CDR circuit including temperature sensor

Abstract

The present invention discloses a CDR circuit including a temperature sensor. In order to reduce the jitter of the CDR circuit without reducing the temperature coverage range, the present invention obtains the current temperature value through the temperature sensor, and before the frequency detection loop is locked, the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is locked to a first related value; when the frequency detection loop is locked, the locking of the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is unlocked, and the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is adjusted following the phase detection loop, and the current value of the output current of the charge pump in the phase detection loop is adjusted according to the second related value, so that the current value of the output current of the charge pump in the phase detection loop remains unchanged. The present invention avoids the problems of reduced temperature coverage and worsening signal jitter while reducing jitter. The present invention is suitable for the field of integrated circuits.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular to a CDR circuit including a temperature sensor. Background Art

[0002] Clock Data Recovery (CDR) circuits are often used in high-speed interconnect chips. After the signal is attenuated by channel propagation, it is recovered by the CDR circuit and sent to the subsequent circuit. The CDR circuit usually includes a frequency detection loop and a phase detection loop. Figure 1 The phase detection loop in the CDR circuit is demonstrated, including the phase detector, charge pump, low-pass filter and voltage-controlled oscillator, and finally the input data signal is sampled by the clock signal output by the voltage-controlled oscillator.

[0003] Since the signal after channel propagation attenuation has a lot of jitter, it needs to be retimed through the CDR circuit to recover the data. The frequency jitter of the clock signal output by the voltage-controlled oscillator in the CDR circuit directly determines the jitter of the recovered data. In other words, the jitter of the recovered data is determined by the jitter of the clock signal, so the jitter in the CDR circuit should be as small as possible.

[0004] In order to reduce the jitter of the clock signal in the CDR circuit, it is usually chosen to reduce the CDR loop bandwidth, and this is usually achieved by reducing the gain of the voltage-controlled oscillator or reducing the current of the charge pump, but they all have corresponding costs: reducing the gain of the voltage-controlled oscillator usually reduces the coverage of the CDR circuit lock frequency and narrows the temperature coverage range; reducing the current of the charge pump will increase the noise introduced by the charge pump current and thus worsen the jitter overall.

[0005] How to reduce the jitter of the CDR circuit while avoiding or alleviating the reduction of the temperature coverage range has become a difficult problem to be solved urgently in this field. Summary of the invention

[0006] In order to alleviate or partially alleviate the above technical problems, the solution of the present invention is as follows:

[0007] A CDR circuit including a temperature sensor, the CDR circuit including a phase detection loop and a frequency detection loop; obtaining a current temperature value through the temperature sensor; locking a voltage value of a voltage control signal of a voltage controlled oscillator in the phase detection loop to a first correlation value before the frequency detection loop is locked; unlocking the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop after the frequency detection loop is locked, the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is adjusted following the phase detection loop, and adjusting a current value of an output current of a charge pump in the phase detection loop according to a second correlation value, so that the current value of the output current of the charge pump in the phase detection loop remains unchanged; the first correlation value and the second correlation value are both related to the current temperature value.

[0008] Furthermore, the first correlation value is positively correlated with the relative position of the current temperature value in the set operating temperature range.

[0009] Furthermore, a second correlation value related to the current temperature value is obtained through the temperature sensor; after the frequency detection loop is locked, the current value of the output current of the charge pump in the phase detection loop is adjusted to a first current value according to the second correlation value, wherein the first current value is the current value of the output current of the charge pump in the phase detection loop when the frequency detection loop of the CDR circuit is locked.

[0010] Furthermore, the LOL signal indicates whether the frequency detection loop is locked.

[0011] Furthermore, the second correlation value is a value that changes with the current temperature value.

[0012] Further, the current value of the output current of the charge pump in the phase detection loop plus or minus the second correlation value is equal to the first current value.

