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TPS79928 Minimum Output Load in Datasheet

Teik Hooi Teoh
Intellectual 655 points
Other Parts Discussed in Thread: TPS799

Hi,

In datasheet section 8.2.2.5 Minimum Load, there is a description:

The TPS799 is stable with no output load. To meet the specified accuracy, a minimum load of 500 μA is required. With loads less than 500 μA at junction temperatures near 125°C, the output can drift up enough to cause the output pulldown device to turn on.

It seems to be confusing as it states stable without output load, but then there is a need of minimum 500uA for accuracy but at the expense of possible forced turn on.

We are interested in this as we encountered a leakage in the output before the EN pin is asserted HIGH. During that time, the output load cicruit is open.

Please help to enlighten. Thanks.

  • 0
    TI__Expert 3910 points

    Hi Teik,

    TPS799 is indeed stable with no output load, however there is a couple things to keep in mind:

    1. "To meet the specified accuracy, a minimum load of 500 μA is required." 
      This refers to certain parameters you will find throughout the datasheet, for example IGND is said to have a typical value of 40 μA and a maximum of 60 μA. This parameters are assuming a minimum load of 500 μA. (some examples below).

      Source: TPS799 Datasheet (TI Document ID: SBVS056K)

    2. "With loads less than 500 μA at junction temperatures near 125°C, the output can drift up enough to cause the output pulldown device to turn on."
      This refers to a specific case where your junction temperature is near the upper end of the devices operating temperature range (-40°C to 125°C), this situation is unlikely to happen because at 500 μA and your operating voltage 2.8 V you would be only at 1.4 mW, meaning the contribution to the junction temperature from heat dissipation from your device would be less than 1°C. This issue would arise if your ambient temperature is nearing 125°C.

    Also, certain leakage is expected from our device, this is specified as "Shutdown Current", ISHDN and can be found in the datasheet udner the Electrical Characteristics table.

    Best Regards,
    Victor