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DIP Circuit Alternative to PCA9547D SOIC Chip

DIP Circuit Alternative to PCA9547D SOIC Chip

(OP)
Hey,

I was wondering if you guys could lend a helping hand on one of my problems or at least send me in the correct direction. I am trying to redesign a circuit and one of the components being used is a:

PCA9547D 8-channel I2C-bus multiplexer
Datasheet: PCA9547D.pdf

This chip is a SOIC and I would rather use a DIP multiplexer with the same functionality. It would allow for accessibility and easy integration.

Is this feasible? Are there alternatives? How do I go about this problem? Any help you could offer would be great! Thanks!

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

I'm not sure where you need the prodding... the chip is obviously only available in SOP, TSOP and QFN, so this chip wont do. The next step of course is to look for a similar chip available in SOIC. I'd start by searching Element14, then Digi-Key, then Mouser, then RS Components. Looks like a pretty specific purpose chip, so I wouldn't have high hopes, but definitely should be the first step.

Does that help? After you've exhausted that option, you'd need to look at exactly what the chip does in your application and look for alternatives.

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

(OP)
I do not know much about these type of circuit components. I was hoping to use a DIP style multiplexer and connect it to a PCB with a DIP socket.

This is what I know so far:

He is using 2 of the 8 channels
Has grounded A0, A1, A2 and the main ground line
He is using the first channel to collect information from a sensor and the other channel to collect information from a different sensor

Maybe you can help me answer a few questions?:

What do you mean by specific chip? What would make this chip special from other multiplexers? The circuit design is only switching between 2 different lines which is normal use from any type of multiplexer right?

Why are all the address inputs grounded?

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

"I would rather use a DIP multiplexer with the same functionality. It would allow for accessibility and easy integration."

If the above quote are the actual reasons, then what about using an SOIC-to-DIP adapter?

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

VE beat me to it... I would think a simple SOIC-to-DIP PCB could be had for a handful of dollars, if one doesn't exist for your SOIC pin-count/layout, plenty of free PCB design packages that tie directly to the boardhouse. A "custom" design would take you no more than a few hours if you've never made on before, and it sounds like it would solve your problem.

You just aren't going to find many DIP chips these days as the industry moved to surface mount components decades ago. General purpose hobby-level processors (ala MicroChip PIC, et. al.) hold the majority of DIP style left in the industry.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

(OP)
Yeah, I could do the SOIC-to-DIP PCB which is how it is currently being done. But, I am trying to reduce the breadboard design with an additional SOCI-to-DIP PCB into one total PCB for the entire design.

The DIP would allow for an easy plug and play into the circuit board.

Apparently a lot of the features are current not being used in the PCA9547D and thus I have reduced it down to a simpler circuit.

PCA9540B 2-channel I2C-bus multiplexer
PCA9540D.pdf

So I guess now my current questions are:

Are there simple DIP I²C bus multiplexers?

If not are there DIP multiplexers or other electrical components that would do the same thing as a 2-channel multiplexer?

Do all DIPS need to be programmed through a PIC?

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

Quote (mfad)

Are there simple DIP I²C bus multiplexers?
On the off chance that no one knows this off the top of their head (pretty damn likely), type the last four words into Element14, Digi-Key, Mouser and RS Components and let us know. Actually you can drop "bus" because it's redundant.

Quote (mfad)

If not are there DIP multiplexers or other electrical components that would do the same thing as a 2-channel multiplexer?
No. As you said, the A0, A1, A2 select lines are grounded, so this is not a traditional multiplexer. The selection is done via I2C, and that's the "specific" bit.

Quote (mfad)

Do all DIPS need to be programmed through a PIC?
No. What makes you think that?

BTW, I do wonder if the multiplexer is necessary at all... the bare bones I2C bus theoretically supports 127 devices. Are the two sensors really not able to sit on the same bus? It's possible, if the sensor's address really can't be changed to avoid a clash, but unless I'm missing something it seems unlikely.

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

(OP)
Thanks for all the help. This has really helped me understand what is going on with the circuit.

Alright so after additional research today I have a different path that I would like to take. Hope you can help!

Currently two HMC5883 sensors are hooked up to an Arduino I2C bus, but have fixed addresses and thus require a multiplexer.

Here is my new idea:

Both sensors have the same clock rate and was wondering could those clock lines be combined because they both share the same frequency and are being read at separate times?

If so this would simplify the multiplexer into something along the lines of using a few digital logic gates (DIP Package)to switch between the address lines of the two sensors. I can see a few problems which I am looking into... the logic gates would have to wait for a LOW or HIGH signal from the Arduino and would need to switch at a high speed. They would also need to be bi-directional logic gates (If those exist).

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

(OP)
forget the second post of the two... that circuit is incorrect... the first post is still relevant

RE: DIP Circuit Alternative to PCA9547D SOIC Chip

Quote (mfad)

Currently two HMC5883 sensors are hooked up to an Arduino I2C bus, but have fixed addresses and thus require a multiplexer.

Ah yes, fixed address. How disappointing! I concur there does not seem to be a way to put the two sensors on the one bus. Maybe Honeywell figured 3-axes ought to be enough for anybody!

Quote (mfad)

Both sensors have the same clock rate and was wondering could those clock lines be combined because they both share the same frequency and are being read at separate times?

Yes, that's an entirely standard notion.

Quote (mfad)

If so this would simplify the multiplexer into something along the lines of using a few digital logic gates (DIP Package)to switch between the address lines of the two sensors.

Assuming you meant "switch between the data lines", then yep, that'd be the idea. The cautions you mention are appropriate and can all be overcome. Given that you're only selecting between two options, a normally open and normally closed pair of solid state relays like the LH1502BAC would also suffice. An advantage of an SSR is that there is no propagation delay - the delay of the multiplexer on the data line would have to be controlled for to keep it in sync with the clock line.

An alternative would be to put one sensor on the Arduino's I2C bus and connect the other to spare digital I/O pins and create a separate software (bit-banged) I2C bus. Provided your speed requirements are not that great, there are plenty of examples of doing this with the Arduino.

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