• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 550 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.

TLV3494: Input range and Vss supply range

Jaehoon Lee1
Prodigy 140 points

Part Number: TLV3494

Hi,

I am using TLV3494, quad comparator.

Input ranges from -2.5V to +2.5V and I want the output to be 3.3V(High)- GND(Low).

I designed the supply voltage V+= 3.3V, V- = GND but input range is limited by the supply voltage.(V+ +0.5V to  V- - 0.5V) 

When I apply input signal from the signal generator, negative range was clamped around -1V. 

Is there any possible way to solve this problem?

Best,

Jaehoon

  • 0
    TI__Mastermind 26720 points

    Jaehoon

    Can you clarify to make sure I am understanding correctly.

    I am assuming that your input is single ended and swings from -2.5V to 2.5V and the other input probably has ground as the switching threshold.

    If that is correct, you will need to level shift the voltage so it fits in the range from -0.2V to 3.5V (abs max allows 0.5V beyond the rails without damage but the recommended range is limited to 0.2V beyond the rails).

    Please see the attached TINA schematic to show a way to shift and attenuate the signal slightly to be within the recommended range.

    Chuck

    Level Shift.TSC

  • 0 in reply to Chuck Sins
    Prodigy 140 points

    Hi Chuck,

    Thanks for your reply.

    What you understood is correct. 

    I have run the TINA simulation that you shared and it looks very well.

    Best regards.

    Jaehoon  

  • 0 in reply to Chuck Sins
    Prodigy 140 points

    Hi Chuck,

    I have a follow up question. 

    Could you please describe the internal circuit of input protection? Which component limits the input range to 0.2V beyond the rails? 

    I assume that diodes could be the one but want to make sure how this input protection circuit works.

    Best,

    Jaehoon

  • 0 in reply to Jaehoon Lee1
    TI__Mastermind 26720 points

    You are correct, the diodes are the main limitation. 

    By limiting the input voltage range, DC current through the ESD structures is limited.

    Chuck