REF3312_15 Datasheet, PDF (16/32 Pages) Texas Instruments – REF33xx 3.9-μA, SC70-3, SOT-23-3, and UQFN-8, 30-ppm/°C Drift Voltage Reference

REF3312, REF3318, REF3320, REF3325, REF3330, REF3333
SBOS392E – AUGUST 2007 – REVISED OCTOBER 2014
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f_{3dB _ A1}
1
2
˜
S
˜
§
¨©
R₆
2
·
¸¹
˜
C₂
0.144 Hz
(18)
In applications that cannot tolerate such a low-frequency cutoff, and therefore a long start-up time, buffer the A1–
input with another OPA317 to properly drive the ADC input with a lower-input capacitor.
10.2.1.2.7 Passive Component Tolerances and Materials
Resistors R₁, R₂, R₃, R₄, R₅, R₆, and R₇ directly affect the accuracy of the circuit. To meet the unadjusted
accuracy goals of 0.2%, the resistors used are 0.1%. Select 0.1% resistors for the construction of the difference
amplifier circuit to provide a common-mode rejection ratio (CMRR) of at least 60 dB.
10.2.1.3 Application Curves
10.2.1.3.1 DC Performance
The measured dc performance and calculated error of the circuit is shown in Figure 20 and Figure 21,
respectively. By applying a two-point gain and offset calibration over the specified ±5-V input range, the
calibrated error is shown in Figure 22. The uncalibrated results show errors of 138 μV, or 0.0138%FSR. The
calibrated results with a simple two-point calibration show errors under 5 μV, or 0.0005%FSR, in the specified
input range of ±5 V.
1.25
1.00
0.75
0.50
0.25
0.00
±6 ±5 ±4 ±3 ±2 ±1 0 1 2 3 4 5 6
Input Voltage (V)
C01
50
25
0
±25
±50
±75
±100
±125
±150
±6 ±5 ±4 ±3 ±2 ±1 0 1 2 3 4 5 6
Input Voltage (V)
C01
Figure 20. Measured DC Transfer Function with ±6-V Input
40
Figure 21. Measured Output Error with ±6-V Input
30
20
10
0
±10
±6 ±5 ±4 ±3 ±2 ±1 0 1 2 3 4 5 6
Input Voltage (V)
C01
Figure 22. Calibrated Output Error with ±6-V Input
16
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