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TPS798-Q1: Need Vout variation with temperature, preferably in ppm/ºC for TPS79801-Q1

Walter Rothe
Prodigy 40 points
Part Number: TPS798-Q1

We are thinking about replacing the LT1761 with the TPS79801-Q1 by tying pin 2 to pin 3 and some BOM changes. There is a graph of Line regulation versus temperature, but only can find an absolute 3% variation of the reference voltage over a number of different terms. Our load and line changes are not that important, but variation with temperature is. Do you have any value for Vout variation in ppm/ºC or a graph?

  • 0
    Prodigy 40 points
    We are replacing the LT1762, not the LT1761
  • 0 in reply to Walter Rothe
    TI__Guru 55940 points

    Hi Walter,

    Figure 2 provides the closest information to what you are looking for.  At 30 Vin, we see a spread of ~0.650 mV over a range of 125 C.  This would yield ~5.2 ppm/C.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 40 points

    That is the way I first looked at it also, but after further thought, line regulation is the change in Vout over the change in Vin. It is a short term pulse that is applied. The fact that it is done at a lower temperature and then again at a higher temperature doesn't mean it is also telling you about the change in Vout when the temperature went up, in between. Is there not some other data that you have on this?

  • 0 in reply to Walter Rothe
    TI__Guru 55940 points
    Hi Walter,

    I think you may be confusing line regulation (DC spec) with transient response (AC). Line regulation is a slow sweep on the input voltage while measuring the output voltage. This allows us to see how the output varies with regards to different DC input voltages. The same slow sweep on input voltage is run on the same units over the three temperatures.

    We do not directly measure how the output of an LDO drifts with regards to temperature in the way you are wanting.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 40 points
    Hi Ryan,

    Ok. My point though is that line regulation versus temperature, the way you do it, with a slow ramp, then changing the temp, then doing it again, misses the change in output voltage with temperature. The only way I can use your line reg vs temp is it might tell me that the change in output voltage due to temperature is worse than the curves you show. But 3% total error is much much higher than that. There is a lot that I could be missing. Other parts seem to give you some form of output voltage change versus temperature. I wish you would do that for that part.

    Best,
    Walter