TXS0104E: Double translator in series

Long Le

Part Number: TXS0104E

Tool/software:

Hi TI supporter,

I'm designing my board ( red box), the I2C of U4 in my board working at 3V3 domain.
I'm adding the U3 as an translator to change from I2C_1V8 to I2C_3V3.
I wonder if it works or not. ( in controller board it have x1 TXS0104 translator and in my board have the same)
If not, can you recommend the solution replace for U3. [ Can not interference to Controller board]

Thank you so much.

6 months ago

0 Jack Guan 6 months ago

TI__Mastermind 30596 points

Hey Long,

It is possible to use the TXS-Type translators in series, but we need to ensure that the heightened VOL can be interpreted by the downstream target device (U4). Note that the I2C driver (both U1 and U4) must also be able to sink in all the current from all internal pullup resistors during it drives a logic low.

Regards,

Jack

0 Long Le 6 months ago in reply to Jack Guan

Prodigy 50 points

Thank you Jack,

I'm still not clear about the " but we need to ensure that the heightened VOL can be interpreted by the downstream target device (U4)"
All the bus have the external PU 4K7, and the U4 is MAX14724.
Please help to leave out your comments !

+1 Clemens Ladisch 6 months ago in reply to Long Le

Guru 295220 points

The TXS is a passive switch, i.e., for low I²C signals, there is a direct connection between both sides. This means that each I²C device must be able to sink the current through all pull-up resistors in parallel; and for high currents, V_OL of some devices might be higher.

The TXS has internal pull-up resistors (10 kΩ on each side, so 2.5 kΩ total), so you should remove the external pull-ups.

Logic

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TXS0104E: Double translator in series