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TINA/Spice/TPS40090: Design for a 3 phase synchronous buck

Part Number: TPS40090
Other Parts Discussed in Thread: TINA-TI, , INA225, TPS40140

Tool/software: TINA-TI or Spice Models

Hi,

I am designing a 3 phase synchronous buck DC/DC converter with 36 V input voltage and 24 V output voltage. The maximum output power is 5kW.

I downloaded TPS40090 TINA-TI Transient Reference Design Steady State and want to simulate the 3 phase buck converter by modifying the related parameter.

Here is my question:

1. According to the datasheet of TPS40090, for three-phase mode, PWM4 is connected to 5 V (BP5). Then how to connect CS4? Should CS4 be connected to the ground?

2. Since TPS40090 is a peak current mode controller, is it necessary to add a slope compensation circuit to eliminate the second harmonic oscillation?

3. Since the output voltage is too large for TPS40090, INA225 is adopted to sense the inductor DCR current. Does it have any influence on current -sharing?

Thank you!

  • Hello,

    1. For 3phase mode, connect CS4 to CSCN pin. For 5kW output power, probably is it better to use 4phase design to reduce current each phase.

    2. TPS40090 has internal slope compensation. The slope ramp amplitude is 0.5V typcial which should be sufficienct.

    3. It should be fine to use INA225 to sense inductor current. The input differential voltage range of TPS40090 current sense amplifier it -100mV to 100mV. Keep the voltage between CSx and CSCN below 100mV with some margin when OC happens.

    One more information, the input common mode voltage of TPS40090 current sense amplifier is from 0V to 4V as listed in datasheet. It should be fine to connect CSCN to 0V, but it will be good if CSCN is connected to a positive voltage like 1V to get better current sharing at no load or light load condition.

    A TLC431 can be used to create 1.25V. Connect INA225 GND pin (pin2) and TPS40090 CSCN pin to this 1.25V.

    Thanks
    Qian
  • Thanks for your suggestions.
    About slope compensation, I still have a question. I do not see any information about the internal slope compensation in datasheet.
    Can the slope ramp amplitude (0.5) be changed?
  • Hello,

    The 0.5V slop ramp amplitude can not be changed.

    Thanks

    Qian

  • Hello,
    Since the input differential voltage range of TPS40090 current sense amplifier is -100mV to 100mV, I find that the gain of INA225 is too large. Considering the overcurrent condition, each phase current is close to 100 A. DCR of the inductor is about 0.2 mohm. So, do you have any suggestion about the current sensing?
    Thank you very much!
  • The below circuit can be used to reduce the DCR sense voltage. Refer to TPS40140 datasheet page 39 for more information.

    Or resistor divider can be used on INA225 output to reduce the voltage between CSP and CSCN.

  • Thank you for the suggestions!