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TPS650860EVM-116: The IRQB pin function

Shih Scott
Prodigy 70 points
Part Number: TPS650860EVM-116
Other Parts Discussed in Thread: TPS650864

Hi

We are testing the TPS650860EVM-116 IRQB pin function. Below is my test step:

  1.  Wire a 2.2 ohm on Buck6 output and GND connector.
  2.  Change the R48 of the TPS650860EVM-116 component from 12.1K ohm to 330ohm. according to the formula of the datasheet of the SWCS142 my threshold should approach 0.188A. ("Rlim" can adjust the overcurrent threshold, and my max value of RDSON is 8.4mohm, ignore the Iripple.)    
  3. Program TPS650860EVM-116 Buck6 output voltage in 1.5V, and thrn on the CNTL pin.
  4. Output current should approach 0.681A, then IRQB pin active.

According to the datasheet of the TPS650864, IRQB should be active when Buck1、2、6 power fault or overcurrent, But it's can't work. 

I have a few quation below:

  1. Is my experiment correct, if I am not setting it wrong?
  2. Did I have another approach to test IRQB pin?

 

  • 0
    Prodigy 70 points

    Additional description:

    The IRQB pin in the experiment always pulls high. It should pull low when IRQB turns on.  (This pin is open-drain, according to schematic D5 should turn on when IRQB turns on.)

  • 0 in reply to Shih Scott
    TI__Mastermind 26385 points

    Hello,

    Thanks for reaching out! Our customer support team is unavailable Monday and Tuesday October 17-18th due to all-day workshops. Please expect a delayed response. Thank you for your patience.

    Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    TI__Mastermind 26385 points

    Hello, 

    Apologies for any inconvenience due to the delay in response. Please see my comments in regards to your questions below. 

    1) Yes, in theory your experiment is correct. Forcing an overcurrent by lowering the current limit should produce a fault. The reason you do not observe the IRQB pin go low may be because the fault interrupt is default masked on the TPS650860EVM-116.

    I recommend checking IRQ_MASK register (address 03 hex) and ensure the interrupts are unmasked then attempt your test again. 

    2)An alternative approach to test IRQB pin is to simply turn off then turn back on the input power supply to the EVM. I have confirmed on an TPS650860EVM-116 in lab that upon turning power back on and unmasking the shutdown interrupt the IRQB pin goes low and remains low until you acknowledge the interrupt by writing to SHUTDNSRC register (address 05 hex) and IRQ register (address 02 hex). 

    Let me know if you can observe IRQB function correctly after unmasking the fault interrupt or if you have any further questions. 

    Best Regards,

    Garrett

  • +1
    Prodigy 70 points

    Hi, Garrett

    Appreciate the reply, I follow the step unmask register, but the result wasn't expected. I set the register 03h to unmask the fault interrupt, but the register wasn't turned on in 02h & 05h, even the Buck6 OCP for B6h wasn't pulled high.

    I tried another approach for unmask shutdown interrupt it's all correct just like you said.

    So I thought are there have anoter register could influence the OCP?

  • 0 in reply to Shih Scott
    TI__Mastermind 26385 points

    Hello, 

    Good to hear you observed IRQB function properly when using the alternate shutdown approach. 

    Shih Scott said:
    So I thought are there have anoter register could influence the OCP?

    There is no other register on the device that influences the OCP. If you wish to further debug why you are not observing OCP would you be able to provide a waveform of the BUCK6 output voltage, as well as, measure the current across your resistor load to verify the BUCK6 operation conditions.   

    Regards,

    Garrett

  • 0
    Prodigy 70 points

    Hi, Garrett

    Thanks for help. About OCP experiment, I figure out the problem that OCP can't be detected because my load resistor was overload. I changed power rating of resistor  from 1/16W to 50W, then OCP was detected, the problem was solved. I still have another quation, over the test my Buck6 output voltage is 1.5V but when my OCP was detected meanwhile output voltage down to 0.85V, then I changed value of the Rlim from 330ohm to 12.1kohm, the output voltage backed to 1.5V. Why the phenomenon was happened? 

  • +1 in reply to Shih Scott
    TI__Mastermind 26385 points

    Hello, 

    The overcurrent protection leads to the output voltage dropping as a response to the current being limited. This is briefly described on datasheet page 65 and shown below. When the current limit is raised up by changing Rlim the voltage is able to return to normal regulation.

    Best Regards,

    Garrett

  • 0
    Prodigy 70 points

    Hi,

    Appreciate your help. My question was all solve.