This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: ISO1541
In customer’s test, when SDA1 is output, the output low level rail is not zero, about 0.7V.
Checked datasheet, there is a diode between the MOSFET source and GND, so this 0.7V is the diode voltage drop.
Now, customer concern that 0.7V is around the low level threshold of CPU, so the I2C communication maybe wrong in some cases.
Why connect this diode? Why not connect MOSFET source to GND directly?
Thanks for posting on E2E. The explanation for this is posted in Section 8.4 of the datasheet. (pages 19 and 20). For convenience, I am quoting the relevant section directly below.
Isolator Functional Principle (continued)
At first sight, the arrangement of the internal buffers suggests a closed signal loop that is prone to latch-up. However, this loop is broken by implementing an output buffer (B) whose output low-level is raised by a diode drop to approximately 0.75 V, and the input buffer (C) that consists of a comparator with defined hysteresis. The comparator’s upper and lower input thresholds then distinguish between the proper low-potential of 0.4 V (maximum) driven directly by SDA1 and the buffered output low-level of B.
Please let us know if you need additional clarifications.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.