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We want to develop linear magnetic encoder, so for that we are using linear magnetic tape with pole distance of 0.5 mm an length of tape is 55mm so total pole pair would be 55.
by using linear hall sensor, it would give a sine wave with a period of 1 mm , I want to convert this 1 mm sine wave signal into discretize it to 20 positions with smallest electronics possible and at low cost.
Can you tell us the amplitude and frequency of that sinewave output? If the amplitude is very small and/or the signal frequency is very fast, this will change which ADC is appropriate for your application (or at least narrow down the possibilities).
Or, if you have a sensor part number, that will be even better.
and one more thing as the length of magnetic tape is 55 mm , it will give sine wave output over 1 mm.
and ADC will convert this analog signal into digital for 1 mm distance ,to have digital ouput over 55 mm we need ADC with counter so that after 1 mm distance it will add q to each output.
According to the datasheet, the hall sensor output is +/-375 G, with a sensitivity of 4 mV/G and a steady-state output voltage of 1.65 V (assuming VCC = 3.3V).
This gives you an output voltage of +/- 375*0.004 = +/-1.5V, or an input range of 0.15 V to 3.15 V.
I am not sure how fast the tape is moving, which means we do not know how often the ADC needs to sample. But I would imagine the tape is not moving very quickly (at least relative to ADC sampling rates), so something like the ADS7040 (8-bit), ADS7041 (10-bit) or ADS7042 (12-bit) would be good options.
These ADCs are identical other than their resolutions as described above. They can operate on a 3.3 V supply (AVDD & DVDD), they are single-ended input (VIN = 0 V to AVDD), they can sample up to 1 MSPS, and are offered in a 1.5 mm x 1.5 mm QFN package. They are also some of the lowest cost ADCs we have available today. So they meet your requirements of very small and very low cost, while also being able to measure the hall sensor output.
If you choose a fast sample rate, you will need a driver amp for your ADC. For a system solution, you can take a look at this reference design that discusses driver amp selection for different data rates using the ADS7042. You will notice that at the low data rates (10 kSPS), no driver amp is required in the ref design.
Let me know if you have additional questions about these ADC recommendations.
