Output slew rate control in low voltage differential signal (LVDS) driver

A differential signal driver comprising:

• a pre-driver circuit configured to receive a first differential input signal and a second differential input signal, and in response, provide a first output control voltage and a second output control voltage;
• and
• an output driver circuit configured to provide a differential output signal in response to the first and second output control voltages,
• wherein the pre-driver circuit comprises:
• a current source configured to provide a charging current;
• a current sink configured to provide a discharging current;
• a first capacitor;
• a second capacitor;
• a first set of switching transistors configured to selectively couple the first capacitor to either the current source or the current sink in response to the first differential input signal, thereby developing the first output control voltage on the first capacitor;
• a second set of switching transistors configured to selectively couple the second capacitor to either the current source or the current sink in response to the second differential input signal, whereby the second output control voltage is developed on the second capacitor;
• and
• a bias control circuit configured to provide a first set of bias voltages to the current source, thereby causing the current source to provide the charging current, and a second set of bias voltages to the current sink, thereby causing the current sink to provide the discharging current, wherein the bias control circuit includes a reference current generator configured to generate a reference current, current mirror circuitry configured to generate first and second sets of bias voltages in response to the reference current.

A method of operating a differential signal driver comprising:

• generating a constant charging current;
• generating a constant discharging current;
• charging a first capacitor with the constant charging current when a differential input signal has a first state, and discharging the first capacitor with the constant discharging current when the differential input signal has a second state, thereby developing a first output control voltage on the first capacitor;
• charging a second capacitor with the constant charging current when the differential input signal has the second state, and discharging the second capacitor with the constant discharging current when the differential input signal has the first state, thereby developing a second output control voltage on the second capacitor;
• and
• driving a differential output signal in response to the first and second output control voltages.