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TPS73801-SEP: Worst Case Circuit Analysis using Extreme Value Analysis

Spencer Ford
Prodigy 10 points
Part Number: TPS73801-SEP

I am working on a worst-case circuit analysis using the extreme values analysis, and I am trying to understand how the variation in Vfb affects the voltage regulation.

In the datasheet, I see a max range of 1.174V to 1.246V. Below that, I see another section named "Load Regulation" that lists 18mV across the whole range. 

Should I be using the range of Vfb in the Vout equation (1) to determine min/max regulation? Or should I be using this "Load Regulation" metric? It is unclear to me what the "Load Regulation" means exactly in this context.

  • +1
    TI__Expert 8260 points

    Hi Spencer,

    If your goal is to understand the isolated impact of VFB variation on VOUT, then you could plug the min/max values into the VOUT equation as you suggested. 

    The load regulation specification described how much VOUT can vary due to load across the entire range of IOUT (1mA-1A).

    This post contains additional details that should help clarify the specs.

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    Prodigy 10 points

    Hi Sarah,

    Trying to understand how to interpret that 18mV number and this topic in general. 

    1) Does the load regulation specifically refer to the response to a load step, or does it imply that at 1A output the VOUT can differ by 18mV at a steady 1A load?

    2) Does the 18mV number mean either:

          a) Vout can change +-18mV based on output current? 

          b) The difference between the high and low Vout is 18mV based on output current?

          c) The largest voltage drop on a 1ma-1A load step is 18mV?

    I noticed the load regulation in Figure 6-19 changes from +4mV to -8mV which looks closer to the interpretation b?

    3) Is there a good way to get an estimate at smaller output currents? I did not see a chart for voltage regulation versus output current. 

    Thanks,

    Spencer

  • +1 in reply to Spencer Ford
    TI__Expert 8260 points

    Hi Spencer,

    I can help clarify.

    1. Load Regulation is a steady-state parameter that doesn't include peaks from transient events. Using your example, under maximum load (1A) the output voltage can differ from the no load condition by up to 8mV (max at 25C) or 18mV (across the full temp range). In reality, it is usually less than the maximums, but the max values are valid to use for a quick and more conservative WCA as long as they don't cause you to land outside of acceptable thresholds for your design. 

    2. Load Regulation typically indicates a negative change to VOUT given an increase in IOUT. Figure 6-19 shows the impact of temperature on this spec. 

    3. Unfortunately, we don't have data to conclusively say whether this spec is linear. 

    Thanks,

    Sarah