Serializer/deserializer (SerDes) lanes with lane-by-lane datarate independence
First Claim
1. A circuit on a chip for serial data applications, the circuit comprising:
- a common phase-locked loop (PLL) having a multiplying factor, the common PLL configured to receive an off-chip reference clock signal generated external to the chip and produce an on-chip reference clock signal, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and
a plurality of serializer/deserializer (SerDes) lanes each including a respective transmitter, a respective receiver, and a respective fractional-N (frac-N) PLL including a respective divider with a respective divide value, the on-chip reference clock signal distributed to each respective frac-N PLL for use in generating a respective output clock signal with a respective frequency, the respective transmitter and receiver of each SerDes lane configured to operate at respective transmit and receive data rates that are based on the respective frequency and independent of data rates of other SerDes lanes of the plurality of SerDes lanes, the multiplying factor configured to suppress a portion of quantization noise, the portion introduced by modulating the respective divide value of the respective divider of each respective frac-N PLL of the plurality of SerDes lanes.
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Accused Products
Abstract
A circuit and method enables multiple serializer/deserializer (SerDes) data lanes of a physical layer device (PHY) to operate across a broad range of diversified data rates that are independent from lane to lane. The multiple SerDes data lanes may operate at data rates independent from one another. A single low frequency clock is input to the PHY. A frequency of the single low frequency clock is increased via a common integer-N phase-locked loop (PLL) on the PHY to produce a higher frequency clock. Each of the SerDes data lanes is operated, independently, as a fractional-N PLL that employs the higher frequency clock. Use of the common integer-N PLL enables modulation noise of the fractional-N PLLs to be suppressed by moving the modulation noise to higher frequencies where a level of the modulation noise is filtered, avoiding use of high risk noise cancellation techniques.
32 Citations
28 Claims
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1. A circuit on a chip for serial data applications, the circuit comprising:
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a common phase-locked loop (PLL) having a multiplying factor, the common PLL configured to receive an off-chip reference clock signal generated external to the chip and produce an on-chip reference clock signal, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and a plurality of serializer/deserializer (SerDes) lanes each including a respective transmitter, a respective receiver, and a respective fractional-N (frac-N) PLL including a respective divider with a respective divide value, the on-chip reference clock signal distributed to each respective frac-N PLL for use in generating a respective output clock signal with a respective frequency, the respective transmitter and receiver of each SerDes lane configured to operate at respective transmit and receive data rates that are based on the respective frequency and independent of data rates of other SerDes lanes of the plurality of SerDes lanes, the multiplying factor configured to suppress a portion of quantization noise, the portion introduced by modulating the respective divide value of the respective divider of each respective frac-N PLL of the plurality of SerDes lanes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for achieving serializer/deserializer (SerDes) lane datarate independence, the method comprising:
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producing an on-chip reference clock signal from a common phase-locked loop (PLL) having a multiplying factor, the common PLL on a chip, the on-chip reference clock signal produced based on an off-chip reference clock signal generated external to the chip, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and distributing the on-chip reference clock signal to each respective fractional-N (frac-N) PLL of a plurality of SerDes lanes each including a respective transmitter, a respective receiver, and a respective frac-N PLL including a respective divider with a respective divide value; modulating the respective divide value of the respective divider of each respective frac-N PLL of the plurality of SerDes lane, the multiplying factor configured to suppress a portion of quantization noise introduced by the modulating; generating a respective output clock signal with a respective frequency from each respective frac-N PLL based on the on-chip reference clock signal distributed; and operating each respective transmitter and receiver of each SerDes lane at respective transmit and receive data rates that are based on the respective frequency and independent of data rates of other SerDes lanes of the plurality of SerDes lanes. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A circuit on a chip for serial data applications, the circuit comprising:
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a common phase-locked loop (PLL), the common PLL configured to receive an off-chip reference clock signal generated external to the chip and produce an on-chip reference clock signal, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and a plurality of serializer/deserializer (SerDes) lanes each including a respective transmitter, a respective receiver, and a respective fractional-N (frac-N) PLL including a respective sigma-delta modulator, the on-chip reference clock signal distributed to each respective frac-N PLL for use in generating a respective output clock signal with a respective frequency, the respective transmitter and receiver of each SerDes lane configured to operate at respective transmit and receive data rates that are based on the respective frequency and independent of data rates of other SerDes lanes of the plurality of SerDes lanes, wherein each respective frac-N PLL of the plurality of SerDes lanes has an order that is lower relative to that of the respective sigma-delta modulator.
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24. A method for achieving serial/deserializer (SerDes) lane datarate independence, the method comprising:
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producing an on-chip reference clock signal from a common phase-locked loop (PLL) on a chip based on an off-chip reference clock signal generated external to the chip, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; distributing the on-chip reference clock signal to each respective fractional-N (frac-N) PLL of a plurality of SerDes lanes each including a respective transmitter, a respective receiver, and a respective frac-N PLL including a respective sigma-delta modulator, each respective frac-N PLL of the plurality of SerDes lanes configured to have an order that is lower relative to that of the respective sigma-delta modulator; generating a respective output clock signal with a respective frequency from each respective frac-N PLL based on the on-chip reference clock signal distributed; and operating each respective transmitter and receiver of each SerDes lane at respective transmit and receive data rates that are based on the respective frequency and independent of data rates of other SerDes lanes of the plurality of SerDes lanes.
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25. A circuit on a chip for serial data applications, the circuit comprising:
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a common phase-locked loop (PLL) having a multiplying factor, the common PLL configured to receive an off-chip reference clock signal generated external to the chip and to produce an on-chip reference clock signal, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and a serializer/deserializer (SerDes) lane, the SerDes lane including a fractional-N (frac-N) PLL, the frac-N PLL including a divider with a divide value, the on-chip reference clock signal distributed to the frac-N PLL, the multiplying factor configured to suppress a portion of quantization noise, the portion introduced by modulating the divide value of the divider of the frac-N PLL.
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26. A method comprising:
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producing an on-chip reference clock signal from a common phase-locked loop (PLL) having a multiplying factor, the common PLL on a chip, the on-chip reference clock signal produced based on an off-chip reference clock signal generated external to the chip, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; distributing the on-chip reference clock signal to a fractional-N (frac-N) PLL of a serializer/deserializer (SerDes) lane, the frac-N PLL including a respective divider with a respective divide value; modulating the divide value of the divider of the frac-N PLL of the SerDes lane, the multiplying factor configured to suppress a portion of quantization noise introduced by the modulating.
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27. A circuit on a chip for serial data applications, the circuit comprising:
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a common phase-locked loop (PLL), the common PLL configured to receive an off-chip reference clock signal generated external to the chip and to produce an on-chip reference clock signal, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and a serializer/deserializer (SerDes) lane including a fractional-N (frac-N) PLL, the frac-N PLL including a sigma-delta modulator, the on-chip reference clock signal distributed to the frac-N PLL, the frac-N PLL configured to have an order that is lower relative to that of the sigma-delta modulator of the frac-N PLL of the SerDes lane.
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28. A method comprising:
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producing an on-chip reference clock signal from a common phase-locked loop (PLL) on a chip based on an off-chip reference clock signal generated external to the chip, the on-chip reference clock signal higher in frequency relative to the off-chip reference clock signal; and distributing the on-chip reference clock signal to a fractional-N (frac-N) PLL of a serializer/deserializer (SerDes) lane, the frac-N PLL including a sigma-delta modulator, the frac-N PLL configured to have an order that is lower relative to that of the sigma-delta modulator of the frac-N PLL of the SerDes lane.
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Specification