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Problem with TLC2264 SPICE model

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!

  • 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.
  • 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
  • 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.

  • Please see embedded picture of my circuit.

  • 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