[0013] Furthermore, the frequency detection loop is configured as follows: the data signal received from the channel and the clock signal output by the voltage-controlled oscillator are sent to the phase detector, and the output signal of the phase detector is used to control the charge pump; the output current of the charge pump passes through a low-pass filter to generate a voltage control signal for controlling the voltage-controlled oscillator.

[0014] Furthermore, the clock signal output by the voltage-controlled oscillator and the data signal received from the channel are used as input signals of the sampling circuit, and after being sampled by the sampling circuit, recovered data is obtained.

[0015] The technical solution of the present invention has one or more of the following beneficial technical effects:

[0016] (1) By reducing the gain of the voltage-controlled oscillator, the loop bandwidth of the CDR circuit is reduced, thereby reducing the jitter of the CDR circuit after locking, but it does not affect the temperature range covered by the phase detection loop in the CDR circuit.

[0017] (2) Ensure that the current in the phase detection loop of the CDR circuit remains essentially unchanged at any temperature, so that the jitter does not continue to deteriorate.

[0018] In addition, other beneficial effects of the present invention will be mentioned in the specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a phase detection loop in a CDR circuit in the prior art;

[0020] Figure 2 It is a phase detection loop in the improved CDR circuit of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same or similar items with substantially the same functions and effects. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order.

[0023] Figure 1 In the prior art, the phase detection loop in the CDR circuit usually sets the control signal of the voltage-controlled oscillator, that is, the output voltage signal of the low-pass filter, to the middle value of the adjustable range of the output voltage signal of the low-pass filter.

[0024] Therefore, no matter whether the ambient temperature is rising or falling, the voltage controlled oscillator can adjust the frequency of the output clock signal upward or downward to cover the ambient temperature. This means that the upper and lower halves of the adjustable output clock frequency range of the voltage controlled oscillator need to cover the high and low temperature variation ranges respectively.

[0025] Figure 2The phase detection loop in the improved CDR circuit of the present invention is shown. The data signal received from the channel and the clock signal output by the voltage-controlled oscillator are sent to the phase detector. The output signal of the phase detector is used to control the charge pump, and the output current of the charge pump passes through a low-pass filter to generate a voltage control signal for controlling the voltage-controlled oscillator. The voltage-controlled oscillator outputs a clock signal.

[0026] The clock signal and the data signal are also used as input signals of the sampling circuit, in which the output is the recovered data.

[0027] The present invention also designs a temperature sensor for sensing the ambient temperature. Specifically, the temperature sensor is used to monitor the operating temperature of the chip where the CDR circuit is located in real time.

[0028] Before the frequency detection loop of the CDR circuit is locked, a loop lock (Lock Of Loop, LOL) signal indicating whether the frequency detection loop in the CDR circuit is locked is at a high level, that is, the current frequency detection loop is not locked.

[0029] For example, the current temperature value is obtained through a temperature sensor.

[0030] Furthermore, a first correlation value related to the current temperature value is obtained through a temperature sensor. Preferably, the first correlation value is positively correlated with the relative position of the current temperature value in the set working temperature range. For example, if the set working temperature range is [T1, T2] and the current temperature value is Tc, the first correlation value V1=k×(Tc-T1) / (T2-T1), where T1 and T2 are the lowest working temperature and the highest working temperature, respectively, k is a coefficient indicating positive correlation, and (Tc-T1) / (T2-T1) indicates the relative position of the current temperature value in the set working temperature range.

[0031] Preferably, a second correlation value related to the current temperature value is obtained through a temperature sensor.

[0032] The first correlation value is used to adjust the voltage value of the voltage control signal of the voltage controlled oscillator, and the second correlation value is used to adjust the current value of the output current of the charge pump. In the present invention, the voltage control signal of the voltage controlled oscillator and the output current of the charge pump are both analog signals.

[0033] In the present invention, before the frequency detection loop of the CDR circuit is locked, the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is locked to the first relevant value. This step ensures the adjustment or coverage capability of the CDR circuit for temperature.

