Texas Instruments Corporation

Jagdish Chand Goyal

Srikanth Manian

Sumantra Seth

Krishnaswamy Thiagarajan

Peeyoosh Nitin Mirajkar

Jayawardan Janardhanan

Biman Chattopadhyay

Srinivas Theertham

Debapriya Sahu

Yogesh Darwhekar

Sujoy Chakravarty

Robert Karl Butler

Peter Brendan Considine

Shankaranarayana Karantha

Uttam Kumar Patro

Bharathi Rahuldev Holla

Olivier Depuits

Ashwin Ravisankar

Theertham Srinivas

Sankaran Aniruddhan

A dual-PFD circuit with delay feedback generated by a dual-modulus prescaler based on mode control from a feedback delay generation circuit. The PFD circuit can be used with a PLL feedback divider to divide a VCO clock signal VCO_clk and generate FB and FB_DLY signals. The PLL feedback divider includes a dual modulus prescaler to selectively divide the VCO_clk by either M or M+1 (such as 4/5) based on a divide mode control input to generate a prescaled divide signal, and a programmed counter/divider (N counter/1/N divider) to selectively divide the prescaled divide signal to generate the FB signal, and a delay generation circuit to selectively delay the FB signal by a pre-defined delay to generate the FB_DLY signal. The prescaler is responsive to the pre-defined delay from the delay generation circuit to change divide modes. The dual PFD circuit response to the FB and FB_DLY signals in relation to a reference signal to generate a phase comparison signal. the dual-PFD circuit can be used with a charge-pump coupled to the dual PFD circuit, and responsive the phase comparison signal to generate a frequency tuning voltage, for input to a VCO for generating the VCO clock signal. The dual PFD circuit, charge pump and VCO can be used in a PLL frequency synthesizer.

Dual-PFD feedback delay generation circuit

Frequency synthesis is based on phase synchronizing PLL output across REFERENCE and VCO clock domains (including outputs for multiple PLLs), based on an input (REF-Domain) SYNC signal (phase timing reference). A frequency synthesizer includes a VCO to generate VCO_clk and a PLL output circuit, such as a channel divider, to generate PLL_OUT based on VCO_clk (in the VCO-Domain). The VCO loop includes a PD to phase compare an input PD_clock based on REF_CLK, and a VCO feedback signal based on divided VCO_clk (NDIV_out). SYNC alignment circuitry generates a SYNC alignment signal based on SYNC, PD_clk, and NDIV_out (REF-Domain), which is used to synchronize the PLL output circuit and PLL_OUT to SYNC. If a reference divider generates PD_clk, the SYNC alignment circuitry generates a reset to SYNC-align the reference divider. If the VCO loop uses fractional divide, the SYNC alignment circuitry resets the fractional modulator to a known sequence.

Phase syncronizing PLL output across reference and VCO clock domains

The disclosure provides a frequency synthesizer. It includes a PFD that generates an up signal and a down signal in response to a reference signal and a feedback signal. A charge pump generates a control voltage in response to the up signal and the down signal. A low pass filter generates a filtered voltage in response to the control voltage. An oscillator circuit generates an output signal in response to the filtered voltage. A feedback divider is coupled between the oscillator circuit and the PFD, and divides the output signal by a first integer divider to generate the feedback signal. A sigma delta modulator (SDM) generates a second integer divider in response to the feedback signal, the reference signal, the output signal and the first integer divider. A digital filter is coupled between the SDM and the feedback divider, and filters quantization noise associated with the SDM.

Phase noise improvement techniques for wideband fractional-N synthesizers

A phase lock loop (PLL) includes a voltage-controlled oscillator (VCO) and a frequency detector to generate a FAST signal responsive to a frequency of a reference signal being greater than the frequency of a feedback signal derived from the VCO and to generate a SLOW signal responsive to the frequency of the reference signal being smaller than the frequency of the feedback signal. The PLL also includes a digital charge pump, a loop filter, and a state machine circuit. Responsive to receipt of multiple consecutive FAST signals when the digital charge pump is providing a charging current to the loop filter, the state machine circuit reconfigures the digital charge pump to increase the charging current to the loop filter. Responsive to receipt of multiple consecutive SLOW signals when the loop filter is discharging, the state machine circuit reconfigures the digital charge pump to cause the loop filter's discharge current to increase. Upon detection of a terminal condition, the state machine circuit may disable the digital charge pump and enable operation of an analog charge pump.

