We have selected AD7609 for a high precision output conversion as it is an 18-bit ADC.
Using Eval-AD7609EDZ, we are getting only 12-bit precision when Interfaced in serial with a TMS320F28335 using Serial Peripheral Interface(SPI). We cannot go for Over-Sampling, because OS adds delay in Processing and our system is time constraint.
- We have connected TMS320F28335 and ADC using a bus connector with a length of about 5cm. (Image is attached)
- SPI frequency set to 6MHz.
- Range of ADC used is +/- 10V.
- Vdrive = 3.3V and Vcc = 5V, both supplied from SMPS
- Analog Input to Channel 1 from a 24V Battery and all other channels(2-8) connected to GND.
- DB7 pin is used for data capturing of 8-channels by providing 144 Clocks and DB8 pin is left pen.
- DB0-DB6 and DB9-DB17 are connected to GND.
Also tested in parallel Interface with TMS320F28335 and the results are 12-bit only precision same as Serial Interface.
Please answer these questions and help me improve my AD7609 Outputs with a better precision & accurate output:
- Can AD7609 provide more precision output than 12-bit? If yes, What is the maximum precision of AD7609 we can expect?
- Is there any additional care to be taken other than the information provided in data sheet for traces.
- How to take Differential Non-Linearity = -0.99/+2 LSB's,
Integral Non-Linearity = +/-7.5 LSB's
Total Unadjusted Error = +/- 10 LSB's into consideration for ADC results as described in Page 4 of AD7609 Data-sheet
Please reply as soon as possible.