• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 415 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.

ADS1298: Figure 44 of ADS 1298 page 43

Alina Siddique
Prodigy 20 points
Part Number: ADS1298

How could two independent sources can be tied to the same point. Especially WCT_to_RLD and Eitla of RLD REF_INT of RLDREFIN, can be tied together?

  • 0
    TI__Mastermind 49956 points

    Hello Alina,

    Welcome to TI E2E forum!

    Thanks for reaching out.

    Regarding your question, figure 44 has a typo. The non-inverting input of the external amplifier must be connected to the mid-supply voltage and not to RLD_REF as mentioned in the figure.

  • 0 in reply to Praveen Aroul
    Prodigy 20 points

    Thank you Praveen, 

    The answer seems to have missed the question. 
    My question was in reference  to the internal none inverting amplifier as shown attached. Notice there are three connections. It is not so clear how could one have a voltage from wct and another that could be (avdd+avss)/2 OR RLDREF_INT Which reads, due to the bar on top, not using the RLDREF_INT.
    In either case, how could you have an ac voltage from WCT directly connected to a DC source from either the internal mid range or from the external RLD_REF pin.  You indicated that figure 44 was in error, please clarify what else is in error beside connecting the external none inverting side of the amp to the midway point between avss and avdd. Also, can the dc internal reference be used as shown in the figure or is that the error you indicated in the figure? And if so, wct is an ac voltage it might not be possible to connect it to a DC be the dc internal or external. Also, was the error mentioned in a subsequent errata  document?
    Thank you again
  • 0 in reply to Alina Siddique
    TI__Genius 11550 points

    Hi Alina,

    Figure 44 is used to show the option of using the internal RLD Amp as the buffer for the internally generated WCT signal when there is a need to drive a low-impedance load. In this configuration, the WCT signal is routed to the non-inverting input of the RLD amp through the WCT_TO_RLD switch. To disconnect the internal (AVDD+AVSS)/2 from the RLD amp, open the switch by setting RLDREF_INT = 0. The external RLD reference voltage (RLDREF pin) will not be used when the RLD amp is used as the WCT buffer. 

    Please refer to Section 9.3.1.7.3 (page 36) of the datasheet for the WCT implementation and usage. 

    Thanks.

    -TC