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TL432B: shunt reference WCCA discussion

Part Number: TL432B

I do not need a very precise reference power supply, but also to reduce costs. TL432B is a better option.

1. Without calibration and the TL432B REF pin connects to CATHODE, operating temperature from -40oC to +125oC, the maximum output VKA is max. of Vref plus max. of VI(dev), which becomes 2507mV+34mV=2541mV, right?

2. If question 1 is correct, should I add additional deviation came from the effect of temperature coefficient aVref into the maximum output of TL432B calculation?

3. If operating temperature is -40oC to +105oC, the maximum output VKA is 2507mV+ [(105oC-25oC)*34ppm/oC]*2495mV=2507mV+6.786mV= 2513.8mV, is that correct?

  • Hi User,

    which precision of output voltage do you need?

    Kai
  • Hi Wilson,

    My answers below in blue.

    1. Without calibration and the TL432B REF pin connects to CATHODE, operating temperature from -40oC to +125oC, the maximum output VKA is max. of Vref plus max. of VI(dev), which becomes 2507mV+34mV=2541mV, right?

    The calculation you used is to find the maximum deviation of the TL432BQ in the closed loop configuration when the Vref is directly shorted to Vka as shown in section 4 of the datasheet. In this situation it is as you described, the Vka will vary with accuracy and temperature. In the worst case the Vref will be as you calculated above. The opposite is also true where the Vref can go low and the output value can be 2483mV - 34mV = 2449mV.

    2. If question 1 is correct, should I add additional deviation came from the effect of temperature coefficient aVref into the maximum output of TL432B calculation?

    The value boundaries calculated above can be used as the Vref value for Vka = Vref (1 +R1/R2) + Iref * Ref. There is also other factors for calculating the most accurate Vka that are outlined in this app note

    Setting the Shunt Voltage on an Adjustable Shunt Regulator

    3. If operating temperature is -40oC to +105oC, the maximum output VKA is 2507mV+ [(105oC-25oC)*34ppm/oC]*2495mV=2507mV+6.786mV= 2513.8mV, is that correct?

    No, this is where understanding how the temperature coefficient is calculated. The temp co is calculated using the box method. More details  are in the document below:

    Voltage Reference Selection Basics

    But essentially we guarantee the maximum worst case deviation but we don't guarantee where it occurs so even if you use a smaller temperature range, the maximum temp co deviation would still be the same as the full temperature range.

    -Marcoo