TXS0108E: TXS0108E

ajay barge

Prodigy 30 points

Part Number: TXS0108E

Interfacing Circuit (sensor side):

Sensor output waveform:

Fig: wind direction sensor output (WIND_DIR 0-3.3)

Sensor output: ADC

Fig: wind Speed sensor output (WIND_SPEED ENT)

Sensor output: Pulse out

Problem Statement:

In our platform board we are using 8-Bit Bi-directional Level-Sifter (TXS0102DCUR) and 2-Bit Bi-directional Level-Sifter (TXS0102DCUR).

TXS0102DCUR interface circuit:

1. SENS_I2C_EN is controlled by using GPIO of controller.

2. Sensor output (WIND_SPEED ENT) is connected to B1 Terminal of

TXS0102DCUR i.e. SENS_I2C1_SDA.

3. A2 output of chip connected to controller Interrupt

PIN (MCU_I2C1_SDA).

4. Output: As expected.

TXS0108DCUR interface circuit:

Note: MAX3006EUP replaced with TXS0108DCUR.

SENS_SW_EN is controlled by using GPIO of controller.
Sensor output (WIND_SPEED ENT) is connected to B1-B8 (tested on all pins) of TXS0108DCUR.
Output of Chip A1 to A8(one pin) is connected to external interrupt Pin of controller.

Output: Not expected.

Expected Signal: TXS0108DCUR is OFF

Noise Signal: TXS0108DCUR is ON

When the TXS0108DCUR is enabled getting Noise on the signal Line. But same is not repeating in the TXS0102DCUR, as both are Bi-Directional buffer.SPI buffer issue.docx

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 317450 points

Please note that the TXS has internal 10 kΩ pull-up resistors; an unused pin like IVL8 should be pulled up, or simply left open (remove R142).

Are there any external pull-up or pull-down resistors on the lines?

0 Karan Kotadia over 5 years ago in reply to Clemens Ladisch

TI__Genius 16735 points

Hi,

I agree with what clemens has mentioned.

How long are your trace lengths? The scope shot you have provided, is that one of the inputs? Are you measuring this at the pin of the device (which pin)?

Can you zoom into your edges, it looks like a very slow signal, I want to see if there is any noise or slow edges that might be causing the internal one shot to trigger incorrectly.

Thanks!

-Karan

0 ajay barge over 5 years ago in reply to Clemens Ladisch

Prodigy 30 points

Dear Clemens Ladisch,

Thanks for the reply,

As per the TXS0108E data sheet,

A-port I/O has a pull-up resistor (RPUA) to VCCA and each B-port I/O has a pull-up resistor (RPUB) to VCCB. RPUA and RPUB have a value of 40 kΩ when the output is drivinglow. RPUAand RPUBhavea valueof 4 kΩwhenthe outputis drivinghigh.RPUAand RPUBare disabledwhenOE = Low.

1.i did not find 10K pull -up information in the respective data sheet.

2. when OE is enabled Pull-up resistor will be eabled, as per my circuit a Pull-Down of 10k is used, so Both Pull-up & Pull-Down acts as voltage divider,

Expecting small voltage on A8 pin.

How the Noise will be Eliminated, if A8 pin kept Floating,

0 Karan Kotadia over 5 years ago in reply to ajay barge

TI__Genius 16735 points

Hi,

http://www.ti.com/lit/an/scea044/scea044.pdf

Here is a guide on translating with the TXS devices, it goes into details on the internal pullups.

TheTXS0101/2/4 translators have fixed10-kΩ value pull-up resistors, the TXS0108 has variable pullups of 4kOhms and 40kOhms. This will still create a voltage divider which will cause voltages close to half Vcc, which may be causing large current draw and large noise on the other channels.

-Karan

0 ajay barge over 5 years ago in reply to Karan Kotadia

Prodigy 30 points

Dear Karan,

Thanks for the inputs,

Problem is solved, I have removed series resistor at sensor side,which was acting like voltage divider,

without any filter circuit i am feeding Sensor output to TXS0108E Pins. i am getting expected waveform at the out pins.

Logic

Logic forum

TXS0108E: TXS0108E