What serial interface does this chip uses exactly? MAX11205

[userx2]

Hello,

I am looking at using this Maxim ADC chip but I have not been able to figure out what interface it actually uses.
https://www.analog.com/en/products/max11205.html

MAX11205 Datasheet


Their DS is rather vague and they just claim it is compatible with "with the 2-wire interface" but not much further detail.
I wonder if it is some type of SPI where the SDI is omitted.
Specifically on p11 they show the data being clocked out as 16 bits but then they show a 24th clock pulse ?
Why does it need 24 clock pulses to read 16 bits? No idea.

Is the clock supposed to run continuously or like SPI only when data is read?

So far, I am lost and unsure if I can even graft that onto my MPU with SPI interface.

Best regards
X

 

[stenzer]

Hi,

this kind of interface has to be implemented by yourself, and is not like an SPI or I²C interface, where the Master (MCU) is requesting a read by sending a read-command and which register shall be read out. Here you simply clock out the result register, and depending on the state of the clock line (and numbers of clock cycles) you can perform a calibration of the ADC or put it into sleep mode.

The shown 24th clock cycle and especially the 25th are shown how to change the ~RDY/DOUT pin back to its IDLE HIGH state, which will change to LOW again if data is available. So you can start again clocking out the new data.

BR

 

[Kripton2035]

you can look at an arduino library for this chip to figure out how it works.

GitHub - ae-michu/MAX11254-LIB: Library for MAX11254 ADC.

Library for MAX11254 ADC. Contribute to ae-michu/MAX11254-LIB development by creating an account on GitHub.

github.com

 

[KlausST]

Hi,

when I see such questions .. I ask myself: why did you chose this part?

What I mean: with my applications, I first decide my requirements .. then look for devices that meet my requirements.
Thus If I need a device with SPI interface .. I just do it using their selection guide .. and never would get a non_SPI recommendation.

However. It is what it is: A serial interface using two wires.
As far as I can see this is just a shift register. It should be easy to be implemented as SPI device, but it needs external hardware.
* 2-input NOR: IN1: SPI_CS_n, IN2 = SPI_SCK, OUT = MAX11254_SCK
* Driver with output_enable: IN=MAX11254_DOUT, EN_n = SPI_CS_n, OUT = SPI_MISO

I did not test it, nor did I do a timing analysis. Maybe one needs to invert signals. So please take this just as a raw idea.


Klaus

 

[userx2]

Hi,

when I see such questions .. I ask myself: why did you chose this part?

What I mean: with my applications, I first decide my requirements .. then look for devices that meet my requirements.
Thus If I need a device with SPI interface .. I just do it using their selection guide .. and never would get a non_SPI recommendation.

Klaus

Well...
The original requirement was for 4 sensors and it has changed to 5 sensors this week.
The original ADC chip, LTC2451 (I2C) works nicely with the original requirement but is too slow for 5 sensors.
So a faster chip is required in a similar physical size, reasonable price and not using extra CPU pins as I only have 2 spare pin.

Upon inquiring with all possibly supplier we have, there is nothing out there except this chip and one other, which is really expensive at $10+ as it is a successive approximation type. And neither use I2C nor normal SPI.

Regards
X

--- Updated Jan 8, 2025 ---

you can look at an arduino library for this chip to figure out how it works.

GitHub - ae-michu/MAX11254-LIB: Library for MAX11254 ADC.

Library for MAX11254 ADC. Contribute to ae-michu/MAX11254-LIB development by creating an account on GitHub.

github.com

From the DS, the MAX11254 chip has a proper SPI implementation so it is not compatible here.

Best regards
X

 

[KlausST]

Hi,

Upon inquiring with all possibly supplier we have, there is nothing out there except this chip and one

Farnell lists 100+ ADCs with I2C interface and 14+ bits resolution.

Usully there are even more with SPI interface....

Cheap, small, multiple channels ... everything is available. But you find only one ... an this is an expensive one without standard interface.
I wonder..

Klaus

 

[userx2]

Hi,

Farnell lists 100+ ADCs with I2C interface and 14+ bits resolution.

Usully there are even more with SPI interface....

Cheap, small, multiple channels ... everything is available. But you find only one ... an this is an expensive one without standard interface.
I wonder..

Klaus

Klaus, just because you can see stuff on Farnell, does not mean I can design it into a circuit here.
Think outside the box man, not everything works for everyone like you are used to.


Regards
X

 

[stenzer]

What are your actual design constrains? So far we only know/assume you need

• 5 ADCs
• 16 Bit resolution (?)
• I²C interface (even SPI is not usable as you only have 2 spare pins; except by using a multi channel ADC)

Questions

• what are your space limitations?
• price target?
• Required data update rate?
• minimum ADC sample rate?
• actual required resolution?

