Abstract:
Certain aspects of the present disclosure generally relate to a driver circuit for a serializer/deserializer (SerDes) transmitter and techniques for operating such a driver circuit. One example driver circuit generally includes a pre-driver circuit, an output stage circuit, and a common-gate buffer circuit coupled between an output of the pre-driver circuit and a first input of the output stage circuit.
Abstract:
Systems and methods for adjusting a phase step size of a clock data recover (CDR) circuit are described according to aspects of the present disclosure. In certain aspects, a method for adjusting a phase step size of a CDR circuit includes sensing a frequency offset of the CDR circuit, and adjusting the phase step size of the CDR circuit based on the sensed frequency offset. The frequency offset may be sensed by sensing a signal level on an integration path of a loop filter of the CDR circuit. The phase step size of the CDR circuit may be adjusted by switching the CDR circuit between a first phase step size and a second phase step size using a modulator (e.g., a sigma-delta modulator).
Abstract:
In one embodiment, a method for generating a reference comprises generating a current that is approximately temperature independent over a temperature range based on an emitter-base voltage of a first bipolar junction transistor (BJT), and generating a first proportional to absolute temperature (PTAT) current based on the emitter-base voltage of the first BJT.
Abstract:
Techniques for reducing noise and power consumption in a loop filter for a phase-locked loop (PLL) are described herein. In one embodiment, a loop filter for a PLL comprises a first proportional capacitor, a second proportional capacitor, an active device, and a plurality of switches. The plurality of switches are configured to alternately couple the first proportional capacitor and the second proportional capacitor to a first charge pump, to alternately couple noise from the active device to the first proportional capacitor and the second proportional capacitor, and to alternately couple the first proportional capacitor and the second proportional capacitor into a feedback circuit, wherein the feedback circuit produces an output voltage of the loop filter.
Abstract:
A voltage controlled oscillator (VCO), including: at least one second upper voltage rail; at least one second lower voltage rail; a ring of N cascaded inverters, wherein the set of N cascaded inverters are coupled between the at least one second upper voltage rail and the at least one second lower voltage rail; at least one first frequency band select circuit coupled between first upper voltage rail and the at least one second upper voltage rail; at least one second frequency band select circuit coupled between the at least one second lower voltage rail and first lower voltage rail; at least one first VCO frequency control circuit coupled between the first upper voltage rail and the at least one second upper voltage rail; and at least one second VCO frequency control circuit coupled between the at least one second lower voltage rail and the first lower voltage rail.
Abstract:
A push-pull driver is provided with a differential amplifier that amplifies a difference between an input voltage and an output voltage to drive a bias node coupled to a diode-connected bias transistor. The push-pull driver is configured to control the drain-to-source voltage for a source-follower output transistor having its gate tied to a gate for the diode-connected bias transistor to be proportional to the drain-to-source voltage for the diode-connected bias transistor. This proportionality prevents excessive static current variation that would otherwise be present in the source-follower output transistor.
Abstract:
A single-ended comparator is disclosed herein. The comparator may be implemented with low-voltage semiconductor devices that are capable of operating with high-voltage signals at an input. The single-ended comparator may be integrated in a larger circuit to receive and detect information provided on the input at voltage levels higher than the levels supported by the rest of the circuit, and transfer the information in the received signal for use by the rest of the circuit.
Abstract:
Techniques for reducing noise and power consumption in a loop filter for a phase-locked loop (PLL) are described herein. In one embodiment, a loop filter for a PLL comprises a first proportional capacitor, a second proportional capacitor, an active device, and a plurality of switches. The plurality of switches are configured to alternately couple the first proportional capacitor and the second proportional capacitor to a first charge pump, to alternately couple noise from the active device to the first proportional capacitor and the second proportional capacitor, and to alternately couple the first proportional capacitor and the second proportional capacitor into a feedback circuit, wherein the feedback circuit produces an output voltage of the loop filter.
Abstract:
An equalizing circuit includes a first current summer that receives a data signal and a first plurality of feedback signals, a first multiplexer that selects a first sampling clock signal from a plurality of clock signals using a signal that indicates a mode of operation of the equalizing circuit, and a first slicer that samples the output of the first current summer in accordance with timing provided by the first sampling clock signal. The equalizing circuit can have a second current summer that receives the data signal and a second plurality of feedback signals, a second multiplexer that selects a second sampling clock signal from the plurality of clock signals using the signal that indicates the mode of operation of the equalizing circuit, and a second slicer that samples the output of the second current summer according to timing provided by the second sampling clock signal.
Abstract:
A data transmitter includes: a plurality of parallel driver slices, a first slice of the plurality of parallel driver slices having a first signal generator circuit with a first transistor coupled to a data signal and in series with a second transistor coupled to a first bias signal; and a first bias circuit including a third transistor and a fourth transistor in series with a first current source, the first bias circuit further including a first operational amplifier (op amp) having a first input coupled to a first reference voltage and a second input coupled between the fourth transistor and the first current source, an output of the first op amp configured to provide the first bias signal to the second transistor and to the third transistor.