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tps2400: TPS2400 to slow an input supply

howard banks
Intellectual 580 points
Part Number: TPS2400
Other Parts Discussed in Thread: LM5069, CSD19532Q5B, CSD19536KTT, CSD19535KTT

Our equipment is powered from high capacity LiFePO4 batteries which give a 48V supply output.

I have been evaluating a DC-DC switcher circuit that has an input filter comprising 65n and 22uF on the supply.

When connected to a PSU all is well the circuit works. When i connect to a battery pack there are issues with the voltage applied to the controller. Its way in excess of the 48V supply and simulation of the circuit show it to be >100V for a short time. 

My options are to damp the filter response which has proved successful in the simulations. However, my eye was caught by the TPS2400.

If i connect the output of the filter to a N-channel FET which is controlled by the TPS2400, im hoping that i see a supply that is (1) delayed and (2) slow to rise to the 48V. Fig 9 of the datasheet.

If i develop a circuit based on Fig2 of SLVA163 will i still see the output waveform as per fig.9 of the datasheet?



Thanks

  • 0
    TI__Expert 5940 points
    Howard,

    I'm not 100% clear on your implementation (block diagram positions). Fig 2 will not work in a 48v configuration since the TPS2400 Vgate cannot go above 20v. you would be looking at a low side approach like figure 3 of SLVA163, which may or may not be desireable. Take a look at the LM5069. It provides operation to 80v with 100v peak. It provides Current limit, Softart, ov, uv, PG and will protect the FET with SOA control.

    Brian
  • 0 in reply to Brian Daugherty
    Intellectual 580 points

    Hi Brian,

    Just looking at the LM5069 datasheet. Is there an error in the typical application (8.2). It states a 48V 10A hot swap design but the design parameters in table 1 dont support this.

    Howard

  • 0 in reply to howard banks
    TI__Expert 5940 points
    Howard,

    Looks to be typo in the diagram and/or the apps section. Like 2 apps may have gotten tied into one. We will fix on a DS update as needed. Not hard to configure for 48v by adjusting ov, uv, FET selection. The CSD19532Q5B, CSD19535KTT, CSD19536KTT are all 100v FETs, what you want for a 48v system. All have excellent SOA, again what you need. Remember that in fault conditions, Vin can overshoot and a TVS is needed. Likewise an output Schottky is needed to prevent Vout from going well below ground. Go to www.ti.com/hotswap and you can download the LM5069 design calculator tool that makes this easy to design without hand crunching. Also good app notes and tutorial videos you can pull down.

    Brian