REF195 SERIES [REF195] : Min/Max voltage output.

Hi,

Based on the datasheet, ELECTRICAL CHARACTERISTICS—REF195 @ TA = 25°C,  the output voltage will change only between  4.990 and 5.010 on Grade G.

I couldn't find any related data around how to calculate or recognized, how the output varies based on the application or Vs input voltage.

If I assume that the output voltage is independent of Vs input voltage or/and the circuits around the REF195 then the output voltage always should be in the range of 4.990V and 5.010V.

The issue comes as to why I have a solid  4.975v as the output. It is important in my calculation to see how the output could vary and what is the tolerance on it. (the min and max) or what is the formula that I can calculate the tolerance/accuracy on the output voltage?

In my Board, I am using "CURRENT-BOOSTED REFERENCES WITH CURRENT LIMITING" circuit with Vs =12V and the output that I am getting is solid 4.97V. (REF195GSZ)

Could you please help to understand the output voltage behavior more in detail?

Thank you

  • 0
    •  Analog Employees 
    on Nov 15, 2019 6:25 AM

    Voltage Reference unit Output shift:
    1. Initial Accuracy
    -> 4.990V to 5.010V
    2. Line Regulation
    ->4ppm/V to 8ppm/V

    (4ppm/V)/100000=0.0004%/V
    (0.0004%/V)/100=4u/V
    (4u/V)*5V=20uV/V

    %=deltaVout/Vout

    ->20uV/V to 40uV/V
    3. Load Regulation
    ->4ppm/mA to 8ppm/mA
    ->20uV/mA to 40uV/mA

    4 Solder Shift
    ->(-0.12%) to 0.05%
    ->(-6mV) to 2.5mV

    5. Mechanical Stress
    ->unspecified but should be accounted.

    Total Output Shift (w/o temp coeff) = Initial Accuracy + Line Regulation + Load Regulation + Solder Shift + Mechanical Stress
    TOSmaxpos = 10mV + (40uV/V)(Vin@pin2 - 5.1V) + (40uV/mA)(Ioutpin6) + 2.5mV + MS
    TOSmaxneg = 10mV + (40uV/V)(Vin@pin2 - 5.1V) + (40uV/mA)(Ioutpin6) + 6mV + MS

    This is the equation for Output Voltage Shift without considering the Temperature dependent variables and LTD.

    "Current-Boosted Reference with Current Limiting" circuit
    Things to consider:
    -This is tested but not fully specced.
    -There is consideration regarding output line Trace/Connection.
    " A short, heavy, low dc resistance (DCR) conductor should be used from U1 to 6 to the VOUT Sense Point S, where the collector of Q1 connects to the load, Point F."
    -Output Line Resistance(R6S-Resistance from pin6 to S) will cuase additional drop in output voltage.