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选择合适的系列电压基准源的绝对精度电压输出

作者： 时间：2012-01-30 来源：网络 收藏
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0°C to 70°C (commercial)
-40°C to 85°C (extended)
15°C to 45°C ( commercial)
Signal BW
10Hz to 10kHz
DC to 1kHz
DC to 10Hz
DC to 10Hz
DAC Calibration
None
Annual (gain and offset)
One-time factory (gain and offset)
None
Max Error Target
15625ppm (16LSB @ 10 bits)
122ppm (2LSB @ 14 bits)
977ppm (4LSB @ 12 bits)
3906ppm (16LSB @ 12 bits)

Each example is analyzed, focusing on the specifications that apply to that particular design. The results of this analysis, along with the results of the previous section, are summarized in an error budget in Table 5.

It is most convenient to do the error-budget accounting in ppm, although this could be done equivalently in other units such as %, mV, or LSBs. It's important to apply the proper scaling and to use the proper normalization factor to get the correct error values. Reference error terms can be equivalently calculated relative to the reference voltage or the DAC output voltage. For example, if we assume a reference error of 2.5mV (noise, drift, etc.) and a reference voltage of 2.5V, we get the following:
Reference Output Error = 106 × 2.5mV / 2.5V = 1000ppm
If we assume that the DAC output amplifier has a gain of 2.0, both the error and the reference voltage are scaled, so we get the same result at the DAC output (5V full-scale range):
DAC Output Error = 106 × (2.5mV × 2) / (2.5V × 2) = 1000ppm
Table 5. Error-Budget Analysis
Parameter
Design A
Design B
Design C
Design D
Main Design Objectives
Low cost, loose accuracy
High absolute accuracy and precision
One-time calibrated, low drift
Low voltage, battery powered, moderate accuracy
Example Application
Consumer audio device
Lab instrument
Digital offset and gain adjustment
Portable instrument
Reference Initial Error
4000ppm
-
-
1600ppm
Reference/DAC Post- Calibration Error
-
0ppm
244ppm
-
Reference Tempco Error