TCA9546A: Confirming 18.V to 3.3V operation

Ramgopal Divakar

Part Number: TCA9546A

Hello,

we have used TCA9546APWR successfully over several designs. All the rails were 3.3V then. For this design few slaves are at 1.8V.

My host is at 3.3V, SC2/SD2 shall be connected to slave devices at 1.8V rail. Remaining SC/SD pins will be connected to slaves at 3.3V.

Based on figure 16 of the datasheet, it appears I must power TCA9546APWR with 1.8V this time instead of 3.3V.

Thanks,

Divakar

4 months ago

0 Ramgopal Divakar 4 months ago

Expert 1335 points

0 Ramgopal Divakar 4 months ago in reply to Ramgopal Divakar

Expert 1335 points

Host is pulled up to 3.3V at the source close to the processor.

0 Katy West 4 months ago in reply to Ramgopal Divakar

TI__Genius 11805 points

Hi Divakar,

When the pull-up voltages are different, Vpass must be no larger than the lowest bus voltage. In your case, that would mean Vpass <= 1.8V. Based on the application curve, with a Vpass <=1.8V, VCC must be less than ~2.8V, so 1.8V would be a good supply voltage.

Best,
Katy

0 Ramgopal Divakar 4 months ago in reply to Katy West

Expert 1335 points

Thanks, the schematic illustration is good? See above

0 Katy West 4 months ago in reply to Ramgopal Divakar

TI__Genius 11805 points

Hi Divakar,

You would just need to make sure VCC is not connected to 3.3V, at it still appears to be connected.

Best,
Katy

0 Ramgopal Divakar 4 months ago in reply to Katy West

Expert 1335 points

It isn't. It just has the name that way. Power flows right to left. I will change the name.

0 Katy West 4 months ago in reply to Ramgopal Divakar

TI__Genius 11805 points

Ok, then no concern

Katy

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TCA9546A: Confirming 18.V to 3.3V operation