BR

 

[userx2]

What are your actual design constrains? So far we only know/assume you need

• 5 ADCs
• 16 Bit resolution (?)
• I²C interface (even SPI is not usable as you only have 2 spare pins; except by using a multi channel ADC)

Questions

• what are your space limitations?
• price target?
• Required data update rate?
• minimum ADC sample rate?
• actual required resolution?

BR

Thank you BR.

Well, ok, I need:
1 ADC chip 1 channel, single ended. (I use it to sample 5 circuits via a multiplexer).
16bit resolution.
100SPS min.
No more than 3 wire serial interface. I can accommodate I2C and SPI but have no additional spare pins available for a SPI nCS and IRQ/Ready
Single 3V3 operation, no additional power for reference and core voltage etc. as I have no space for generating that.
Preferably one shot capability so I can trigger the ADC conversion once the multiplexer has been set.

I think I can fit up to 6.3 x 4mm overall footprint size.

Best regards
X

 

[KlausST]

You come across quite condescending often in you replies

It´s not meant condescending .. I just use the informations you gave. This is ADC, I2C, cost .. you gave not much more. And with this - your - informations I did a part search. And found 100+ .. on one single distributor.
What exacly did I wrong? Did I have more informations to work with? Was it wrong to say that Farnell has 100+ parts that meet your given requirements?
What exactly do you call "condescending"?

From your given information ... it made no sense to chose exactly this ADC.

For sure you can blame it on me that you only give your informations at post#9.
If you ask for assitance ... and have requirements and specifications ... don´t hide them. We have no crystal ball.

"Think outside the box". If this means to "not stay focussed" ... then no. I do decades of electronics design .. with almost zero redesign. No handstands to design in unsuitable random devices. No, I don´t want to waste my time.

****

But to give some hopefully "useful" information:
In post#9 we can read that you want an ADC with a MUX in front of. Still you chose a delta-sigma ADC. But many delta-sigma ADCs are not suitable to MUX input signals. The digital signal of these ADCs takes a lot of samples to settle. And if you do multiplexing then you most probably get a lot of channel crosstalk.

I you want to use multiple channels, then there are multi chanel ADCs even delta sigma ones ... with simulataneous sampling or special MUXing techniques .. or use a SAR ADC - which don´t suffer from the huge digital value settling time problem.

Klaus

 

[userx2]

I am aware of the limitations of Delta Sigma in this case.

 

[stenzer]

What are you multiplexing? The digital interface or the analog inputs? Based on the informations in post #5, I would assume the digital interface.

Have a look on the AD7689 it hosts 8 ADCs in as single package, is cheaper than 5 pcs of MAX11205 and has a 4 wire interface (-> I²C + 2 Spare pins). Size wise it comes in a LFCSP package with 4 mm x 4 mm.

BR

 

[userx2]

Thank you.

As mentioned, I have 1 ADC channel and chip so the analog signals are multiplexed.

Except for the price and long lead times, that chip could work. I would have to re-design and eliminate one of the multiplexers.
Remains to be seen if that would fit into the limited space I have.

Regards
X

 

[BradtheRad]

compatible with "with the 2-wire interface"

The IC you looked at sends digital data. What's to stop you from finding its output on one or other line?

"2-wire interface" sounds like a simplest possible serial hookup. It reminds me of a 'null modem' cable I used for transferring entire files from a computer of one brand to another computer of a different brand. Even though it was the era of 9-wire interfaces, the 2 wires worked because data only went in one direction. No need for 'ready to send' or other handshaking signals. I kept active a program on the receiving computer (Macintosh), then commanded the sending computer to List or Type to its communications port.

 

[userx2]

What are you multiplexing? The digital interface or the analog inputs? Based on the informations in post #5, I would assume the digital interface.

Have a look on the AD7689 it hosts 8 ADCs in as single package, is cheaper than 5 pcs of MAX11205 and has a 4 wire interface (-> I²C + 2 Spare pins). Size wise it comes in a LFCSP package with 4 mm x 4 mm.

BR

I designed this into my circuit and another prototype flavour PCB today.
Just to see how it will work in the circuit and firmware.
But the price tag will likely put a stop to it since it is almost the same as the target cost of the unit. I will task our supplier to see if the price for it from Analog Devices can be squeezed. I doubt it will get cheap enough.

I also have another PCB on order using the MAX11205. I will figure out later how exactly to talk to it.

Best regards
X

 

[danadakk]

Just for future reference this family has configurable logic, and multiple copies of the elements below
in the part.

Routable internal and out to pins, includes basic logic, LUTs, and all the rest. Your design I think could be HW only, codeless*
Note I think for this particular design no small package is available, in general there is lots of I/O, hence driving pinout and
package size.

IDE (PSOC Creator) and compiler free. Excellent eval boards start @ $15.


Regards, Dana.

* Codeless designs you wire up HW, hit build button, and some config code auto generated.
But no user code under certain circumstances. Depends on what you are doing.