CN106788300B - System for automatic constant differential signal amplitude in high-speed serial interface - Google Patents

Abstract

The invention provides a system for automatically constant differential signal amplitude in a high-speed serial interface, which is used for constant input signal amplitude of an equalizer external to the system, ensures the equalization effect of the equalizer, and improves the integrity of the received signal. The system includes: a variable gain amplifier, which is used to receive the original differential signal and the control signal output by the gain control circuit, perform gain processing on the original differential signal, and output the differential signal after gain processing to an equalizer external to the system; The detection circuit is used to extract the amplitude of the differential signal after gain processing, and convert the amplitude into a voltage signal; the voltage comparator is used to compare the voltage signal with a reference voltage, and output a comparison result; the gain control circuit is used for A control code is determined according to the comparison result, and the control code is output to the variable gain amplifier as a control signal.

Description

System for Automatically Constant Differential Signal Amplitude in High Speed Serial Interfaces

technical field

The invention relates to the field of integrated circuit design related to the high-speed serial interface, in particular to a system for automatically constant differential signal amplitude in the high-speed serial interface.

Background technique

In a high-speed serial communication system, the low-pass characteristics of the channel greatly attenuate the high-frequency components of the serial signal, so an equalizer (CTLE) is required to compensate the high-frequency components of the signal, and due to channel impedance characteristics, circuit process deviations, and Affected by the environment and other factors, the amplitude of the serial signal will fluctuate greatly. If the signal amplitude is too large, it will reduce the CTLE equalization effect, and if it is too small, it will reduce the signal-to-noise ratio. The line signal is processed so that its amplitude is in the best input range of CTLE.

Contents of the invention

(1) Technical problems to be solved

The object of the present invention is to provide a system for automatically constant differential signal amplitude in high-speed serial interface, so as to solve at least one of the above technical problems.

(2) Technical solution

The present invention provides a system for automatically constant differential signal amplitude in a high-speed serial interface, including a variable gain amplifier, an amplitude detection circuit, a voltage comparator and a gain control circuit, wherein,

The variable gain amplifier is used to receive the original differential signal and the control signal output by the gain control circuit, perform gain processing on the original differential signal, and output the differential signal after gain processing to an equalizer external to the system;

An amplitude detection circuit, used to extract the amplitude of the differential signal after gain processing, and convert the amplitude into a voltage signal;

a voltage comparator, configured to compare the voltage signal with a reference voltage, and output a comparison result;

The gain control circuit is used to determine the control code according to the comparison result, and output the control code as a control signal to the variable gain amplifier.

Preferably, the reference voltage varies with the characteristics of the equalizer in the system.

Preferably, the amplitude of the differential signal after gain processing is controlled by a control code, and the value of the control code is positively related to the amplitude of the output signal, and the range of the control code is 0 to 2 ^N-1 , where N is the gain control The bit width of the port.

Preferably, the gain control circuit includes:

a comparison result input terminal for receiving the comparison result;

A group of gain control ports, used to connect the variable gain amplifier to control its gain;

An end signal output terminal is used to connect with the voltage comparator and the power control port of the amplitude detection circuit.

Preferably, the variable gain amplifier includes:

A pair of first differential signal input terminals, used to receive the original differential signal;

A pair of differential signal output terminals for outputting differential signals after gain processing;

A set of gain control signal input terminals is used for inputting control codes.

Preferably, the amplitude detection circuit includes:

A group of second differential signal input terminals, used to receive differential signals after gain processing;

An amplitude voltage output terminal is connected to the positive terminal of the voltage comparator for outputting the extracted differential signal amplitude;

A first power control terminal is used to turn on or turn off the power of the amplitude detection circuit.

Preferably, the voltage comparator includes:

The positive input terminal is used to connect with the amplitude voltage output terminal of the amplitude detection circuit;

The negative input terminal is used to connect to the reference voltage;

The output end is used to connect with the gain control circuit;

A second power control terminal is used to turn on or turn off the power of the voltage comparator.

(3) Beneficial effects

The invention adopts a variable gain amplifier, an amplitude detection circuit, a voltage comparator and a gain control circuit to realize the automatic constant input amplitude of the equalizer external to the system, ensuring that the input amplitude of the equalizer is consistent with the reference voltage amplitude, and ensuring Equalization effect improves signal integrity.

The present invention also adopts a power control terminal, which is adjusted only for a short period of time after power-on, and related circuits enter into a shutdown state after adjustment, without introducing excessive power consumption.

Description of drawings

Fig. 1 is the system for automatically constant differential signal amplitude in the high-speed serial interface of the embodiment of the present invention;

FIG. 2 is a working flowchart of the gain control circuit of the embodiment of the present invention.

