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TPS2H160-Q1: Reverse Current Protection

John Fedak
Expert 6715 points
Part Number: TPS2H160-Q1
Other Parts Discussed in Thread: TPS1H100-Q1

Hi Team,

Good morning, one of my customers is using the TPS2H160-Q1 in their design and when using the 1k resistor in parallel with a 1N4148W diode, the input voltage relative to ground is exceeding the rating of -0.3V. With this, how should they implement the reverse voltage protection scheme where an MCU is intended to connect the input pins to ground without violating the abs max rating?

More info from the customer -----------

We are using the TPS2H160BQPWPRQ1 in a current design and have discovered a couple issues when installing the reverse polarity protection diode and resistor pair at ground. Our circuit snippet is as follows:


 

We are using the reverse current protection in Figure 25 of the datasheet.

First, we initially used a 1k resistor in parallel with a 1N4148W diode. The 1k is sugested on the datasheet, page 23. We observe a forward voltage of 0.33V across this diode. Since INx pins may be grounded (THER is grounded by default), the input voltage relative to ground exceeds the minimum rated value, -0.3V. When powered, the driver does not drive a load, and we saw 30mV with respect to circuit ground at the CL pin.

 

When we modified CL to connect to the GND pin of the device, rather than the circuit ground, the device output works. We have discovered this in our validation testing, however, we did not see any note of it in the datasheet or SLVA859 current limitation document.

-------------------------------------------------

Thank you!

Regards,

~John

  • 0
    TI__Mastermind 28200 points
    Hello,

    That is right. The pull down resistor on CL pin must be connected to device ground pin and not to network ground.
    TPS1H100-Q1 (SLVSCM2B) datasheet shows that in figures 40 and 42. The TPS2H160-Q1EVM (SLVUAS9) shows that the Rcl is also connected to device ground as well.

    Regards
  • 0 in reply to Mahmoud Harmouch
    Prodigy 10 points

    Thank you for your response. This configuration still appears to violate the absolute maximum rating of the input pins. How do we prevent going outside of the datasheet values? Here is the concerning scenario:

    We are measuring 0.33V from the device ground to board ground. That means that if we ground any other inputs to board ground we will violate the absolute max ratings of the device (-0.3V). This is in normal operation. A WCCA approach means that we would likely be way out of spec. Here is a sketch showing how I am measuring the ground offset (black), and the input potentials (red):

     

     

  • 0 in reply to Andrew S
    TI__Mastermind 28200 points
    I understood your concern and agree with that the absolute max -0.3V seems to be violated. In reality it is not right. There is no issue on these pins as long as the ground shift is less than 0.6V. The -0.33V should not cause any problem.

    Regards