Electronic device and method for on chip jitter measurement
View Patent ↗The present invention relates to an integrated electronic device for digital signal processing, which includes a reference clock input for receiving a reference clock, a phase locked loop (PLL), a phase interpolator (PI) coupled to the phase locked loop (PLL) for shifting a phase of an output clock signal of the PLL in a stepwise manner so as to generate a shifted output clock signal (PHI_out), a logic stage for determining the state of the reference clock signal (REF_CLK) multiple times during an edge of the shifted output clock for each phase shift, a storing means for storing information whether or not the determined state of the reference clock signal (REF_CLK) is stable for a phase of the shifted output clock signal (PHI_out), and an interface configured to read out the stored information for determining the jitter of the shifted output clock signal (PHI_OUT).
1. An integrated electronic device for digital signal processing comprising:
a reference clock input for receiving a reference clock;
a phase locked loop (PLL);
a phase interpolator (PI) coupled to the phase locked loop (PLL) for shifting a phase of an output clock signal of the PLL in a stepwise manner so as to generate a shifted output clock signal (PHI_out);
a logic stage for determining the state of the reference clock signal (REF_CLK) multiple times during an edge of the shifted output clock for each phase shift;
a storing means for storing information whether or not the determined state of the reference clock signal (REF_CLK) is stable for a phase of the shifted output clock signal (PHI_out); and
an interface configured to read out the stored information for determining the jitter of the shifted output clock signal (PHI_OUT).
2. The integrated electronic device according to claim 1 , wherein the storage means further comprises means for storing a first logic value if the state of the reference clock signal is the same for all the multiple measurements relating to one phase of the shifted output clock signal; and means for storing a second logic value if the state of the reference clock signal is not the same for all the multiple measurements relating to one phase of the shifted output clock signal.
3. The integrated electronic device according to claim 1 , wherein the interface is a serial interface.
4. A method for determining the jitter of a phase locked loop comprising:
generating a clock signal with a phase locked loop in an integrated circuit;
generating a shifted output clock signal having a plurality of phases spanning a period of the clock signal;
determining the state of a reference clock signal during the edges of the shifted output clock signal multiple times for each phase of the shifted output signal;
storing a first logic value if the state of the reference clock signal is the same for all the multiple measurements relating to one phase of the shifted output clock signal; or
storing a second logic value if the state of the reference clock signal is not the same for all the multiple measurements relating to one phase of the shifted output clock signal; and
determining the phase jitter of the shifted output clock signal of the PLL based on the second logic values.