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TPS43061 Tina Spice Model_Compensation Pin

Canan Simsek1
Prodigy 80 points
Other Parts Discussed in Thread: TPS43061

Hi All,

I am designing `` Input Current Regulated Boost Converter` in Current Mode with DCR sensing method. To control switching, i am using TPS43061 as external controller.

TPS43061 has Tina Spice reference model which uses FB pin of the device to regulate ouput voltage. In my application I want use external error amplifier, that is why I have cancelled the FB and SS pin of the device and connect the error amplifier output directly to the compensation pin of the TPS43061 TINA model.

But unfortunatelly comp pin is not reacting to any change and model is still try to regulate inductor current to some numbers eventhough comp pin is floating ( FB and SS pin is connected to the ground) .

I have added my circuit schematic to the post. As you will see, Average input current is sensed  with rsense, amplified and sended as input for error amplifier. Error amplifier has external reference voltage which can direct whole regulation to drive the expected inductor current. At the end system should be stable when expected inductor current is settled down.

In this simulation output voltage will be maximum 10v and will be controlled by power supply.

can you please inform me why tina model is not supporting my simulation?  Why comp pin is not reacting properly ?

Thanks and Regards

Canan Simsek

 8715.7485.TPS43061_DCRsensing.TSC

  • 0
    TI__Mastermind 41310 points

    Canan,

    The internal reference voltage of the TPS43061 is 1.22V. The FB pin is a voltage that is sampled from the output and used to set the output voltage value. The SS pin sets the Softstart time of the converter. The COMP pin is set up for compensating the loop to assure stability of the converter during operation.

    The input to the error amplifier is the FB pin, not the COMP pin. Since I have not seen this kind of control used for this product, I am not sure if your circuit is correct. I do know that you will not be able to control the output of the converter using the COMP pin.

    Britt

  • 0 in reply to Britt Brooks - Online Design Tools
    TI__Mastermind 35185 points

    Hi Britt,

    I've been working with Canan on this and the device should work in this topology. As a test I've run the attached circuit to take out some of the variables. This one grounds SS and FB to essentially turn off the internal error amplifier. I then have an external supply ramp up the COMP voltage to show that it is controlling the output.

    1616.slvm758_TPS43061_DCRsensing_forcedCOMP.TSC

    Best Regards,
    Anthony

  • 0 in reply to Britt Brooks - Online Design Tools
    Prodigy 80 points

    Hi Britt,

    Sorry if I was not clear enough. The aim of my application is regulation of the input current, so whole loop occurs in forward path. It will be a current controlled current source not current controlled voltage source. Whole system will behave like a constant current electronic load for a buck converter.  Output  is not aimed to regulate. As soon as output will be over 10V, lets say it will be restricted by a zener diode. (In real application by a power supply).

    I just didnt understand why comp pin is not reacting? I have discussed this topic with Anthony as he mentioned . Evenif comp pin is not connected circuit is somehow generating  outputs. Does this pin is already defined in the TINA Model block ? Or Tina Model block is defined just for voltage regulation?

     

    Thanks

    Canan 

     

  • 0 in reply to Canan Simsek1
    TI__Mastermind 41310 points

    Canan,

    My bad. I did not know that you had been working with Anthony.

    The COMP pin is not pre-defined.in the macro model, but the macro model has only been tested to be used with a similar topology as the reference design used.

    In Anthony's example, the device appears to be functioning, however, he is using a sense resistor between VN and VP and is only providing a single pulse to the COMP pin (at 20u, 1V, at 1m, 2.1V). The inductor current starts at about 700mA. The devices begins switching at about 200us. Vout starts at 4V and begins to rise after the switching begins.

    In your circuit, the inductor current starts at 100A, Vout starts at 10V and does not move, and switching starts at 700us. The voltage at COMP starts at 3.3V then drops to 2.1V. The output is connected to a voltage source holding it at 10V.

    Perhaps Anthony would be a better resource here. I can help with the simulator and model issues, however, I do not understand what the expected response of the circuit should be.

    Britt