Systems and method include receiving counter update requests that are at a maximum frequency of f.sub.counters; sending the counter update requests to a main block of counters that operate at a maximum frequency of f.sub.main, where (f.sub.main)≥(f.sub.counters)/2; and responsive to a block of the main block of counters experiencing an overflow, sending corresponding counter update requests for the block of the main block of counters experiencing the overflow to a cache counter block that operates at a maximum frequency of f.sub.cache, where (f.sub.main)≥(f.sub.cache) and (f.sub.cache)≥(f.sub.counters)−(f.sub.main). The counter update requests can be for Y×K total counters, and the main block of counters can include Y blocks of counters each block having K counters, Y and K are positive integers. (f.sub.main)≥(f.sub.counters)/2 ensures only one block of the main block of counters overflows simultaneously.

In an embodiment, a method includes: providing a gray-coded time reference to a time-to-digital converter (TDC); receiving an event from an event signal; latching the gray-coded time reference into a memory upon reception of the event signal; and updating a time-of-flight (ToF) histogram based on the latched gray-coded time reference.

Embodiments of the present invention relate to an architecture that uses hierarchical statistically multiplexed counters to extend counter life by orders of magnitude. Each level includes statistically multiplexed counters. The statistically multiplexed counters includes P base counters and S subcounters, wherein the S subcounters are dynamically concatenated with the P base counters. When a row overflow in a level occurs, counters in a next level above are used to extend counter life. The hierarchical statistically multiplexed counters can be used with an overflow FIFO to further extend counter life.

A frequency divider circuit includes: a first frequency dividing circuit configured to divide a first clock signal to generate a first frequency-divided clock signal; a second frequency dividing circuit configured to divide a second clock signal having the same frequency as the first clock signal and having a first phase difference with respect to the first clock signal to generate a second frequency-divided clock signal; a detection circuit configured to detect a phase relationship between the first frequency-divided clock signal and the second frequency-divided clock signal; and a selection circuit configured to select and output one of the second frequency-divided clock signal and an inverted signal of the second frequency-divided clock signal which are generated by the second frequency dividing circuit, based on the phase relationship between the first frequency-divided clock signal and the second frequency-divided clock signal detected by the detection circuit.

A frequency divider circuit includes: a first frequency dividing circuit configured to divide a first clock signal to generate a first frequency-divided clock signal; a second frequency dividing circuit configured to divide a second clock signal having the same frequency as the first clock signal and having a first phase difference with respect to the first clock signal to generate a second frequency-divided clock signal; a detection circuit configured to detect a phase relationship between the first frequency-divided clock signal and the second frequency-divided clock signal; and a selection circuit configured to select and output one of the second frequency-divided clock signal and an inverted signal of the second frequency-divided clock signal which are generated by the second frequency dividing circuit, based on the phase relationship between the first frequency-divided clock signal and the second frequency-divided clock signal detected by the detection circuit.

A high linearity phase interpolator (PI) is disclosed. A phase value parameter indicative of a desired phase difference between an output signal and an input clock signal edge may be provided by control logic. A first capacitor may be charged for a first period of time with a first current that is proportional to the phase value parameter to produce a first voltage on the capacitor that is proportional to the phase value parameter. The first capacitor may be further charged for a second period of time with a second current that has a constant value to form a voltage ramp offset by the first voltage. A reference voltage may be compared to the voltage ramp during the second period of time. The output signal may be asserted at a time when the voltage ramp equals the reference voltage.

A high linearity phase interpolator (PI) is disclosed. A phase value parameter indicative of a desired phase difference between an output signal and an input clock signal edge may be provided by control logic. A first capacitor may be charged for a first period of time with a first current that is proportional to the phase value parameter to produce a first voltage on the capacitor that is proportional to the phase value parameter. The first capacitor may be further charged for a second period of time with a second current that has a constant value to form a voltage ramp offset by the first voltage. A reference voltage may be compared to the voltage ramp during the second period of time. The output signal may be asserted at a time when the voltage ramp equals the reference voltage.

A frequency divider circuit includes: a first latch circuit that including: a pair of input transistors each having a gate thereof configured to connect to a signal line to which a first voltage is supplied; and a pair of output nodes, and configured to receive a single-phase clock signal; and a second latch circuit of SR-type, the second latch circuit having a set input thereof and a reset input thereof configured to connect to the pair of output nodes of the first latch circuit, and configured to output differential clock signals of which frequency is half a frequency of the single-phase clock signal. The first latch circuit is configured to perform amplification and reset operations alternately repeatedly in response to the single-phase clock signal.

A device includes a clock generator configured to generate a root clock signal based on an input clock signal and a clock generator divider integer setting. The device also includes a first component coupled to the clock generator and configured to generate a first component clock signal based on the root clock signal and a first component divider integer setting. The device also includes a second component coupled to the clock generator and configured to generate a second component clock signal based on the root clock signal and a second component divider integer setting. The device also includes sync circuitry coupled to each of the clock generator, the first component, and the second component, wherein the sync circuitry is configured to perform synchronized adjustments to the root clock signal, the first component clock signal, and the second component clock signal.

A system and method for efficiently generating clock signals are described. In various implementations, an integrated circuit includes multiple clock frequency dividers both at its I/O boundaries and across its die. A clock frequency divider utilizes a first clock divider and a second clock divider that receive input clock signals with an initial phase difference between them. The first clock divider and the second clock divider generate output clock signals that have frequencies that are a fraction of the frequencies of the received input clock signals. The second clock divider uses a combined multiplexer and flip-flop (combined mux-flop) circuit. The combined mux-flop circuit receives a reset signal that is asserted asynchronously with respect to an input clock signal received by the second clock divider. The second clock divider generates an output clock signal that has the initial phase difference with an output clock signal of the first clock divider.