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!
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
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
TTFN

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RE: DIP Circuit Alternative to PCA9547D SOIC Chip
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
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
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
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
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.
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
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
Single 2-input multiplexer - 74LVC1G157
Datasheet: http://www.nxp.com/documents/data_sheet/74LVC1G157...
RE: DIP Circuit Alternative to PCA9547D SOIC Chip
RE: DIP Circuit Alternative to PCA9547D SOIC Chip
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!
Yes, that's an entirely standard notion.
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.