Phase lock loop with a digital charge pump

A frequency synthesizer that includes a reference frequency scaler and a phase locked loop (PLL) coupled to the reference frequency scaler. The reference frequency scaler is configured to generate a first reference frequency and a second reference frequency. The PLL is configured to generate a first output frequency based on the first reference frequency during a first timeslot and a second output frequency based on the second reference frequency during a second timeslot. The PLL comprises a loop filter that includes a first switch connected in series to a first capacitor and configured to close during the first timeslot and a second switch connected in series to a second capacitor and configured to open during the first timeslot.

Frequency synthesizer for achieving fast re-lock between alternate frequencies in low bandwidth PLLs

A fractional-N frequency synthesizer that suppresses integer boundary spurs. A frequency synthesizer includes a fractional-N phase locked loop (PLL) and a reference frequency scaler. The reference frequency scaler is coupled to a reference clock input of the PLL, the reference frequency scaler includes a programmable frequency divider, and a programmable frequency multiplier connected in series with the programmable frequency divider. Each of the divider and multiplier is configured to scale a reference frequency provided to the PLL by a programmable integer value.

Fractional-N synthesizer with pre-multiplication

Described examples include circuitry and methods to control lock time of a phase lock loop (PLL) or other locking circuit, in which a phase frequency detector (PFD) circuit is switched from a first mode to provide a control input signal to a charge pump as a pulse signal having a pulse width corresponding to a phase difference between a reference clock signal and a feedback clock signal to a second mode to hold the control input signal at a constant value for a predetermined time in response to detected cycle slip conditions to enhance loop filter current during frequency transitions to reduce lock time for the locking circuit.

Phase frequency detector (PFD) circuit with improved lock time

A clock and data recovery module (CDR) is configured to perform fast locking using only two samples per each unit interval (UI). Two clock phase signals are selected from a plurality of clock phase signals. A sequence of data bits is sampled at a rate of two times per UI responsive to the two clock phase signals in which a first sample of each UI is designated as an edge sample a second sample is designated as a data sample. Each edge sample is voted as early/late as compared to an associated data transition of the sequence of data bits by comparing each edge sample to a next data sample. The sample clocks are locked such that edge samples occur in proximity to data transitions by iteratively adjusting a phase of the two selected clock phase signals by a variable step size in response to the early/late vote.

Fast locking clock and data recovery using only two samples per period

A circuit for use with PWM signal having first pulse and a second pulse, wherein the first pulse has a period and a first duty cycle, and the second pulse has the period and a second duty cycle. The period has clock information therein, the first duty cycle has first data information therein, and the second duty cycle has second data information therein. The circuit includes a first integrating component and a second integrating component. The first integrating component can generate a first voltage corresponding to the first duty cycle and a second voltage corresponding to the first duty cycle. The second integrating component can generate a third voltage corresponding to the second duty cycle and a fourth voltage corresponding to the second duty cycle.

System and method for pulse width modulation

A device includes a sense circuit configured to detect a leakage current from a driver output pad. A current mirror responds to the sense circuit and compensates for the leakage current detected at the driver output pad. A scaled compensation circuit can supply compensation current to the current mirror.

Driver output pad leakage current compensation

In at least some embodiments, an electronic device includes a first data endpoint and differential data transceiver coupled to the first data endpoint. The differential transceiver provides a communication interface between the first data endpoint and a second data endpoint. The differential transceiver compensates for variations in a series impedance and/or a parallel impedance for a differential data line between the differential transceiver and the second data endpoint.

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Bengaluru, India

Jagdish Chand Goyal