ensure the output impedance of the filter does not degrade ac performance. This can occur in RC low-pass

filters where a large series resistance can impact the load transients due to output current fluctuations.

Frequency (Hz)

0

10

20

30

40

50

60

70

80

90

100

10

100

1k

10k

100k

Figure 8-10. Noise Performance 10 Hz to 100 kHz

8.5 Temperature Drift

The REF70 is designed and tested for a minimal output voltage temperature drift, which is defined as the

change in output voltage over temperature. Every unit shipped is tested at multiple temperatures to ensure that

the product meets data sheet specifications. The temperature coefficient is calculated using the box method

in which a box is formed by the min/max limits for the nominal output voltage over the operating temperature

range. REF70 has a low maximum temperature coefficient of 2 ppm/°C from –40°C to +125°C. This method

corresponds more accurately to the method of test and provides a closer estimate of actual error than the other

methods. The box method specifies limits for the temperature error but does not specify the exact shape and

slope of the device under test. Due to temperature curvature correction to achieve low-temperature drift, the

temperature drift is expected to be non-linear. See SLYT183 for more information on the box method. The box

method equation is shown in Equation 2:

REF(MAX)

REF(MIN)

6

REF(25 C)

V

V

Drift

10

V

Temperature Range

q

§

·

u

¨

¸

¨

¸

u

©

¹

(2)

Temperature (°C)

-50

-25

0

25

50

75

100

125

2.499

2.49925

2.4995

2.49975

2.5

2.50025

2.5005

2.50075

2.501

Figure 8-11. Output Voltage Vs Free-Air Temperature

8.6 Power Dissipation

The REF70 voltage references are capable of source and sink up to 10 mA of load current across the rated

input voltage range. However, when used in applications subject to high ambient temperatures, the input voltage

and load current must be carefully monitored to ensure that the device does not exceeded its maximum power

dissipation rating. The maximum power dissipation of the device can be calculated with Equation 3:

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REF70

SNAS781D – OCTOBER 2020 – REVISED DECEMBER 2021

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