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LSF0102/LSF0204

Guru 13485 points
Other Parts Discussed in Thread: LSF0204, LSF0102

I have some questions about LSF0102 and LSF0204:

 

1)      Voh, Vol values as function of Vref_A/B are missing

2)      I need some clarification regarding Pull-up Resistor Sizing section. Is 3mA the minimum required pass transistor current, or can I use higher value pull-ups with lower pass transistor current?

  • Hi Eli,

    1) VOH and VOL specs do not apply to the LSF family. These devices are passive switches that shut off and use pullups to translate. They do not have any current drive of their own; it is determined by the pullup resistor values.

    2) The 3 mA spec is just a guideline. The amount of current passing through the LSF depends on the amount of current sourced and sunk by the driver and receiver. In fact, the smaller the current passing through the LSF, the better performance you should see. The switch will act like a resistor when it is on, causing higher currents to induce higher voltage drops.

     

    You can read more on LSF design here: www.ti.com/lit/pdf/slva675

    What is the application for your interest in the LSF?

    -Ryan

  • Hi Ryan,

    I have a similar question from one of my customers.

    Section 11.2.5 shows a picture with GPIO mode and it does not show any pull up resistors. Are they not required in GPIO mode?
    Can we use this device to translate from portA (1.8V) to portB(3.3V) without pull up resistors in that mode?

    -Dmitry
  • Hi Dmitry, the graphic shows down-translation to 1.0 V on channels 3 and 4. The graphic implies an internal pullup to 1 V inside the GPIO device, but it could probably be stated more clearly.

    You cannot translate up using the LSF device without pullup resistors.