Method and apparatus for generating a phase dependent control signal

Claim 1

A packetized dynamic random access memory, comprising: at least one array of memory cells adapted to store data at a location determined by a row address and a column address responsive to a command word; a row address circuit adapted to receive and decode the row address, and select a row of memory cells corresponding to the row address responsive to the command word; a column address circuit adapted to receive or apply data to one of the memory cells in the selected row corresponding to the column address responsive to the command word; a data path circuit adapted to couple data between an external terminal and the column address circuit responsive to the command word; and a command data latch circuit for storing a command data packet at a time determined from a command clock signal, the command data latch comprising: a latch circuit having a data input and a clock input, the data input being adapted to receive the command data packet and store the command data packet responsive to a clock signal applied to the clock input; and a clock generator circuit for generating the clock signal from a master clock signal, the clock generator circuit comprising: a first delay-lock loop having a first voltage controlled delay circuit receiving a reference clock signal and generating a sequence of clock signals which are increasingly delayed from the reference clock signal to a last clock signal by delaying the reference clock signal by respective delays that are a function of a first control signal, and a first phase detector comparing the phase of the first and second clock signals in the sequence and generating the first control signal as a function of the phase difference therebetween, the first phase detector comprising: a first phase detector circuit having first and second input terminals coupled to receive the first and second clock signals, respectively, and an output terminal, the first phase detector circuit producing a first select signal having a duty cycle according to the phase relationship between a first edge of the first and second clock signals in the sequence; a second phase detector circuit having first and second input terminals coupled to receive the first and second clock signals, respectively, and an output terminal, the second phase detector circuit producing a second select signal having a duty cycle according to the phase relationship between a second edge of the first and second clock signals in the sequence; a first charge pump having first and second input terminals coupled to the output terminals of the first and second phase detector circuits and an output terminal, the first charge pump producing a non-varying control signal responsive to a first combination of logic levels of the first and second select signals, an increasing control signal responsive to a second combination of logic levels of the first and second select signals, and a decreasing control signal responsive to a third combination of logic levels of the first and second select signals; and a capacitor coupled to the output terminal of the first charge pump; a second delay-lock loop having a second voltage controlled delay circuit receiving a master clock signal and generating a reference clock signal having delay relative to the master clock signal that is a function of a second control signal, and a second phase detector comparing the phase of the master clock signal to the phase of a selected one of the clock signals in the sequence and generating the second control signal as a function of the difference therebetween, the second phase detector comprising: a third phase detector circuit having first and second input terminals coupled to receive the master clock signal and the selected one of the clock signals in the sequence, respectively, and an output terminal, the third phase detector circuit producing a first select signal having a duty cycle according to the phase relationship between a first edge of the master clock signal and the selected one of the clock signals in the sequence; a fourth phase detector circuit having first and second input terminals coupled to receive the master clock signal and the selected one of the clock signals in the sequence, respectively, and an output terminal, the fourth phase detector circuit producing a second select signal having a duty cycle according to the phase relationship between a second edge of the master clock signal and the selected one of the clock signals in the sequence; an a second charge pump having first and second input terminals coupled to the output terminals of the third and fourth phase detector circuits and an output terminal, the second charge pump producing a non-varying control signal responsive to a first combination of logic levels of the first and second select signals, an increasing control signal responsive to a second combination of logic levels of the first and second select signals, and a decreasing control signal responsive to a third combination of logic levels of the first and second select signals; and a capacitor coupled to the output terminal of the second charge pump; a multiplexer coupled to the first delay-lock loop to receive the clock signals in the sequence and to couple one of the clock signals in the sequence to the clock input of the latch circuit, the clock signal coupled to the latch circuit being selected by the multiplexer as a function of a select signal applied to a control input of the multiplexer; and a select circuit determining which of the clock signals from the first delay-lock loop should be used to cause the latch circuit to store the command data packet and generating the select signal corresponding thereto.