Hi,
Let me talk about the using TCA9801.
I got two questions from customers.
① B-side has internal current source. Therefore, a pull-up resistor is not required.
Is there a problem when the pull-up resistor is installed outside the TCA9801?
Customers want to know the risk of the case of installing the pull-up resistor added.
② Is it OK to use either A-side or B-side as Master?
Could you give me your advice?
Best Regards,
Yusuke/Japan Disty
Hello Yusuke-san,
1) The TCA9801 is designed to be used without pull up resistors on the B side. It can withstand some leakage current that could be from a pullup resistor and is defined as IEXT-I. As long as you stay within that leakage current then you will not affect the device operation with determining the logic state of that pin.
Here are some examples of the min pull up resistance that is needed to make sure the device operates properly. Keep in mind that there can be other leakage paths outside of the pull up resistor.
2) There is no requirements on which side can be connected to the master. The part has no idea which side the master is on and it doesn't care. I2C is a bidirectional protocol.
Let me know if this answers your question and if you have any other questions let me know. Please hit the "Resolved" button if I have answered your questions.
Sincerely,
-Francis Houde
