This latch-up prevention scheme is implemented in several popular I2C level shifting and bus extension products currently available from Analog Devices and other manufacturers. The Side 1 I/O pins must not be connected to other I2C buffers that implement a similar scheme of dual I/O threshold detection. In other words, Side 2 of the ADuM2250/ADuM2251 is I2C-compliant while Side 1 is only I2C-compatible. The thing that puzzled me at the time, and I still wonder if I got it right, is this statement from the data sheet, regarding the difference between side 1 and side 2:īecause the Side 1 pin has a modified output level/input threshold, Side 1 of the ADuM2250/ADuM2251 can only communicate with devices fully compliant with the I2C standard. The system power is 12V, and a separate 1W isolated DC-DC module provides isolated 12V for the ADC side of the ADuM225 and for the 4-20mA loop. One of those goes to a bridge sensor (Druck level meter) and the other to a 4-20mA device, both having to do with hydrology and cables that extend quite a distance to the measurement point, especially the 4-20mA. On one side is the ♜ and on the other side are two channels of 16 bit ADC, using the ADS1100. This was originally made for the BASIC Stamp 2pe (OWL2pe data logger), but I'd like at some point in time to modify it for the Propeller. I hope Don doesn't mind if I jump in on his thread while we have this I'm attaching a schematic of my ADuM2250 circuit. I may not have the big picture here, but it seems like since you have 3.3V available on each side, if you use the ADuM5201 you could just use the data channels directly. I am a little puzzled why you are buffering the signals with optocouplers when the ADuM5202 has isolated channels. My rule of thumb is limit the current to less than 1mA and you should be ok, but it might slow the input down. If damage occurs, it might not effect functionality, but you might eventually find that the ESD protection is gone. They are built to disipate ESD transients, but not continuous power, so they can be damaged by continuously running them with forward bias. When the input level is more than 1 diode drop above the VDD level, then it will forward bias one of these diodes. The ADuM5202 uses standard CMOS structure in its logic inputs, in particular it has ESD protection diodes that connect to VDD and GND. First, your question about the input voltage tolerance when running at 3.3V. I looked over your application and schematics. I am the ADI applications engineer that supports the isoPower devices. I am not sure of ADI's sample policies, TI seems even with the National merger, to be very liberal in their samples programs as well. Any possibility of sampling these devices? Probably Don would be interested in getting a couple to try in his development, and myself down the road if I ever get a grant to develop a semi invasive medical device. I have seen these chips as well as some similar from TI, the AVNET eNewsletter is a very nice resource (its free y'all) and the FAEs I have talked to are great resources as well. I may be looking at some ADI devices (A/D DAC 1-10Ms/s range) though mostly learning to use them with the prop. Hey, ADI, nice to know you are out there. I believe this may be a single part pricing and you should be able to do significantly better in volume. It looks like the community has given you some great advice but I wanted to respond to the pricing that you posted. I am from Analog Devices and responsible for this product.
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