# TPS26601 Industrial eFUSE Circuit Design

I have been designing a circuit for various Power protections like overcurrent, overvoltage, undervoltage, reverse input polarity. I have selected Industrial eFUSE TPS26601. I have few queries regarding the circuit designing for TPS26601.

1. I am using a switch to pull-down SHDN pin for shutdown and leave it floating for normal operation as Page 25 of the datasheet shows an internal pull-up resistor. Am I correct?
2. I know how to connect RTN pin of the IC but I am not sure why it has been there. The datasheet says it is for Device's Internal Reference. Why can't they have single pin (use GND for Device Internal Reference)?
3. The Imon pin of the IC is referred w.r.t to RTN pin. Imon pin outputs a current proportional (Reduced by certain factor) to current flowing through OUT pin. Connecting a resistor across Imon and RTN pin can convert the current to voltage and external ADC can calculate the system current. Since, Imon resistor is connected w.r.t RTN pin, I am not sure about using opto-coupler. Should I use it? Is it safe to connect directly to MCU?
• 1. If the datasheet shows a pullup, it's probably adequate unless you're in a high noise or high EMI environment. 2. Sometimes you want a reference ground that has very little current flowing; the potential of your power ground might vary based on instantaneous current. 3. If your MCU and chip are using the same ground and the voltages are compatible, it should work without an optocoupler. – Cristobol Polychronopolis Dec 11 '18 at 14:12
• The MCU will be using GND and TPS2660x will be using RTN. – abhiarora Dec 11 '18 at 14:14
• Then it should work, just make sure the output is scaled to within the ADC range. The RTN pin on that chip is the same as ground if you hook the supply up correctly. – Cristobol Polychronopolis Dec 11 '18 at 14:19
• @CristobolPolychronopolis Thanks. You can change the comment to an answer and i will accept it. – abhiarora Dec 21 '18 at 7:53