Delay locked loop circuit and signal delay method
A multiplier PLL multiplies a reference clock and outputs the multiplied clock. A DLL compares the clock output from the multiplier PLL with a clock obtained by delaying the clock output from the multiplier PLL. The DLL generates a delay signal having a given amount of delay based on the comparison result. A delay control signal operation circuit generates a delay control signal based on the delay signal generated by the DLL. A first delay circuit delays an input signal based on the delay control signal generated by the delay control signal operation circuit.
1 . A delay locked loop circuit comprising:
a multiplier PLL (Phase Lock Loop) that multiplies a reference clock and outputs the multiplied reference clock;
a DLL (Delay Locked Loop) that applies an amount of delay corresponding to a given cycle to the clock output from the multiplier PLL to generate a delay signal having a given amount of delay so that the delay signal has the same phase as the clock output from the multiplier PLL;
a delay control signal operation circuit that generates a delay control signal having a given amount of delay based on the delay signal having the given amount of delay; and
a first delay circuit that delays an input signal based on the delay control signal.
2 . The delay locked loop circuit according to claim 1 , wherein
the DLL includes a second delay circuit that applies a delay corresponding to a given cycle to the clock output by the multiplier PLL, and
the first and second delay circuits include one or more delay elements having substantially the same configuration.
3 . The delay locked loop circuit according to claim 1 , wherein
the DLL includes a phase comparison circuit that compares a phase of the clock output from the multiplier PLL with a phase of a delayed clock output from the multiplier PLL; and a delay control circuit that generates a delay signal based on a comparison result of the phase comparison circuit.
4 . The delay locked loop circuit according to claim 2 , wherein
the first delay circuit includes a circuit that is substantially the same as the second delay circuit, and
the delay control signal operation circuit controls the first delay circuit and the second delay circuit by supplying the delay control signal to the first delay circuit and the DLL.
5 . The delay locked loop circuit according to claim 1 , further comprising:
a first selection part that selects one of the clock output from the multiplier PLL and the reference clock based on a selection signal, and outputs a selected clock to the DLL; and
a second selection part that selects one of the delay signal and the delay control signal based on the selection signal, and outputs a selected signal to the first delay circuit,
wherein the DLL generates the delay signal by applying an amount of delay corresponding to the given cycle to the signal output from the first selection part so that the delay signal has the same phase as the signal output from the first selection part, and
the first delay circuit delays an input signal based on the signal output from the second selection part.
6 . The delay locked loop circuit according to claim 5 , further comprising:
a selection signal generation circuit that compares an amount of delay of the clock by the DLL with an amount of delay corresponding to a clock cycle of the reference clock, and generates the selection signal for the first selection part to select the clock output from the multiplier PLL and for the second selection part to select the delay control signal when the amount of delay of the clock by the DLL is smaller than an amount of delay corresponding to a clock cycle of the reference clock, and generates the selection signal for the first selection part to select the reference clock and for the second selection part to select the delay signal when the amount of delay of the clock by the DLL is larger than the amount of delay corresponding to a clock cycle of the reference clock.
7 . An LSI device comprising the delay locked loop circuit according to claim 1 .
8 . A signal delay method comprising:
multiplying a reference clock by a multiplier PLL and applying an amount of delay corresponding to a given cycle of the multiplied clock output from the multiplier PLL so that a delayed signal has the same phase as the clock multiplied by the multiplier PLL;
generating a delay signal having a given amount of delay based on the amount of delay corresponding to the given cycle of the multiplied clock;
generating a delay control signal based on the delay signal having the given amount of delay; and
delaying an input signal based on the delay control signal.