Low-power ethernet transmitter

Abstract

An electrical circuit comprising a line driver for providing Ethernet signals is disclosed. The line driver comprises a voltage mode line driver for producing 1000BT and 100BT Ethernet signals and an active output impedance line driver arranged parallel to the voltage mode line driver. The line driver is capable of producing 1000BT or 100BT or 10BT Ethernet signals, wherein either the voltage mode line driver or the active impedance line driver is active.

What is claimed is: 
     
         1 . A line driver, comprising:
 a multiplexer, having first and second output ports, configured to multiplex an analog signal to provide a first signal or a second signal in response to a negotiated transmission speed;   a first line driver, coupled to the first output port, configured to produce a first Ethernet signal, having a first speed, in response to the first signal; and   a second line driver, coupled to the second output port, configured to produce a second Ethernet signal, having a second speed, in response to the second signal.   
     
     
         2 . The line driver of  claim 1 , wherein the first line driver comprises a voltage mode line driver, and
 wherein the second line driver comprises an active output impedance line driver.   
     
     
         3 . The line driver of  claim 2 , wherein an output stage of the voltage mode line driver is coupled to a calibration voltage that is configured to calibrate a common mode voltage of the voltage mode line driver, and
 wherein the output of the voltage mode line driver and a supply voltage are fed into a calibration circuit configured to produce the calibration voltage that is approximately half of the supply voltage.   
     
     
         4 . The line driver of  claim 2 , wherein the voltage mode line driver comprises a first single-pole low-pass filter in a feedback path of the voltage mode line driver, and
 wherein the active output impedance line driver comprises an operational amplifier having a second single-pole low-pass filter in a feedback path of the operational amplifier.   
     
     
         5 . The line driver of  claim 4 , wherein the first single-pole low-pass filter comprises an adjustable capacitor that is configured to adjust a frequency of the first single-pole low-pass filter, and
 wherein a frequency of the second single-pole low-pass filter is at a frequency of approximately 80 MHz.   
     
     
         6 . The line driver of  claim 1 , wherein the first Ethernet signal comprises a 100BT or a 1000BT Ethernet signal, and
 wherein the second Ethernet signal comprises a 10BT Ethernet signal.   
     
     
         7 . The line driver of  claim 1 , wherein the second line driver is further configured to be inactive when the first line driver is configured to produce the first Ethernet signal, and
 wherein the first line driver is further configured to be inactive when the second line driver is configured to produce the second Ethernet signal.   
     
     
         8 . The line driver of  claim 1 , wherein the first line driver is further configured to receive the first signal being clocked by a first clock signal corresponding to 100BT or 1000BT wired Ethernet signals, and
 wherein the second line driver is further configured to receive the second signal being clocked by a second clock signal corresponding to a 10BT wired Ethernet signal.   
     
     
         9 . The line driver of  claim 1 , further comprising:
 a connection pad configured to output the first or the second Ethernet signals to a transmission line,   wherein the first line driver is further configured to exhibit a first impedance to the transmission line that is larger than a characteristic impedance of the transmission line when the first line driver is configured to be inactive, and   wherein the second line driver is further configured to exhibit a second impedance to the transmission line that is larger than the characteristic impedance when the second line driver is configured to be inactive.   
     
     
         10 . A method for producing Ethernet signals, comprising:
 multiplexing an analog signal by a line driver to provide a first signal or a second signal in response to a negotiated transmission speed; and   producing, by the line driver, a first Ethernet signal, having a first speed, in response to the first signal or a second Ethernet signal, having a second speed, in response to the second signal.   
     
     
         11 . The method of  claim 10 , further comprising:
 converting a plurality of digital symbols to the analog signal.   
     
     
         12 . The method of  claim 11 , wherein the second signal comprises a current-mode signal, and
 wherein producing comprises:
 converting the second signal from a current-mode signal to a voltage mode signal; and 
 producing the second Ethernet signal in response to the voltage mode signal. 
   
     
     
         13 . The method of  claim 10 , wherein producing comprises:
 introducing an intermediate step in a rising edge and a falling edge of the analog signal when the negotiated transmission speed comprises a 100BT mode.   
     
     
         14 . The method of  claim 10 , wherein the first speed corresponds to a 10BT mode, and
 wherein the second speed corresponds to a 100BT mode or a 1000BT mode,   further comprising:
 setting the negotiated transmission speed to the 10BT mode to produce the second Ethernet signal upon power up of the line driver; 
 changing the negotiated transmission speed to the 100BT mode or the 1000BT mode during an ongoing transmission; 
 ceasing production of the second Ethernet signal in response to the changing; and 
 commencing production of the first Ethernet signal in response to the changing. 
   
     
     
         15 . The method of  claim 10 , further comprising:
 filtering the first signal using a first single-pole low-pass filter of adjustable frequency in the line driver, and   filtering the second signal using a second single-pole low-pass filter in the line driver.   
     
     
         16 . An integrated circuit, comprising:
 a digital-to-analog converter (DAC) configured to output an analog signal;   a multiplexer configured to multiplex the analog signal to provide a first signal or a second signal in response to a negotiated transmission speed;   a first line driver, coupled to the multiplexer, configured to produce a first Ethernet signal, having a first speed, in response to the first signal, the first line driver comprising a first feedback path; and   a second line driver, coupled to the multiplexer, configured to produce a second Ethernet signal, having a second speed, in response to the second signal, the second line driver comprising a second feedback path;   wherein the first and the second feedback paths comprise a first and a second single-pole low-pass filter, respectively.   
     
     
         17 . The integrated circuit of  claim 16 , wherein the DAC comprises a multi-level DAC. 
     
     
         18 . The integrated circuit of  claim 16 , wherein the second line driver is further configured to be inactive when the first line driver is configured to produce the first Ethernet signal, and
 wherein the first line driver is further configured to inactive when the second line driver is configured to produce the second Ethernet signal.   
     
     
         19 . The integrated circuit of  claim 18 , further comprising:
 a connection pad configured to output the first or the second Ethernet signals to a transmission line;   wherein the first line driver is further configured to exhibit a first impedance to the transmission line that is larger than a characteristic impedance of the transmission line when the first line driver is configured to be inactive, and   wherein the second line driver is further configured to exhibit a second impedance to the transmission line that is larger than the characteristic impedance of the transmission line when the second line driver is configured to be inactive.   
     
     
         20 . The integrated circuit of  claim 16 , wherein the first line driver is further configured to receive the first signal clocked by a first clock signal corresponding to 100BT or 1000BT Ethernet signals, and
 wherein the second line driver is further configured to receive the second signal clocked by a second clock signal corresponding to a 10BT Ethernet signal.