intellectual 2270 points
    Johnny Chen said:
    (3). In Sysconfig, after selecting SOC channel with differential, ADCINx and ADCINy, device pin name field may show No Device Pin Found if the selected analog pins are not available on that package. Why it is not showing a warning / error message to tell user not to use the pin, and ask for modifying to another pair of input pins ?

    In Sysconfig using the Device view options(top left corner) we need to configure the Package (By default it takes the highest Pin count Pkg).Once we select the Right Package tool will show error if those pins are not part of the chosen pkg, eg. below

    Johnny Chen said:
    (4). Is there a recommended app. note introducing the design of ADC Input Circuit Evaluation for differential mode ? or user could still refer to spract6a.pdf and that would be good enough.

    Currently there is an updated App note which users can refer. 

    Thanks,

    Nilesh