Patent ID: 7570568

Claim:
A writing current circuit ( 42 ) adapted for supplying a controlled electrical current to a laser diode ( 34 ) included in a drive ( 10 ), the drive ( 10 ) being adapted for swiftly recording digital data onto a Digital Video Disc (“DVD”) ( 16 ), the writing current circuit ( 42 ) receiving from a control processor ( 14 ) included in the drive ( 10 ) both: a. write control digital data via a writing control bus ( 44 ) which interconnects the writing current circuit ( 42 ) and the control processor ( 14 ); and b. serial digital data to be recorded on a DVD ( 16 ) via a recorded data bus ( 46 ) which also interconnects the writing current circuit ( 42 ) and the control processor ( 14 ), the writing current circuit ( 42 ) comprising: a plurality of thermometer code registers ( 52 ) each of which is adapted for storing a numerical value which specifies a particular quantity of electrical current which the writing current circuit ( 42 ) may supply to the laser diode ( 34 ), the thermometer code registers ( 52 ) respectively receiving the stored numerical values from the control processor ( 14 ) via the writing control bus ( 44 ); a current control register ( 58 ) which is adapted for receiving a numerical value from a selected one of the thermometer code registers ( 52 ) via a thermometer code transfer bus ( 56 ) which interconnects the current control register ( 58 ) with all of the thermometer code registers ( 52 ), serial digital data received by the thermometer code registers ( 52 ) via the recorded data bus ( 46 ) specifying a sequence in which individual thermometer code registers ( 52 ) supply respective numerical values to the current control register ( 58 ) via the thermometer code transfer bus ( 56 ) whereby the writing current circuit ( 42 ) supplies a particular electrical current waveform to the laser diode ( 34 ); and a plurality of separate current sources ( 62 ) each of which receives a single output signal from the current control register ( 58 ), the output signal respectively received by each current source ( 62 ) from the current control register ( 58 ): a. when in a first state activating the receiving current source ( 62 ) for supplying a particular quantity of electrical current to the laser diode ( 34 ); and b. when in a second state deactivating the receiving current source ( 62 ) for supplying the particular quantity of electrical current to the laser diode ( 34 ).