• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 318 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

OPA388-Q1: About Protection

alikaan
Expert 2200 points
Part Number: OPA388-Q1
Other Parts Discussed in Thread: OPA388, OPA2388

Hi,

I would like to add overvoltage protection to the input side of OPA388. Do you have any suggestion ? 

  • 0
    Guru 281530 points

    What voltage? And what should happen during such an event? (The 10 kΩ resistors already limit the current through the internal clamping diodes for up to 100 V.)

  • 0 in reply to Clemens Ladisch
    Expert 2200 points

    We are measuring high current nearly 70Amperes. Current might increase too much. When current flow increase, I would like to protect the measurement line.

  • 0 in reply to alikaan
    TI__Guru 54426 points

    HI Aikaan,

    Can you please clarify what is the maximum voltage that will be seen in nodes IA_R_SENSE_N and IA_R_SENSE_P with respect to the OPA388 GND during a fault condition?  What is the value of the shunt resistor?  

    Luis 

  • 0 in reply to Luis Chioye
    Expert 2200 points

    Maximum voltage is nearly 5VDC but it might exceed this value. That's why I would like to add overvoltage protection.

  • 0 in reply to alikaan
    TI__Guru 54426 points

    Hi Alikaan,

    The OPA2388 can withstand up to ±10mA at the inverting and non-inverting terminals during a temporary fault condition.

    Since the device is configured in a difference amplifier configuration with input series resistors R43, R49 of 10kΩ, in the event of exposure to ~ ±100V during a fault, the current through the inputs of the op-amp will be limited to ±100V/10kΩ = 10mA.  Hence, the difference amplifier configuration can withstand up to 100V at the n nodes IA_R_SENSE_N and IA_R_SENSE_P with respect to the OPA388 GND.

    In your application, if you foresee that the device will be exposed to an even larger voltage exceeding ~100V at the n nodes IA_R_SENSE_N and IA_R_SENSE_P inputs of the difference amplifier, then in this case, you will need to add external clamps, using Schottky diodes. 

    Nevertheless, to design the clamp the user needs to define the maximum over-voltage condition to properly design the external clamp.

    Please review the TI Precision Lab Session explaining overstress or EOS protection:

    https://www.ti.com/video/series/precision-labs/ti-precision-labs-op-amps.html

    To find the session on EOS protection, look into "Topics" and browse the bottom of the page, you will find 4-sessions on op-amp:

     

    Here is also a short article that discusses the op-amp input protection using Schottky diodes protecting an op-amp.

    https://www.ednasia.com/provide-robust-input-overvoltage-protection-for-amplifier-analog-input-modules/

    Let us know if you have any questions,

    Best Regards,

    Luis