4 Channel I2C Swith

Hi Vishal,

I am moving your post to the right forum to get you the best answer.

Regards,
Koteshwar Rao

Hello Vishal,

There are several 4 channel options: www.ti.com/.../i2c-multiplexer-switch-products.page

However, none of them support up to 125C. They all support up to 85C (even our 8 channel switches).

A 2x 1:4 generally means that you have 2 seperate 1:4 muxes (which is for I2C, since you have a SDA and SCL line seperate)

Hello Jonathan,

If 2x 1:4  means two seperate 1:4 muxes, Then the part "TCA9548APWR"  should be 2X1:8, but it is represented as 1X1:8 in Digikey. Is it correct ??

Kindly clarify!

Vishal,

It depends on how you want to think of the switch. Both nomenclatures are technically correct, depending on the thought process.

If you think of it as an I2C switch, then it is a 1x 1:8 I2C switch. Or you can think of it as a generic 2x 1:8 switch.

Most will think of it as an I2C switch, and use the 1x 1:8 nomenclature (or drop the 1x all together). In a very general sense, it is technically a 2x (2 channel) 1:8 switch, but since it is an I2C product, it becomes a single 1:8 switch because I2C requires 2 independent channels.

Hi Jonathan,

Thank you for the clarification.
We are implementing a circuit with the part "TCA9546APWR". I have Pulled up all the SCL and SDA lines to 2.5V through 1K PU resistor.
Also I have used a 10K resistor to Configure the Address lines of the mux(ie A0,A1 and A2 pins). Does this configuration works fine for us??Kindly provide your suggestion.

Regards,
Vishal.A

Vishal,

Your description of your schematic sounds great. I assume when you state that you have a 10k resistor on the address line, that it connects to the same VCC of the TCA9546A or to ground? If so, then excellent.

Just a few things to check on:
1) Are you doing any voltage translation across the switch, or is everything 2.5V (master, all slaves, etc)?
2) How many channels do you plan to have enabled at the same time? The reason I ask, is as you enable more channels, the pull up resistor currents of the connected channels will sum up, and you can quickly get a lot of current if you use a 1k pull up resistor.

For reason #2, I would actually suggest a slightly weaker pull up resistor, something more like 2.2k or 4.7k, depending on your bus speed and how many channels you plan to use at the same time.

Hi Jonathan,

1) Everything is 2.5V

2)One Channel at a time. Can we enable more than 1 channel? How can it be done?

Also we are looking for a similar Mux operating at "125C"  which is not available with TI. May I know if there is any other possibility(other than I2C switch) to MUX a signal to 4 devices(Requirement is same as the TCA9546A ).

Please let us know if there is any other way to switch a signal (1:4) and the circuit should also be able to work at 125C.

Regards,

Vishal. A

Hello Vishal,

1) Then you are fine. 2.5 V is ok.

2) You simply write to the I2C switch with a 1 bit for any channel you want enabled. For example, if you were to write 0x0F to the TCA9546A, channels 0,1,2 and 3 would all turn on/connect.


If you want an i2c-controlled i2c-switch, my product family is the only one within TI to have these switches, and we do not have any 125C compliant parts.

If you are OK with using GPIO to control the channels (then only 1 channel can be turned on at a time), we may have some other offerings, but I would need to find the right contacts. Are you OK with GPIO control?

Hi Jonathan,

We are going with  TCA9546A part itself. In the datasheet of " TCA9546A" it has mentioned that if B0=0 then channel 0 is disabled as shown below.

 

1) I would like to know what is the state of the channel(SCL/SDA pins) when it is disabled? (i.e whether is it pulled down [0] or is it in open drain[z] or active high [1] ??)

2)It is mentioned  as default state when no channel is selected(i.e when all the channels are 0). what is the state of the all the channels (SCL/SDA pins) when it is disabled? (i.e whether is it pulled down [0] or is it in open drain[z] or active high [1] ??)

Kindly clarify as soon as possible.

Regards,

Vishal. A