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TPS62122EVM questions

Anne Garafalo
Prodigy 90 points
Other Parts Discussed in Thread: TPS62122

Hi,

I have some question regarding the TPS62122EVM, the eval board for the 

TPS62122.   

1) On page 3 of the EVM datasheet it says that certain pins such as vout (J4) and ground (J3) need to be twisted and kept as short a possible.  What exactly does that mean?

2)  If I connect a wire between EN ON and JP1 that will allow the board to be turned on while  connecting the wire from EN to off will disable the circuit from being used correct? 

3)  If the circuit is forced to be off and a voltage is given to VIN does damage to the component occur.

4) Is there any way to change the output voltage of the device besides having to solder in new resistors, and if it has to do with the forward feed capacitor can you explain what its purpose is?

5) Do I need to correctly configure J7 in order for the device to work properly or do I only need a component soldered in the J7 pins if I want to measure to noise spectrum?

Thank You

  • 0
    TI__Guru**** 191445 points

    1.  J1 and J3 connection should be twisted to minimize input noise.  I often don't, but it is a good practice.  You may want to populate C2 with a bulk capacitor if your leads are long and not twisted.

    2. yes. It is a header you can use the commonly available shunts to cover the desired pins.

    3.  No so long as the input voltage is below the abs max listed in the datasheet.

    4.  You have to change the resistor divider to change the output voltage.  You may need to change the feed forward cap as well.  The FF cap adds phase boost. by introducing a zero/pole pair.  See the datasheet for details.

    5.  J7 is just an SMA connector and is not installed.  You only need to add it if you want to connect a spectrum analyzer using an SMA connection.  Otherwise you can just leave it unpopulated.

  • 0 in reply to JohnTucker
    Prodigy 90 points

    Thanks so much for the answers!  But I do not understand what the term twisted means.

  • 0 in reply to Anne Garafalo
    TI__Guru**** 191445 points

    Twisted means twisted pairs of wires.  Just like a hair braid except with 2 wires, positive and negative.

  • 0 in reply to JohnTucker
    Prodigy 90 points

    So for instance the two leads coming out of J3 should be twisted together?  Which one is connected to the input voltage or are they connected together?  Also what did you get for your output voltage, with the original resistors the eval board came with?  I'm getting 1.78 volts for vout no matter what my vin is.