• State TI Thinks Resolved
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 66 views
  • Users 0 members are here
Support feedback
Options
Options
Related

LMH6321: Output Swing Limitation on LMH6321/OPA227 in 5V Single-Supply 1PPS Application

Danilo A.
Mastermind 32010 points

Part Number: LMH6321
Other Parts Discussed in Thread: OPA227,

Hi Team,

Posting on behalf of our customer.

I will share this E2E post to our customer so he can reply when needed.

I am using the OPA227 and LMH6321 in a 1PPS (Pulse Per Second) buffer circuit as shown in the attached schematic. Although the design follows a single-supply configuration with a 2.5V bias (via R1325/R1326), I am unable to achieve a full 0V to 5V output swing. The output is consistently limited/clipped to a range of approximately 2.5V peak-to-peak.

 The datasheet references single-supply operation, but it appears this is only valid for small-signal swings centered at VCC/2, not for Rail-to-Rail logic-level buffering.

Even after giving the the 0V at the input of U187.3 at input the output is measured is 1.5V there is shift in the signal for 0V also.

Looking for immediate solution.

image (1).png

Regards,

Danilo

  • 0
    TI__Mastermind 19990 points

    Hi Danilo,

    The LMH6321's output swing is around ~1.5V from the rails and can further be limited when sourcing/sinking large amounts of current like the 0.255A set on CL. I would recommend the customer look at figures 5-34 and 5-35 to get a general idea of how the output swing changes versus output current. This is likely what is occurring when the customer inputs 0V and is getting 1.5V at the output as it can only swing ~1.5V from the rail, in this case (V-)+1.5V.

    Best Regards,

    Ignacio