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LMS33460: LMS33460

seungpyo kang
Prodigy 130 points
Part Number: LMS33460
Other Parts Discussed in Thread: TIDA-00173, , TPS3760

Hi, Now I study about your design guide name is TIDA-00173.

At TIDRB35A which layout of smps circuit, TI mention that this is overvoltae dector circuit(Picture 1)

So i wonder how below circuit can detect overvoltage.

On the circuit (Picture 2), There is HT+ pin. It is DC(+), so if we can assume that DC link volatge is 1000 V. HT(+) also 1000 V.

And divide resistor and zenor diode, finaly D32 voltage is 7.5 V.

And there is serise resistor so Vin is about 3.2 V.

In case of LMS33460, over the about 3.0 V of Vin, Vout is not 0.

But  Vin is below 3.0 V, Vout is 0.

in my understanding, because of zenor, D32 is always 7.5 V when DC link voltage is overvolate level.

             

             Q1.I wonder that How they can detect overvotalge?

             Q2. when overvoltage trip, How is Vout value

             Q3. Can i get LM33460 Pspice file?

pic. 1                                                                                          pic. 2

  • 0
    TI__Genius 14630 points

    Hi Seungpyo,

                 Q1.I wonder that How they can detect overvotalge?

    The designer of the schematic changed their perspective of the device. The LMS33460 is an undervoltage detector with an active-low output. Meaning that when VIN drops below the threshold the VOUT will go LOW to flag a fault. On the other hand you can look at it the other way also. While VIN is below the threshold and VOUT is low, that is what your consider as  your good state, and when VIN goes above the threshold and VOUT goes HIGH is your fault state. This perspective is illustrated below.

     

                 Q2. when overvoltage trip, How is Vout value

    As mentioned above Vout is going to be HIGH during an overvoltage trip.

                Q3. Can i get LM33460 Pspice file?

    Unfortunately this device is very old and we do not have the spice model.

    If you are thinking about utilizing this for your design, I would recommend using our TPS3760 instead.

    https://www.ti.com/product/TPS3760

    Jesse