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LM5069: LM5069 as a swith and current limit function

Frank Xiao
Genius 12055 points
Part Number: LM5069

Hi team,

My customer want to use the device lm5069. 1. as a switch 2. do current limit function.

They use the MCU to give the signal to power ctrl to control 0v and 9v to turn on and turn off the switch.

I think it's ok to use the device like this. Could you please help double check it? Thanks( the input voltage will change 10v~60v, but change very slowly).

  • 0
    TI__Expert 5940 points

    Frank,

    It looks like it will work with some caution areas to check.

    1) Vin rising dv/dt wrt output cap needs to be such that you don't trip current limit with inrush after power up at such a low voltage.

    2) Power up at higher voltage will likely trip the fault timer if ouput C is too high.  Reason is you will be in power limit the whole time and if say 100uF is present, you need about 12ms to charge Cout with a <5ms fault timer.  Plimit may need to increase if you have large Cout and yoiu may want a longer fault time.

    3) I see your location of the Vin capacitor looks like you want to place it directly at R245, which is good.  Do not place it at Vin of the IC.  Putting it at R245 is best as it will provide DM filtering to both sides of the shunt.  This helps with CL trip and protects the current sense amp from Vos. 

    4) best to use a single 20mohm shunt.  2 in series adds inductance which is not good when fast shut off needs to happen. 

    Make sure you use the design calculator at www.ti.com/hotswap.  I think you may have already as Plimit is set about at the minimum level. 

    Brian