Thermal hysteresis is measured with the REF70 soldered to a PCB, similar to a real-world application. Thermal hysteresis for the device is defined as the change in output voltage after operating the device at 25°C, cycling the device through the specified temperature range, and returning to 25°C. This can be seen in Figure 8-6 to Figure 8-8. Hysteresis can be expressed by Equation 1:

Equation 1.

where

• V_HYST = thermal hysteresis (in units of ppm)
• V_NOM = the specified output voltage
• V_PRE = output voltage measured at 25°C pre-temperature cycling
• V_POST = output voltage measured after the device has cycled from 25°C through the specified temperature range of –40°C to +125°C and returns to 25°C.

Figure 8-6 REF7025QFKHR Thermal Hysteresis Distribution (-40°C to 125°C)

Figure 8-8 REF7012QFKHR Thermal Hysteresis Distribution (-40°C to 125°C)

Figure 8-7 REF7012QDGKR Thermal Hysteresis Distribution (-40°C to 125°C)