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TINA/Spice/TPS63060: Confused regarding input current

Iain Wilkie
Prodigy 160 points

Part Number: TPS63060
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

When I do a transient sim on the attached circuit, after the circuit comes up and stabilizes, I note the input current is 1.35uA (@3V input) whilst the output current into the 11K load is 325uA (@3.58V)

The input current in theory should be more than 325uA but its very low !!!

Where am I going wrong here ??

Cheers

Iain

Aker PSU.TSC

  • 0
    TI__Mastermind 39210 points

    Hi Iain,

    Since you are using a very small load resistance, all switching stops after the output voltage reaches the final expected value. The voltage on the output capacitor is enough to hold the Vout high enough and the load will discharge this slowly. Only when the output voltage drops sufficiently, will the switching start again. Since there is no switching in the device after startup in your case, you do not see any input current drawn. Try increasing the load current (to say 1A or 4 ohm load) and you will see switching after startup and an appropriate input current as well.

  • 0 in reply to Nikhil Gupta (Product Folder Models)
    Prodigy 160 points
    Hi Nikhil,

    That explains it ... thank you. However just another couple of questions ... In the transient output there is a graph called V_U2_V10 ... this is not specified anywhere in my circuit, is this and internal node of the TPS63060 macro ?
    Also is there any way top speed up the simulation, can take a fair number of seconds at the moment.

    Thank you

    Iain
  • 0 in reply to Iain Wilkie
    TI__Mastermind 39210 points

    Hi Iain,

    When simulating the device, please disable "Draw Excitation" before clicking on OK on the transient simulation pop up. This should prevent the internal node from being plotted.

    We have already tried to make it as fast as we can. You can change simulation parameters like tolerances Analysis >> Set Analysis Parameters, to make it faster, but that may come at a cost of simulation accuracy.

    The other option (if you do not care about soft start) is to provide initial conditions on the output cap, and run the simulation with the option "Use Initial Conditions". This is a little risky to setup though since you need to know the exact (or close to exact) initial conditions. Also, in this case, allow the circuit to settle down for a bit so ignore the 1st 150us or so. I have attached the file for you. Note that I used negative initial conditions. If you flip the caps around, you can change this to positive initial condition.

    Aker PSU_NG.TSC

  • 0 in reply to Nikhil Gupta (Product Folder Models)
    Prodigy 160 points
    Hi Nikhil,

    Again thanks for your swift response. This now answers all my queries 100%

    Iain