Patent ID: 7538505

Claim:
A motor circuit for use with a monolithic brushless DC motor having a Hall effect device circuit coupled to said monolithic brushless DC motor, said Hall effect device circuit providing signals indicative of the rotational position and speed of said motor, said motor circuit comprising: a sampling circuit comprising one or more input nodes coupled to said Hall effect device circuit, a sample control input node, and an output node; a motor drive PWM circuit, said PWM circuit having a first output node and having second output nodes coupleable to said motor, said PWM circuit providing a first PWM signal at said first output node and second PWM signals at said second output nodes, said first PWM signal preceding said second PWM signals by a predetermined first time period; an edge detector circuit having an input node coupleable to said PWM circuit first output node to receive said first PWM signal, said edge detector circuit having an output node, said edge detector providing an edge indicating signal at said output node whenever said first PWM signal transitions between two states; a pulse generating circuit having an input node coupled to said edge detector circuit output node, said pulse generating circuit having an output node, said pulse generating circuit responsive to each said edge indicating signal to provide a pulse signal at said output node, said pulse signal having a predetermined time duration, said predetermined time duration being selected to be greater than said predetermined first time period and the time period of noise spikes generated by said second PWM signals, said output node of said pulse generating circuit coupled to said sampling circuit sample control input node; and said sampling circuit providing an output signal at said output node having a level that follows the signal level at said sampling circuit input node, said sampling circuit holding the signal level at said output node during said time duration that said pulse signal is present at said sample control input node.