I2C A/D Converter in DIP package

[VirusX2]

I'm looking for I2C A/D converter in DIP package with 65kSPS minimun sampling speed. I can't find anything. Is there anyone..?

 

[FvM]

That's impossible with standard (100 kHz) and fast (400 kHz) I2C data rate. So you'll hardly find any I2C AD C with similar speed, neither DIP nor SMD.

 

[VirusX2]

With SOT package i found this: https://www.ti.com/product/adc121c021
It is at 189 kSPS, I2C, but it's difficult to handle sot packages, i prefer DIP.

 

[ArticCynda]

I'd recommend you to go for the SOT ADC and solder it on a breakout board to "convert" it to a DIP version. You can then test the operation of your circuit at a lower sample rate, i.e. 10 kHz for example.

 

[bigdogguru]

With SOT package i found this: https://www.ti.com/product/adc121c021
It is at 189 kSPS, I2C, but it's difficult to handle sot packages, i prefer DIP.

Please review the datasheet, the maximum sample rates of the ADC121C021 are list in the A.C. and Timing Characteristics Table, Conversion Rate, Page 8:



A sample rate of 189 kSPS requires a I2C clock frequency of 3.4 MHz.

The sample rates for 100 kHz and 400 kHz clock frequencies are 5.56 kSPS and 22.2 kSPS respectfully.

While you've not mentioned the required resolution, even at 8 bits, it's exceedingly difficult to cram 65 kilobytes per second down a synchronous serial bus with only a 400 kHz clock, even without considering any overhead.

You would have better luck searching for an ADC in a DIP package with an SPI or parallel interface for your sample rate requirements.

Maxim offers a few ADCs with an SPI and parallel interfaces which could fulfill your sample rate requirements.

Also, you might want to specify what will be controlling the ADC.


BigDog

 

[VirusX2]

Please review the datasheet, the maximum sample rates of the ADC121C021 are list in the A.C. and Timing Characteristics Table, Conversion Rate, Page 8:



A sample rate of 189 kSPS requires a I2C clock frequency of 3.4 MHz.

The sample rates for 100 kHz and 400 kHz clock frequencies are 5.56 kSPS and 22.2 kSPS respectfully.

While you've not mentioned the required resolution, even at 8 bits, it's exceedingly difficult to cram 65 kilobytes per second down a synchronous serial bus with only a 400 kHz clock, even without considering any overhead.

You would have better luck searching for an ADC in a DIP package with an SPI or parallel interface for your sample rate requirements.

Maxim offers a few ADCs with an SPI and parallel interfaces which could fulfill your sample rate requirements.

Also, you might want to specify what will be controlling the ADC.


BigDog

Thanks for your answer! The ADC will be controlled by PIC18F4553. I want 1 ADC minimum to 6 ADCs maximum running simultaneously. So you suggest me to build my system around SPI protocol? What's the maximum speed i can reach with my PIC in SPI? And a last thing, can i have hot-plug with SPI? E.g to disconnect an ADC and microcontroller catch it like ACK on I2C?

 

[bigdogguru]

The ADC will be controlled by PIC18F4553. I want 1 ADC minimum to 6 ADCs maximum running simultaneously. So you suggest me to build my system around SPI protocol? What's the maximum speed i can reach with my PIC in SPI?

The PIC18F4553 is actually a PIC18F4550 variant, therefore reference the PIC18F4550 datasheet:

Reference: PIC18F2455/2550/4455/4550 Datasheet, Section: 19.3.5 SPI MASTER MODE, Page: 202

In Master mode, the SPI clock rate (bit rate) is user-programmable to be one
of the following:

• Fosc/4 (or TCY)
• Fosc/16 (or 4 • TCY)
• Fosc/64 (or 16 • TCY)
• Timer2 output/2

This allows a maximum data rate (at 48 MHz Fosc) of 12.00 Mbps.

Therefore while the SPI protocol utilizes the same MSSP module of the PIC18F4550, the maximum data rate of SPI far exceeds that possible of the I2C protocol, 1MHz Maximum Clock Rate, on the same device. Also the number of devices on a specific SPI bus is only limited by the number of chip select (CS) lines available on the microcontroller or an external addressing system.

And a last thing, can i have hot-plug with SPI? E.g to disconnect an ADC and microcontroller catch it like ACK on I2C?

Possibly, however I have not personally implemented a "hotplug" feature on either I2C or SPI bus of a PIC18F microcontroller, therefore cannot advise you in that area. The SPI is also a synchronous serial protocol, however it utilizes a chip select line to select which device on the SPI bus the master initiates communication.


BigDog

 

[VirusX2]

Therefore while the SPI protocol utilizes the same MSSP module of the PIC18F4550, the maximum data rate of SPI far exceeds that possible of the I2C protocol, 1MHz Maximum Clock Rate, on the same device

So can i achieve 1 MHz clock speed with I2C with my PIC (running at 20MHz) ?