Low voltage differential signaling [LVDS] driver with pre-emphasis
View Patent ↗A Low Voltage Differential Signaling Driver with Pre-emphasis and including a primary stage having a first switching circuit providing an output representing a sequence of pulses at a predetermined current level, a secondary stage having a second switching circuit arranged to provide an additional current level for the pulses, and a control circuit arranged to provide control signals for controlling the first and second switching circuits. The control circuit detects a difference in level between two consecutive pulses of the sequence and provides accordingly control signals to the first and second switching circuits. The control signals are such that when two consecutive pulses of the sequence are different, the additional current level is added to the predetermined current level, whilst when two consecutive pulses of the sequence are identical, the additional current level is subtracted from the predetermined current level.
1. A Low Voltage Differential Signaling [LVDS] Driver for providing a driver output representing a sequence of data bits, said driver comprising:
a primary stage having first switching component arranged to provide a first output current in response to first control signals,
a secondary stage having second switching component arranged to provide a second output current in response to second control signals,
a control circuit arranged to provide said first and second control signals for controlling said first and second switching components,
characterized in that said control circuit is arranged to detect a difference in level between two consecutive bits of said sequence and to provide said first and second control signals in such a way that:
when said two consecutive bits of said sequence are different, said first and second output currents are added to generate said driver output; whilst
when said two consecutive bits of said sequence are identical, said second current is subtracted from said first current to generate said driver output.
2. The Low Voltage Differential Signaling Driver according to claim 1 , wherein
said primary stage also comprises a first current source and a second current source and a first current sink and a second current sink, and
said secondary stage also comprises a current source and a current sink.
3. The Low Voltage Differential Signaling Driver according to claim 2 , wherein
said Driver further comprises at least one current control circuit,
said second current source and said second current sink of said primary stage are substantially identical to said current source and said current sink of said secondary stage, and
said second current source and said second current sink of said primary stage and said current source and said current sink of said secondary stage are controlled by said current control circuit.
4. The Low Voltage Differential Signaling Driver according to claim 3 , wherein said Driver comprises N current control circuits with N>2, adapted to be combined in order to control said first and second current sources and said first and second current sinks of said primary stage.
5. The Low Voltage Differential Signaling Driver according to claim 1 , wherein said control circuit comprises four standard flip-flop cells.
6. The Low Voltage Differential Signaling Driver according to claim 1 , wherein said Driver further comprises a common-mode bias circuit including a first resistor pair, a second resistor pair and an Operational Transconductance Amplifier.
7. The Low Voltage Differential Signaling Driver according to claim 6 , wherein
said first resistor pair is coupled to a first input of said Operational Transconductance Amplifier,
said Amplifier is coupled to said second resistor pair, and
a reference voltage is applied to a second input of said Amplifier.