QUESTION: I noticed that Table 9 in the datasheet of ad2s1210 described the resolution. It mentioned that when in 12bit, the velocity LSB is 0.488rps. It seems that this value is also associated with CLKIN.
I want to know that if the full scale of velocity is 500rps, LSB = 500/(2^11-1)=0.061rps. How to calculate velocity LSB in different full scales? Does it need to consider CLKIN value?
ANSWER:
Take note that the values of RPS also depend on the CLKIN. The computations below were referred to 8.192 MHz CLKIN. If CLKIN is changed to a different value, let's say 10.124 MHz, the maximum tracking rate will also change. The new max tracking rate is +/- 3125 rps. If the max tracking rate is a concern, then CLKIN should be considered.
- Calculating the Velocity LSB (rps): RPS_FS/ (2^n).
- For example, if your resolution (N) is 10 bits, you will have an RPS of +/- 2500 rps. For its full scale, you will be having 5000 rps.
- Solving for its Velocity LSB (rps): 5000 / (2^10) = 4.88 rps
- Solving for its Velocity LSB (rps): 5000 / (2^10) = 4.88 rps
- On the other hand, if your resolution is 16-bits. You will have an RPS of +/- 125 rps. Its full scale will be 250 rps.
- Solving for its Velocity LSB (rps): 250 / (2^16) = 0.004 rps
- Solving for its Velocity LSB (rps): 250 / (2^16) = 0.004 rps
- For example, if your resolution (N) is 10 bits, you will have an RPS of +/- 2500 rps. For its full scale, you will be having 5000 rps.
- So, if your FS is 500, then computation will be 500/(2^N).