[0034] However, when the frequency detection loop of the CDR circuit is locked, the LOL signal becomes a low level, that is, the current frequency detection loop is locked, unlocking the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop. The voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop can be adjusted following the phase detection loop until the phase detection loop is finally locked.

[0035] Through the above configuration, the phase detection loop of the present invention can reduce the gain of the voltage-controlled oscillator and reduce the loop bandwidth of the CDR circuit, thereby reducing the jitter after the CDR circuit is locked, but ultimately does not affect the ability of the phase detection loop in the CDR circuit to cover the temperature range.

[0036] Furthermore, in a preferred embodiment, the current value of the output current of the charge pump is adjusted according to the second correlation value to ensure that the current in the phase detection loop of the CDR circuit remains substantially unchanged at any temperature, so that the jitter does not continue to deteriorate.

[0037] Preferably, after the frequency detection loop of the CDR circuit is locked, the current value of the output current of the charge pump in the phase detection loop is adjusted to a first current value according to the second correlation value, wherein the first current value is the current value of the output current of the charge pump in the phase detection loop when the frequency detection loop of the CDR circuit is locked. In other words, if the frequency detection loop of the CDR circuit is locked, the current current value of the output current of the charge pump in the phase detection loop also fluctuates with the fluctuation of the current temperature. The current current value of the output current of the charge pump in the phase detection loop plus or minus the second correlation value is equal to the first current value.

[0038] Furthermore, the second correlation value is a value that changes with the current temperature value.

[0039] That is, after the frequency detection loop of the CDR circuit is locked, the output current value of the charge pump in the phase detection loop is maintained unchanged by the technical means of the present invention. The beneficial effect of this embodiment is that the jitter of the clock signal generated by the CDR circuit will not be further deteriorated.

[0040] In order to better illustrate the present invention, numerous specific details are provided in the above specific embodiments. It should be understood by those skilled in the art that the present invention can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0041] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A CDR circuit including a temperature sensor, characterized in that: The CDR circuit includes a phase detection loop and a frequency detection loop; Obtaining the current temperature value through the temperature sensor; Before the frequency detection loop is locked, the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is locked to a first related value; When the frequency detection loop is locked, the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is unlocked, and the voltage value of the voltage control signal of the voltage controlled oscillator in the phase detection loop is adjusted following the phase detection loop, and, adjusting the current value of the output current of the charge pump in the phase detection loop according to the second correlation value so that the current value of the output current of the charge pump in the phase detection loop remains unchanged; The first correlation value and the second correlation value are both related to the current temperature value; The first correlation value is positively correlated with the relative position of the current temperature value in the set working temperature range; Obtaining a second correlation value related to the current temperature value through a temperature sensor; After the frequency detection loop is locked, adjusting the current value of the output current of the charge pump in the phase detection loop to a first current value according to the second correlation value, wherein the first current value is the current value of the output current of the charge pump in the phase detection loop when the frequency detection loop of the CDR circuit is locked; The clock signal output by the voltage-controlled oscillator and the data signal received from the channel are used as input signals of the sampling circuit, and after being sampled by the sampling circuit, the recovered data is obtained.

2. The CDR circuit including a temperature sensor according to claim 1, characterized in that: The LOL signal indicates whether the frequency detection loop is locked.

3. The CDR circuit including a temperature sensor according to claim 2, characterized in that: The second correlation value is a value that changes as the current temperature value changes.

4. The CDR circuit including a temperature sensor according to claim 3, characterized in that: The present current value of the output current of the charge pump in the phase detection loop plus or minus the second correlation value is equal to the first current value.

5. The CDR circuit including a temperature sensor according to claim 4, characterized in that: The frequency detection loop is configured as: The data signal received from the channel and the clock signal output by the voltage-controlled oscillator are fed into the phase detector, and the output signal of the phase detector is used to control the charge pump; The output current of the charge pump generates a voltage control signal after passing through a low-pass filter, which is used to control the voltage-controlled oscillator.

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