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Electric motor control chip and method

  • US 5,581,254 A
  • Filed: 03/30/1994
  • Issued: 12/03/1996
  • Est. Priority Date: 03/30/1994
  • Status: Expired due to Term
First Claim
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1. A circuit for digitizing first and second analog signals for digital processing in a motor control system including a motor and a load driven by the motor, the circuit comprising in combination:

  • (a) first and second conductors conducting the first and second analog signals, respectively;

    (b) an analog-to-digital conversion circuit including a CDAC having a charge summing conductor connected to an input of a bit decision comparator;

    (c) first and second simultaneous sample and hold MSB circuits,the first simultaneous sample and hold MSB circuit includingi. a first MSB switch circuit connected to a third conductor, a first sampling switch connected between the first conductor and the third conductor, and a first MSB capacitor having first and second terminals, the first terminal of the first MSB capacitor being connected to the third conductor,ii. a first isolation switch selectively coupling the second terminal of the first MSB capacitor to the first charge summing conductor during conversion of the first analog signal to a digital number,iii. a first MSB capacitor grounding switch coupling the second terminal of the first MSB capacitor to a reference voltage during simultaneous sampling of the first and second simultaneous sample and hold MSB circuits,the second simultaneous sample and hold MSB circuit includingiv. a second MSB switch circuit connected to a fourth conductor, a second sampling switch connected between the second conductor and the fourth conductor, and a second MSB capacitor having first and second terminals, the first terminal of the second MSB capacitor being connected to the fourth conductor,v. a second isolation switch selectively coupling the second terminal of the second MSB capacitor to the charge summing conductor during conversion of the second analog signal to a digital number, andvi. a second MSB capacitor grounding switch coupling the second terminal of the second MSB capacitor to the reference voltage during simultaneous sampling of the first and second simultaneous sample and hold MSB circuits,whereby the first and second analog signals can be simultaneously sampled and held in the first and second simultaneous sample and hold MSB circuits, respectively, and then sequentially converted to digital numbers by the analog-to-digital conversion circuit.

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