Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 1482 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.

Problem with TLC2264 SPICE model

Brian Kaczynski
Prodigy 210 points
Other Parts Discussed in Thread: TLC2264, TLC2274

I have the TLC2264 operating from split +/-5v supplies in a unity gain configuration and driving a 3k load.

I find that when the input exceeds about 6.5v, the output clips hard at 6.5v because the output stage cannot deliver more than about 687uA.  When I look at the datasheet, there is no such hard limit for pullup current so I'm wondering where this is coming from.

I'm using the model commented as follows:

* TLC2264 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT

* CREATED USING PARTS RELEASE 4.03 ON 07/19/93 AT 12:25

* REV (N/A) SUPPLY VOLTAGE: +/-5V

If anyone has any idea what's up with this 687uA current limit, please let me know!  I don't want to have to change my circuit to get around a stupid SPICE limitation that doesn't apply in the real circuit but on the other hand, my circuit is complicated enough that I can't design it without simulating...

Thanks in advance for any insight anyone can offer!

  • 0
    Prodigy 210 points
    Oops, sorry, I just realized my original conditions don't make much sense. It should say the output clips at +2.06v, NOT 6.5v! Sorry for the confusion.
  • 0
    TI__Prodigy 90 points
    Hi Brian,

    Could you send us a picture of the circuit you are simulating and the values of the input so we can verify this behavior?

    Thanks,
    Raymond Barakat
  • 0 in reply to Raymond Barakat1
    Prodigy 210 points

    TLC2264_test.pdf

    Hello Raymond.  I attempted to insert two files that demonstrate this behavior.  The first is a schematic of the circuit.  The circuit is actually powered from 0v and +9v and the resistor is terminated to +4.5v.  The input is a sine wave centered at +4.5v with amplitude 4v peak and the op amp is in a unity gain configuration.

    You can see that the output voltage clips at about +6.5v because the output current maxes out at around 690uA as I mentioned.

  • 0 in reply to Raymond Barakat1
    Prodigy 210 points

    Please see embedded picture of my circuit.

  • 0
    TI__Prodigy 90 points

    Hi Bryan,

    I was able to replicate your results using the TLC2264.101 model downloaded from the TLC2264 product page (687uA output current, clipping at 6.5V). When using the TLC2264.102 file, however, I was able to get about 1.1mA at the output before clipping started at around 7.8V. The TLC2264 is only specified for about 400uA in the datasheet for high voltage levels:

    If you would like to model the TLC2264 with a model with higher current drive capabilities I recommend using the TLC2264.102 file. A device which may better suit your needs is the TLC2274. I have tested it in simulation under the same conditions and have seen no signs of clipping. It was able to output the full 8.5V at 1.3mA.

    Thanks,

    Raymond Barakat