Detailed ways

An embodiment of the present invention provides a system for automatically constant differential signal amplitude in a high-speed serial interface, including a variable gain amplifier, an amplitude detection circuit, a voltage comparator, and a gain control circuit, wherein,

The variable gain amplifier is used to receive the original differential signal and the control signal output by the gain control circuit, perform gain processing on the original differential signal, and output the differential signal after gain processing to the equalizer external to the system; the amplitude of the differential signal after gain processing The value is controlled by the control code, and the control code value has a positive relationship with the output signal amplitude. The control code ranges from 0 to 2 ^N-1 , where N is the bit width of the gain control port. The larger the N value, the greater the system control The higher the accuracy is, the closer the amplitude of the differential signal after the circuit adjustment and output after gain processing is to the amplitude of the reference voltage.

Specifically, the variable gain amplifier includes: a pair of first differential signal input terminals, used to receive the original differential signal; a pair of differential signal output terminals, used to output the differential signal after gain processing; a set of gain control signal input terminal for inputting control codes.

The amplitude detection circuit is used to extract the amplitude of the differential signal after gain processing, and convert the amplitude into a voltage signal; it includes: a set of second differential signal input terminals, used to receive the differential signal after gain processing; an amplitude The value voltage output terminal is connected to the positive terminal of the voltage comparator for outputting the extracted differential signal amplitude; a first power supply control terminal is used for turning on or off the power supply of the amplitude detection circuit.

A voltage comparator, used to compare the voltage signal with a reference voltage, and output a comparison result; the reference voltage changes with the characteristics of the equalizer, including: a positive input terminal, used to communicate with the amplitude voltage of the amplitude detection circuit The output terminal is connected; the negative input terminal is used for connecting the reference voltage; the output terminal is used for connecting with the gain control circuit; a second power supply control terminal is used for turning on or off the power supply of the voltage comparator.

The gain control circuit is used to determine the control code according to the comparison result, and output the control code as a control signal to the variable gain amplifier. Specifically, the gain control circuit includes: a comparison result input terminal for receiving the comparison result; a group of gain control ports for connecting to a variable gain amplifier to control its gain; an end signal output terminal, It is used to connect with the power control port of the voltage comparator and the amplitude detection circuit.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Fig. 1 is the system for automatic constant differential signal amplitude in the high-speed serial interface of the embodiment of the present invention, as shown in Fig. 1, this system comprises: variable gain amplifier, is used for receiving original differential signal and gain control circuit output The control signal is used to perform gain processing on the original differential signal, and output the differential signal after gain processing to the equalizer external to the system; the amplitude detection circuit is used to extract the amplitude of the differential signal after gain processing, and convert the amplitude to is a voltage signal; a voltage comparator, used to compare the voltage signal with a reference voltage, and output a comparison result; a gain control circuit, used to determine a control code according to the comparison result, and output the control code as a control signal to the variable gain amplifier.

The variable gain amplifier includes: a pair of first differential signal input terminals for receiving the original differential signal v _in ; a pair of differential signal output terminals for outputting a gain-processed differential signal v _out , and the output differential signal is divided into There are two channels, one is connected to an external equalizer to realize the subsequent processing of the differential signal, and the other is connected to the input terminal DIFin of the amplitude detection circuit; a set of gain control signal input terminals is connected to the gain control port Gain-code of the gain control circuit for input control code K, and use K as a control signal. The bit width of the input terminal of the control signal is N, and the larger the value of N, the higher the system control precision, and the closer the amplitude of the differential signal after the circuit adjustment and output gain processing is to the reference voltage amplitude. The minimum value of the control code is K=0, and the maximum value is K=2 ^N -1. The variable gain amplifier realizes the gain processing of the input differential signal, and the amplitude of the output differential signal after gain processing is controlled by the control code K. When the value of the input control code K is larger, the output signal amplitude is larger, and vice versa. .

The amplitude detection circuit is used to extract the amplitude of the gain-processed differential signal, and convert the amplitude into a voltage signal output, including: a set of second differential signal input terminals for receiving the gain-processed Differential signal v _out ; an amplitude voltage output terminal PEAK is connected to the positive terminal of the voltage comparator for outputting the extracted differential signal amplitude; a first power control terminal PD 1 is used for turning on or off the power supply of the amplitude detection circuit .

The voltage comparator is used to realize the comparison between the output voltage signal of the amplitude detection circuit and the reference voltage, including: a positive input terminal for connecting with the amplitude voltage output terminal PEAK of the amplitude detection circuit; a negative input terminal for connecting the reference voltage Voltage VREF, VREF is obtained according to the characteristics of the equalizer, when the equalizer input signal amplitude is near VREF, the equalizer has the best equalization effect; the output terminal is used to connect with the RESULT port of the gain control circuit; when the amplitude detection circuit outputs the voltage When the voltage is higher than the reference voltage, the output of the voltage comparator is 1; when the output voltage of the amplitude detection circuit is lower than the reference voltage, the output of the voltage comparator is 0; a second power supply control terminal PD 2 is used to turn on or off the voltage comparator power supply.

The gain control circuit includes: a comparison result input terminal RESULT for receiving the comparison result; a group of gain control ports Gain-code, with a bit width of N, for connecting to a variable gain amplifier to control its gain; An end signal output terminal FINISH is used for connecting with the power supply control port of the voltage comparator and the amplitude detection circuit. The gain control circuit outputs the control code to control the variable gain amplifier according to the output result of the voltage comparator, and turns off the power supply of the voltage comparator and the amplitude detection circuit after the adjustment is completed, so that the gain-processed difference output by the variable gain amplifier The amplitude of the signal is substantially constant at the amplitude of the reference voltage.

