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LM2904-N: LM2904-N spice model

Grégoire JANIN
Prodigy 10 points
Part Number: LM2904-N
Other Parts Discussed in Thread: LM2904, , LM2904B

Tool/software:

Hello,

I see that only LM2904 spice model is available, even in LM2904-N section, which is incorrect since a lot of features are different..

So, can you provide LM2904-N spice model or indicates how to change swing voltage at least ?

Best regards,

  • 0
    TI__Mastermind 29186 points

    Hello Gregoire,

    Are you looking to simulate the output swing from V- over output current (figure 6-11 in the datasheet)?

    I do not believe the older model contained this information.

    What difference are you looking to model?

    Best,
    Jerry

  • 0 in reply to Gerasimos Madalvanos
    Prodigy 10 points

    First, thanks for your reply.

    I do not specifically want to simulate that part of the model but I would like to simulate the same behaviour which is described into the datasheet.

    If I take the LM2904 model, the output swing is not representative of the LM2904-N part.

    example:

    Voltage output swing from rail for positive rail for LM2904(A orB) is about 1.5V

    Voltage output swing for LM2904-N is between 5 and 100mV.

    So, obviously, the spice model should be different !

    And if the LM2904-N spice model does not exist, I suggest to modify the LM2904 existing spice model to at least, have the same output swing of the LM2904-N.

    So, is it possible for TI to provide the LM2904-N spice model ?

    Or, can TI suggest me how to modify the LM2904 output swing spice model ?

    note: into the model, it is written "OUTPUT VOLTAGE SWING vs. OUTPUT CURRENT (Vo)" so I guess it can be modified.

  • 0 in reply to Grégoire JANIN
    Guru 287800 points

    The specified test conditions for these devices are different. The actual behaviour will be very similar.

    For more details, see the Application Design Guidelines.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 29186 points

    Hey Gregoire,

    The LM2904 and LM2904-N have a similar output stage construction, where a close to rail output is achieved using a constant current sink, which pulls the output low under very light loads. Below is the LM2904-N on the left, and the LM2904B on the right.

    The designs are very similar, and will have very similar behavior, with the LM2904B being able to swing closer to V- for slightly heavier loads due to an increased strength in the constant current sink driver.

    While the output voltage swings in the datasheet are specified differently, the basic function of these two devices are very similar. While on paper it may look like the LM2904-N is more capable than the LM2904B, in reality the LM2904B datasheet simply goes into more detail on the operating regions of the output stage, where the LM2904-N datasheet just leaves the operation open to interpretation.

    LM2904-N:

    LM2904B:

    Best,
    Jerry