• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 45 subscribers
  • Views 371 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.

ADS124S06: ADS124S06 Protection diodes on 3-wire RTD typical application in d/s

Masa Katayama
Intellectual 970 points
Part Number: ADS124S06


Dear Sir,

The d/s 10.2 typical application on page 91, describes as follows;

"The additional pins are used to route the RTD excitation currents around the input filter resistors, avoiding the voltage drop otherwise caused by the filter resistors R F1 and R F4. The diodes protect the ADC inputs in the event of a miswired connection."

If a point at diode cathode side accidentally get minus voltage, ADC input (AIN1 and AIN2) can not be protected? I probably do not understand well the first sentence(it explains only AIN5 and AIN3). 

Best regards,

Masa

  

  • 0
    TI__Guru** 113765 points
    Hi Masa-san,

    The diodes are not a requirement, however you must protect the analog inputs so that the Absolute Maximum Ratings for input voltage and current are not exceeded. In the datasheet circuit for the ADS124S06 in Figure 113 the filter resistors (RF1 and RF2) should be sized appropriately for the input protection limiting current. The top diode is not necessary as there are already resistances in series with the inputs delivering the current from IDAC1. The AIN3 current path would be totally exposed without the diode if a large transient or over-voltage were applied.

    The diodes are just some additional input protection that may or may not be required depending on the system.

    Best regards,
    Bob B