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Chapter 4
Calibrating the Board
Introduction
Calibrate the board using the InstaCal utility after the board has fully warmed up. The recommended
Calibration theory
The
The analog input circuits are calibrated for both offset and gain (Figure 3).
Offset calibration for the analog input is performed directly on the input amplifier (PGIA) with coarse and fine trim DACs acting on the amplifier.
For input gain calibration, a precision calibration reference is used with coarse and fine trim DACs acting on the ADC.
Analog In
PGIA
Variable Gain
A/D
Trim DAC | ||
Coarse | ||
Offset |
Trim DAC
Fine
Figure 3. Analog input circuit calibration
The analog output circuits are calibrated for both offset and gain (Figure 4). This circuit is duplicated for both DAC0 and DAC1.
Offset adjustments are made in the output buffer section. The tuning range of this adjustment allows for max DAC and output buffer offsets.
Gain calibration is performed via DAC reference adjustments.
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| D/A |
| Analog Out |
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| Ref |
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| Gain |
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| Offset |
Trim DAC | Adjust |
| Trim DAC | Adjust |
Coarse |
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Trim DAC |
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Fine |
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Figure 4. Analog output circuit calibration
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