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TPS7B7702-Q1: /ERR pin question

Peter Xu
Expert 6000 points
Part Number: TPS7B7702-Q1

Hi team,

My customer wants to use TPS7B7702-Q1 to output 2 supply rail. However, they do not have much ADC resource, they do not want to connect the sense pin to ADC.

Now they only want to know the short circuit fault. They connect these two rails to different loads, and they need to know which load has a short circuit problem when /ERR is pulled down. If they just connect the /ERR pin to GPIO, they can only know when the short circuit happens, but they want to know which output rail has a short circuit problem. Is it possible? 

From the datasheet, I can only know that /ERR pin triggers when any rail has a short circuit problem. Can I identify the exact rail by GPIO? For example, I set the Rsense to a small value, like 1k ohm. Then, when in normal status, the sense output should be 1V(200mA output). In 3.3V GPIO logic, it should be a low-voltage. And when in short circuit, it changes to 2.4V, it should be a high-voltage in 3.3V GPIO logic. Is it feasible?

Regards,

Peter

  • 0
    TI__Mastermind 37005 points

    Hi Peter,

    By toggling the SENSE_SEL pin the customer can evaluate the current from both LDO's combined, and also the LDO2 only.  They can use subtraction to calculate the current out of LDO1 as a result.  This will enable them to determine which LDO is exceeding the current limit. 

    Thanks,

    Stephen

  • 0 in reply to Stephen Ziel
    TI__Expert 6000 points

    Hi Stephen,

    I draw a picture about the detection, can you check if I am right?

    Regards,

    Peter

  • 0 in reply to Peter Xu
    TI__Mastermind 37005 points

    Hi Peter,

    The table in red / white looks "correct" but the way you are describing the logic as a low / high is not entirely accurate for the sense voltage.  Please see section 7.3.1 in the datasheet.  The sense voltage "high" depends on the fault being described (short circuit and current limit, thermal shutdown, reverse current and short to battery).

    Thanks,

    Stephen