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AD5522 データシート(PDF) 40 Page - Analog Devices |
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AD5522 データシート(HTML) 40 Page - Analog Devices |
40 / 65 page Data Sheet AD5522 Rev. E | Page 39 of 64 Calibration Example Nominal offset coefficient = 32,768 Nominal gain coefficient = 65,535 For example, the gain error = 0.5%, and the offset error = 100 mV. Gain error (0.5%) calibration: 65,535 × 0.995 = 65,207 Therefore, load Code 1111 1110 1011 0111 to the M register. Offset error (100 mV) calibration: LSB size = 10.25/65,535 = 156 µV Offset coefficient for 100 mV offset = 100/0.156 = 641 LSBs Therefore, load Code 0111 1101 0111 1111 to the C register. ADDITIONAL CALIBRATION The techniques described in the Calibration section are usually sufficient to reduce the zero-scale and gain errors. However, there are limitations whereby the errors may not be sufficiently reduced. For example, the offset (C) register can only be used to reduce the offset caused by negative zero-scale error. A positive offset cannot be reduced. Likewise, if the maximum voltage is below the ideal value, that is, a negative gain error, the gain (M) register cannot be used to increase the gain to compensate for the error. These limitations can be overcome by increasing the reference value. SYSTEM LEVEL CALIBRATION There are many ways to calibrate the device on power-on. Following is an example of how to calibrate the FIN DAC of the device without a DUT or DUT board connected. The calibration procedure for the force and measure circuitry is as follows: 1. Calibrate the force voltage (2 points). In FV mode, write zero scale to the FIN DAC. Connect SYS_FORCE to FOHx and SYS_SENSE to MEASVHx, and close the internal force/sense switch (SW7). Using the system PMU, measure the error between the voltage at FOHx/MEASVHx and the desired value. Similarly, load full scale to the FIN DAC and measure the error between the voltage at FOHx/MEASVHx and the desired value. Calculate the M and C values. Load these values to the appropriate M and C registers of the FIN DAC. 2. Calibrate the measure voltage (2 points). Connect SYS_FORCE to FOHx and SYS_SENSE to MEASVHx, and close the internal force/sense switch (SW7). Force voltage on FOHx via SYS_FORCE and measure the voltage at MEASOUTx. The difference is the error between the actual forced voltage and the voltage at MEASOUTx. 3. Calibrate the force current (2 points). In FI mode, write zero scale to the FIN DAC. Connect SYS_FORCE to an external ammeter and to the FOHx pin. Measure the error between the ammeter reading and the MEASOUTx reading. Repeat this step with full scale loaded to the FIN DAC. Calculate the M and C values. 4. Calibrate the measure current (2 points). In FI mode, write zero scale to the FIN DAC. Connect SYS_FORCE to an external ammeter and to the FOHx pin. Measure the error between the ammeter reading and the MEASOUTx reading. Repeat this step with full scale loaded to the FIN DAC. 5. Repeat this procedure for all four channels. Similarly, calibrate the comparator and clamp DACs, and load the appropriate gain and offset registers. Calibrating these DACs requires some successive approximation to find where the comparator trips or the clamps engage. |
同様の部品番号 - AD5522 |
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同様の説明 - AD5522 |
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