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Inquiry regarding current limit setting on TPS40170

Atsushi Okui
Genius 4015 points
Other Parts Discussed in Thread: TPS40170, CSD18537NKCS

Hello, all

Now we are considering to use TPS40170, then would like to know the current limit setting on this device.

When simulating on SwitcherPro on following condition, RILIM is calculated 8.06kohm.

Vin: 27 to 40V, Vout: 24V, Iout: 3A (this value is what we need to set as current limit)

However, when referring page3, this limit is described as 1.1A as nominal.

The attachment is the result on this simulation.

8585.TPS40170.pdf

Please let us clarify how we could understand the simulation result 1.1A as nominal.

We thank you in advance for your information.

Best regards,

  • 0
    TI__Guru**** 191445 points

    I don't know why Switcherpro reports that value for current limit nominal.  switcherpro is no longer supported , so I don't think there is any easy way to find out.  I ran a manual calculation for your current limit.  for 3 A limit, the required resistor is 8.08 k.  8.06 k is the closest standard value so it appears that is correct at least (based on ILp-p = 520mA).

  • 0 in reply to JohnTucker
    Genius 4015 points

    Hello, thank you for your prompt reply.

    We are also considering to use CSD18537NKCS with TPS40170.

    On this case, I assume that the required RILIM would be;

    RILIM = IOC*RDS(on)/IILIM = 3A*14mohm/9.0uA = 9.3kohm

    Please let me clarify whether my understanding is correct.

    Also, please let me know how did you define ILp-p = 520mA.

    We thank you once again for your information.

    Best regards,