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TPS7B69-Q1: TPS7B6950QDBVRQ1

Pengpeng Li
Prodigy 30 points
Part Number: TPS7B69-Q1

Tool/software:

Hi TI support team，

I have created a case CS2614626 before and I still have some questions need to follow with you. 

Below introduced my request.

We have conducted a test that when we connect the 24V voltage to A point under 125degC, we measured the voltage on B point is 8V. We checked the reverse leakage current of Diode under 125degC is 2mA, so 24V will flow through Diode and pull up the voltage level on point B. We have tried replacing the diode with 4uA reverse current under 125degC to do short to battery test and there is no issue for the output of LDO. So, if we know the capability of LDO reverse leakage current, it will support us to do Diode selection. 

You have given me below reply last time.

It did help, thanks a lot. But it cannot support us to choose suitable diode to limit the reverse current flowing into LDO. Is that possible to help to do test or simulation to get the LDO reverse current capability? Please help to check and let me know if any unclear. Thanks.

Hi Pengpeng,

As mentioned in my earlier email, the max Vout for this device is 7V. So, setting the LDO Vout to 8V likely damaged the device and so the test results are not in line with expected.

Reverse leakage current and quiescent current are two separate current paths. You cannot use the attached figure to determine leakage current.

Upon checking, this part does not have internal reverse current protection, we don't spec out the max reverse leakage current. A good rule of thumb is to limit it to less than 5% of the Iout which would be 7.5 mA.

  • 0
    TI__Genius 13490 points

    Hi Pengpeng,

    Please provide the value for VCC. If VCC < VOUT (8V in your case), the reverse current will flow through the body diode of the Pass FET in the LDO. In this case, we advise limiting the reverse current to less than 5% of IOUT (7.5 mA). If VCC > VOUT, then the reverse current will flow through a pull-down resistor internally in the device and you may be able to sink a little more current. 

    However, abs max on VOUT is still 7V. So please ensure that this rating is not violated.

    Regards

    Ishaan

  • 0 in reply to Ishaan Shetye
    Prodigy 30 points

    Hi Ishaan,

    Thanks for sharing these information. 

    VCC is 7.5V, so the reverse current will flow through the bode diode in the FET of LDO.  But the value of 7.5mA you provided is too much larger since this issue happened with 2mA reverse current based on the spec of Diode. There is no issue with 4uA reverse current. But the diode with 4uA reverse current (under 125degc) is hard for component selection. So could you please help to check is there other method like test or simulation to get more accurate reverse current capability for the LDO? Thanks.  

  • 0 in reply to Pengpeng Li
    TI__Genius 13490 points

    Would you be able to spec a diode with 100 uA of reverse current? If so, that would be comfortably within the limits of the device and give you a good component selection.