Fig. 2 is the working flow diagram of the gain control circuit of the embodiment of the present invention, as shown in Fig. 2, the moment the gain control circuit is powered on, the gain control circuit resets, the gain control code K returns to zero, and the adjustment end signal FINISH is set to 0, at this time The voltage comparator and the amplitude detection circuit are powered on. At this time, the variable gain amplifier amplifies the input original differential signal v _in according to the minimum amplification factor, and the amplitude detection circuit extracts the gain-processed differential signal v output by the variable gain amplifier. The amplitude of _out is compared with the reference voltage VREF by the voltage comparator. If the comparison result is 1 at this time, it means that the signal amplitude after gain processing has been greater than the reference voltage, and the circuit adjustment process is over. If the comparison result is not 1 , the gain control code is increased by 1, the gain of the corresponding variable gain amplifier is increased by one level, and the original signal is subjected to gain processing, and the amplitude of the processed signal output is also increased by one level. Before the gain control code reaches the maximum value, if the gain The amplitude of the processed differential signal does not reach the level of VREF, the gain control code continues to increase, and the amplitude of the signal after gain processing continues to increase until the amplitude reaches the level of VREF, so that the voltage comparator comparison result RESULT is 1. At this time, the gain control circuit fixes the output gain control code, and the gain of the variable gain amplifier is also fixed. At this time, its output amplitude is closest to the reference voltage VREF. In the process of circuit adjustment, if the gain control code reaches the maximum value of 2 ^N-1 , the differential signal amplitude after gain processing still cannot reach the level of the reference voltage, then the adjustment process ends directly, and the variable gain amplifier operates according to the maximum K value of 2 ^{N -1} for amplification, the output signal amplitude at this time is also the level closest to VREF within the allowable range of circuit performance. After the adjustment process is over, the FINISH signal is set to 1, and the voltage comparator and the amplitude detection circuit are powered off to save power consumption. In summary, this structure can keep the amplitude of the input signal of the equalizer at the level closest to VREF within the allowable range of the circuit performance, and enable the circuit to obtain the most suitable amplitude, and the appropriate amplitude can obtain the best equalizer equalization The effect ensures the best signal integrity of the interface, the power is automatically turned off after the adjustment, and the power consumption is not significantly increased on the basis of achieving a constant amplitude.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (5)

1. A system for automatic constant differential signal amplitude in a high-speed serial interface, characterized in that it comprises a variable gain amplifier, an amplitude detection circuit, a voltage comparator and a gain control circuit, wherein, The variable gain amplifier is used to receive the original differential signal and the control signal output by the gain control circuit, perform gain processing on the original differential signal, and output the differential signal after gain processing to an equalizer external to the system; An amplitude detection circuit, used to extract the amplitude of the differential signal after gain processing, and convert the amplitude into a voltage signal; a voltage comparator, configured to compare the voltage signal with a reference voltage, and output a comparison result; a gain control circuit, configured to determine a control code according to the comparison result, and output the control code as a control signal to the variable gain amplifier; Wherein, the reference voltage changes as the characteristics of the equalizer change; Wherein, the differential signal amplitude after the gain processing is controlled by a control code, and the control code value has a positive relationship with the output signal amplitude, and the control code ranges from 0 to 2 ^N-1 , where N is a gain control port bit width; Wherein, the control code starts from 0, and increases by 1 in turn, until the voltage comparator compares and obtains that the voltage signal is higher than the reference voltage, the control code is fixed at the current value; wherein, when the control code reaches the maximum value 2 ^N-1 , and When the voltage signal is still lower than the reference voltage, the control code is fixed at the maximum value. 2. The system according to claim 1, wherein the gain control circuit comprises: a comparison result input terminal for receiving the comparison result; A group of gain control ports, used to connect the variable gain amplifier to control its gain; An end signal output terminal is used to connect with the voltage comparator and the power control port of the amplitude detection circuit. 3. The system according to claim 1, wherein the variable gain amplifier comprises: A pair of first differential signal input terminals, used to receive the original differential signal; A pair of differential signal output terminals for outputting differential signals after gain processing; A set of gain control signal input terminals is used for inputting control codes. 4. The system according to claim 1, wherein the amplitude detection circuit comprises: A group of second differential signal input terminals, used to receive differential signals after gain processing; An amplitude voltage output terminal connected to the positive input terminal of the voltage comparator for outputting the extracted differential signal amplitude; A first power control terminal is used to turn on or turn off the power of the amplitude detection circuit. 5. The system of claim 1, the voltage comparator comprising: The positive input terminal is used to connect with the amplitude voltage output terminal of the amplitude detection circuit; The negative input terminal is used to connect to the reference voltage; The output end is used to connect with the gain control circuit; A second power control terminal is used to turn on or turn off the power of the voltage comparator.