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TCA39306: TCA39306 Switch Configuration and Translation Configuration question

leo shan
Prodigy 20 points

Part Number: TCA39306

From spec  
Switch Configuration Vref1=Vref2

image.png

Translation Configuration Vcc2 >= Vref1 + 0.7 V

image.png

 

I have few questrion.

Q1:
Regardless of which configuration is used, are the HIGH levels on both sides of the MOSFET determined by the external pull-up resistors,
with only LOW levels passing through the MOSFET?
Q2:
When using the translation configuration, must EN and VREF2 be shorted together to prevent the higher-voltage side from back-feeding into the lower-voltage side,
thereby avoiding a direct conduction path from the high-voltage rail to the low-voltage rail?
since Ven = VREF1 + Vth
Q3:
Is the 200k ohm resistor required on VREF2 because there is an internal voltage difference of approximately 0.6 V?
  • 0
    TI__Guru 61061 points

    Hi Leo,

    We are still looking into this and will follow up shortly.

    Regards,

    Jack

  • 0
    Guru 326760 points

    1. Yes.

    2. This particular circuit is needed to regulate the EN voltage to Vth above Vref1. (This clamps all output voltages to Vref1, i.e., it prevents higher voltage from showing up at the low-voltage side, and it allows to generate output signals at Vref1 even without a pull-up to Vref1.)

    3. The resistor is needed to limit the current that flows into Vref2 and out of Vref1, and to have a voltage drop so that EN is lower than 3.3 V. Note that this means that the two supplies are not isolated from each other; to disable the device, you would have to pull EN low.