TOP Coil Quadrature Driver Specifications

Revised 4 April 2007

Warning:  This document is no longer maintained and may contain errors and/or superceded requirements.
Note that the frequencies are generated by the circuit, not externally. The two axies, phi-X and phi-Y are identical.  These specs apply to either axis.  Suffix 'p' means 'peak'. TBD means To Be Determined.  Any TBD values can be calculated if required but only estimated otherwise, to save time.
# Parameter Conditions Value and Notes
1 Expected coil parameters 0 Ohms min, 0.14 Ohms typ, 0.17 Ohms max.  1uH max.
2 Current Per phase, independantly adjustable. 20A peak (14.1A rms). Maybe raise to 25Ap.
3 Current as related to amplitude control word, 0 to 4095 Icoil = 0.2 * 10^((n /4095) where n is amplitude value, Icoil is peak current.
4 Frequency Either preset at anything up to 25KHz (now using 20KHz) or internal switch setting to one of 32 set frequencies.
5 Frequency stability Over time and ambient temperature ±50PPM max
6 Frequency synthesis, amplitude For any output current. 12-bit (increments are 5e-5 of peak)
7 Frequency synthesis, temperal Frequency dependant. 1024 samples per cycle (e.g. every 50nS for 20KHz).
8 Phase shift control word, 0 to 255. Phi-X is reference, phi-Y adjustable 0  to180° in 256 steps of 0.703°.
9 Enable/disable Within 50nS.
10 Offset current when disabled Trimpot adjustable Drift TBD, should be <1mA.
11 Current noise when disabled TBD but estimated as insignificant.
12 Current sensitivity to resistance changes of coils <1e-3
13 Interaction of the two phases With one pahse at 20Ap and the other zero TBD but estimated at <10mA.
Notes to line #:
   6 and 7) Filtering will smooth out the steps anyway.
   7) can double sample rate if required.
   8) Can change to 0° to 180°, or, 0° to 90°.
   9) This is the generated signal delay, current is limited by amplifier and coil response of about 2 cycles to <0.1%.