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tps2020

Prodigy 30 points

Replies: 4

Views: 658

Hi,

I hope I'm right here. I have question concerning the TPS2020:

Datasheet says that output voltage must not be higher than input voltage by more than 0.3V:

http://www.ti.com/lit/ds/slvs175c/slvs175c.pdf

Figure 40 of datasheet shows a typical hot-plug situation. Assume that a high capacitance of let's say 100...220µF is connected from output to ground and that the load current at the output can be very low, so low, that this capacitance is discharged very slowly.

The same scheme can be found in figure 1 of this link as well by the way:

http://www.ti.com/lit/ug/slvu226b/slvu226b.pdf
 
When the input voltage now suddenly drops, the switch is still on until the undervoltage lockout of TPS2020 turns it off at about 2...2.5V input voltage. If the input voltage furtherly drops, the output voltage can be higher than the input voltage, right?
 
Will the TPS2020 withstand this situation? Or is a diode needed connected from output to input? If so, is a Schottky sufficient? Why does the TPS2020 not have a diode already built in? Or has it one? If so, which current can it withstand?
 
 
Please have a look at the datasheet of TPS2065 too. It has a different output voltage range specification (-0.3V to 6V) in the absolute maximum ratings:
 

So I ask myself: Could there be a typo in the datasheet of TPS2020?

Thanks in advance,

Kai
  • It's referring to an enabled TPS2020 with an input source, Vin, and the output connected to a source Vin + 0.3V. This is done to protect ESD structures designed to withstand transient but not excessive DC voltage.  TPS2020 will survive the examples you gave because the part is diabled or has input voltage removed.

  • In reply to Bob Kando:

    Hi Bob,

    thanks for your fast response, I appreciate it!

    So, if a sudden and heavy short at the input can occur, leaving the TPS2020 still enabled for a brief period, would you say it is better to have an external protection diode from output to input to protect the internal ESD protection scheme? Would a Schottky diode be sufficient then?

    Kai

  • In reply to kai klaas:

    You could do that with schottky diodes but the internal structures should be good enough. We sell a lot of these usb switches and I don't see other instances where customers feel the extra protection is needed.  

  • In reply to Bob Kando:

    Thank you so much!

    Have a great weekend!

    Kai

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