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LM2852: Modify average model for other output voltages

Part Number: LM2852

There is an unencrypted PSpice average model for the LM2852Y that is configured for 0.8V output voltage. The LM2852 is available in other output voltages. Is there a way to modify the model so that its simulated output voltage is 1.8V?

  • Hello Paul,
    I will forward your question to our modelling team.
    They should be able to help you.
    Regards
    Brani
  • Yes it should be possible.  Inside the unecrypted circuit looks like this when you edit it:

    .SUBCKT LM2852Y_AVG  PVIN SNS SW PGND
    R1 3 SNS 200K
    R2 3 24 40K
    C1 24 SNS 60P
    C2 3 2 10P
    C3 3 25 100P
    R3 25 2 600K
    E1 2 0 1 3 1000
    V6 1 0 DC = 0.4
    R8 0 3 200K
    *V1X 17 18
    R13 17 SW .065
    X3 PVIN PGND 17 2 0 PWM
    .ENDS LM2852Y_AVG

    R8 is the lower FB resistor internal to the sub-circuit that sets the output voltage.  I successfully changed to to output 0.9 V, 1.0 V and 1.1 V.  At 1.2 V the circuit puts out unexpected results.  I will have to consult with one of our modelling experts to see what else may be affecting it.  It may take a few days to sort out.

  • Thanks for taking a look at this John!
  • Paul,

    OK we figured this out.  The output capacitor is a subcircuit that is hard coded to have 0.8 V on the output.  Just replace it with a suitable simple capacitor and ESR resistor as shown below;

    Now you can set R8 as shown below to get 1.8 V output:

    .SUBCKT LM2852Y_AVG  PVIN SNS SW PGND
    R1 3 SNS 200K
    R2 3 24 40K
    C1 24 SNS 60P
    C2 3 2 10P
    C3 3 25 100P
    R3 25 2 600K
    E1 2 0 1 3 1000
    V6 1 0 DC = 0.4
    R8 0 3 57.14K
    *V1X 17 18
    R13 17 SW .065
    X3 PVIN PGND 17 2 0 PWM
    .ENDS LM2852Y_AVG

  • Thank you very much, John!