P82B715: using different vcc (12v) and sx pullup (5v) for P82B715 I2C extenders

Alvin Schmitt1

Part Number: P82B715

can I use different pullup (5v sx) and VCC and LX (12v) for P82B715 I2C extenders? What Lx pullup do I need? I was going to use 1k for sx.

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 316690 points

Section 9.1 of the datasheet says:

The P82B715 can operate with a supply voltage from 3 V to 12 V, but the logic-signal levels at Sx/Lx are independent of the supply voltage. They remain at the levels presented to the chip by the attached devices.

For the pullup resistance calculation, see section 9.2.2.2.

0 Eric Schott1 over 4 years ago in reply to Clemens Ladisch

TI__Guru 53555 points

Thanks for the help Clemens!

Hi Alvin,

Let us know if you need any help with the calculations or have any other questions about the datasheet.

Regards,
Eric Schott

0 Alvin Schmitt1 over 4 years ago in reply to Eric Schott1

Prodigy 140 points

Just got your reply - I plan to run the device at vcc=12v ; run sda,scl,I2C at 5V ; and run Lx/sx at 12 v so I guess that would work ok right? -- but I would have to provide 5 v pullups at the far end (slave) as well as at the master right?

0 Alvin Schmitt1 over 4 years ago in reply to Eric Schott1

Prodigy 140 points

0 Clemens Ladisch over 4 years ago in reply to Alvin Schmitt1

Guru 316690 points

As shown in figures 5 and 6, each bus segment needs its own pullup.

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P82B715: using different vcc (12v) and sx pullup (5v) for P82B715 I2C extenders