TXB0106: TXB0106 – Voltage Low Question

GaryC

Part Number: TXB0106
Other Parts Discussed in Thread: SN74CBTLV3245A

We use TXB0106 for the Wifi SDIO interface. The green is the input wifi data in B1. The yellow is the output wifi data in A1. Both of the VCC are used 3.3V. We just only pull high 51k resistor in B1 pin. We find the yellow waveform isn’t really low in the low level. Do you have any idea for that?

BR,

Gary

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 244030 points

The TXB has very weak output drivers (to allow other devices to override the voltage level). This looks as if something on the A1 line sources current, probably a pull-up resistor.

0 GaryC over 4 years ago in reply to Clemens Ladisch

TI__Intellectual 2625 points

Do you means, we need to pull-up a resistor on A1 line? What resistor for pull up?

BR,

Thanks.

0 Clemens Ladisch over 4 years ago in reply to GaryC

Guru 244030 points

No, I mean that you should remove the pull-up from that line (if it exists).

Please show the schematic of the circuit.

0 GaryC over 4 years ago in reply to Clemens Ladisch

TI__Intellectual 2625 points

Please refer below.

The WR24 to WR28 change to 51k ohm as datasheet recommend. Do you mean to remove WR24 to WR28?

0 Clemens Ladisch over 4 years ago in reply to GaryC

Guru 244030 points

Please show what is connected to A1.

And why are you using the TXB when both voltages are the same?

0 GaryC over 4 years ago in reply to Clemens Ladisch

TI__Intellectual 2625 points

The A1 direct connect to wifi chip without pull high resistor.

The reason for the same VCC voltage is follow their system sequence. The level shifter act a buffer to isolated input and output.

BR,

Gary

0 Clemens Ladisch over 4 years ago in reply to GaryC

Guru 244030 points

The voltage on A1 would not rise if there were not something that sources current. Are you sure that the yellow trace is A1 and not B1?

Anyway, the TXB imposes restrictions on the I/O load in order to allow level shifting and automatic direction sensing. If you do not actually need level shifting, it would be a much better idea to use an analog switch, e.g., SN74CBTLV3245A.

0 ShreyasRao over 4 years ago in reply to Clemens Ladisch

TI__Guru 56100 points

Thanks for your inputs, Clemens.

GaryC,

If you have further information on this, please do post back. I will close the thread until I hear back from you or please reply if the issue is resolved from the customer end with any information for us.

Logic

Logic forum

TXB0106: TXB0106 – Voltage Low Question