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Original question:

LSF0102: Voltage Translator for MDIO/MDC application

LSF0102: Single Supply Translation

Vibhu Vanjari
Genius 11900 points

Part Number: LSF0102

Hello,

The video on single supply translation says, "The supply used must be at least 0.8 V larger than the lowest desired translation voltage."

Q) Is this lowest desired translation voltage referring to Vref_A?

It also says "The voltage of Vref_A must be selected as the lowest voltage to be used in the system."

Q) Vref_A can also be lower than the lowest signal voltage correct? For example if I'm translating between 3.3 and 1.8, can Vref_A also be 1.5 V?

Thanks,

Vibhu

  • 0
    TI__Genius 16735 points

    Hi Vibhu,

    For clarification when this statement is said: "The supply used must be at least 0.8 V larger than the lowest desired translation voltage."

    1. The supply at VCCB is highlighted to imply that it is referring to VCCB.

    2. Yes, Vref_A can be lower than the lowest signal voltage. For example 1.5V. However this is not recommended because lets say you are up-translating (1.8 --> 3.3), then the internal fet will turn off at 1.5V and then the RC combination of your pullup resistor and trace capacitance will slowly increase your signal to 3.3V with a RC time constant. If you are not trying to operate at a high frequency and your system will be okay with this slower rise time then you can go ahead and use a 1.5V Vref_A. 

    Thanks!

    -Karan