TW201624445A - Method for adjusting terminal impedance - Google Patents

Abstract

A method for adjusting terminal impedance is provided, which is adapted for adjusting a terminal impedance of a differential signal receiver, and the adjusting method comprises the following steps. A current value of a differential signal flowing though the terminal impedance is detected by a current detecting circuit. Characteristic points of the differential signals are determined by a micro controller according to the current value of the differential signal. A distortion status of the differential signal is determined by the micro controller according to the characteristic points. An impedance value of the terminal impedance is adjusted by the micro controller according to the distortion status of the differential signal.

Description

Terminal impedance adjustment method

The present invention relates to an impedance adjustment method, and more particularly to a terminal impedance adjustment method for a differential signal receiver.

In recent years, due to the increase in panel resolution, in response to the large amount of data transmission requirements of high-resolution panels, the transmission interface of panel drivers must use a high-speed data transmission interface. However, the high-speed signal data transmission interface is susceptible to interference from the trace impedance and signal routing methods. For the differential signal receiver, the high-speed signal data transmission interface has strict requirements on the impedance matching of the trace and the impedance matching of the terminal impedance.

Although the equivalent impedance of the trace can be controlled by the trace layout and the process parameters of the printed circuit board to achieve impedance matching, the equivalent impedance of the trace may still be affected by, for example, conductor film thickness tolerance, substrate thickness. Tolerance, bonding contact resistance, etc. are not affected by the factors, resulting in equivalent impedance offset and discontinuity, which in turn causes signal distortion and causes the display to display image errors. Therefore, how to effectively improve signal distortion becomes an important issue in the signal transmission interface.

The invention provides a terminal impedance adjustment method for determining a signal distortion state according to a signal current value flowing through a terminal impedance, and adjusting a terminal impedance according to a distortion state to improve signal distortion.

The terminal impedance adjustment method of the present invention is suitable for adjusting the terminal impedance of the differential signal receiver, and the terminal impedance adjustment method comprises the following steps. The current value of the differential signal flowing through the terminal impedance is detected by the current detecting circuit. The plurality of feature points of the differential signal are determined by the microcontroller according to the current value of the differential signal, and the distortion state of the differential signal is determined according to the feature points, and the impedance value of the terminal impedance is adjusted according to the distortion state of the differential signal.

Based on the above, the terminal impedance adjustment method according to the embodiment of the present invention determines the distortion state of the differential signal according to the current value of the differential signal flowing through the terminal impedance, and thereby adjusts the terminal impedance. In this way, the signal integrity can be ensured, thereby improving signal distortion and causing display screen errors.

The above described features and advantages of the invention will be apparent from the following description.

10‧‧‧Transport interface

100‧‧‧Differential Signal Receiver

110‧‧‧Amplifier

130‧‧‧Signal improvement circuit

131, 133‧‧‧ current detection circuit

135‧‧‧Microcontroller

137‧‧‧Switch controller circuit

150‧‧‧Transmission line end

S310~S370, S510~S590, S605~S690‧‧‧ steps

a~h‧‧‧ feature points

C‧‧‧ capacitor

DSI+, DSI-‧‧ ‧ differential signal

Ip1, Ip21‧‧‧ current

Rs, Rs1, Rs2‧‧‧ transmission line impedance

Rp, Rp1, Rp2‧‧‧ terminal impedance

SW1, SW2‧‧‧ switch control signal

t _f , t _flat , t _r ‧‧‧ time threshold

V _swing ‧‧‧Swing voltage

V+, V-‧‧‧ voltage

1 is a circuit diagram of a transmission interface in accordance with an embodiment of the present invention.

2 is a schematic diagram showing a detailed circuit of a signal improving circuit according to an embodiment of the invention. Figure.

FIG. 3 is a flow chart illustrating a method for adjusting a terminal impedance according to an embodiment of the invention.

4 is an example of a digital current signal waveform of a differential signal.

Figure 5 is a flow chart for impedance matching in the initial stage.

Figure 6 is a flow chart for periodically performing impedance matching.

1 is a circuit diagram of a transmission interface in accordance with an embodiment of the present invention. Referring to FIG. 1 , in the embodiment, the transmission interface 10 includes a differential signal receiver 100 and a transmission line end 150 . The differential signal receiver 100 includes, for example, a comparator 110 and a signal improving circuit 130 having a terminal impedance Rp. The differential signal receiver 100 of the embodiment of the present invention can be applied to a driving circuit controller, a control chip or a control circuit of a display such as a liquid crystal display (LCD), an organic light emitting display (OLED) or the like. However, the embodiments of the present invention are not limited thereto.

In this embodiment, the differential signals DSI+, DSI- are transmitted by a system (for example, a central processing unit (CPU), a microprocessor, etc.), and then transmitted to the transmission line of the transmission line end 150 to the transmission line. The differential signal receiver 100, wherein the transmission lines of the transmission line ends 150 form equivalent impedances Rs1, Rs2. When the differential signals DSI+, DSI- are transmitted to both ends of the terminal impedance Rp of the signal improving circuit 130, voltages V+ and V- are respectively formed across the terminal impedance Rp to form a voltage difference, and are provided through the output of the comparator 110. Corresponding data signal SDD.

FIG. 2 is a detailed circuit diagram of the signal improving circuit 130 according to an embodiment of the invention. Please refer to FIG. 1 and FIG. 2, wherein the same or similar elements are given the same or similar reference numerals. In the present embodiment, the signal improving circuit 130 includes, for example, terminal impedances Rp1, Rp2, current detecting circuits 131, 133, a microcontroller 135, and a switch controller circuit 137. Among them, the terminal impedances Rp1 and Rp2 connected in series are equivalent to the terminal impedance Rp (that is, Rp=Rp1+Rp2). The terminal impedance Rp1 receives the current Ip1 of the differential signal DSI+. The terminal impedance Rp2 receives the current Ip2 of the differential signal DSI-. The current detecting circuit 131 is coupled to the terminal impedance Rp1 to measure the current Ip1, and the current detecting circuit 133 is coupled to the terminal impedance Rp2 to measure the current Ip2. The terminal impedances Rp1 and Rp2 are, for example, variable resistors. The microcontroller 135 can determine the distortion states of the differential signals DSI+ and DSI- according to the currents Ip1 and Ip2, and then control the switch controller circuit 137 according to the distortion states of the differential signals DSI+ and DSI-. The corresponding switch control signals SW1 and SW2 are provided to adjust the impedance values of the terminal impedances Rp1 and Rp2.

In an embodiment of the invention, the terminal impedances Rp1, Rp2 may be formed by a transistor, and the current detecting circuits 131, 133 may include a current mirror to respectively replicate the current Ip1 flowing through the terminal impedances Rp1, Rp2. Ip2, but in other embodiments, the current detecting circuits 131, 133 may include other components or circuits that can detect the currents Ip1, Ip2.

FIG. 3 is a flow chart illustrating a method for adjusting a terminal impedance according to an embodiment of the invention. Referring to FIG. 3, the operation method of this embodiment can be applied to the transmission interface 10 of FIG. 1 and the signal improvement circuit 130 of FIG. Hereinafter, the components or modules in the transmission interface 10 and the signal improvement circuit 130 are described in the terminal of the embodiment of the present invention. Impedance adjustment method. The various processes of the method can be adjusted accordingly according to the implementation situation, and are not limited thereto.

In step S310, the permeation current detecting circuits 131 and 133 respectively detect current values (for example, current values of the currents Ip1 and Ip2) of the differential signals DSI+ and DSI− flowing through the terminal impedances Rp1 and Rp2. For the method of detecting the current value by the current detecting circuits 131 and 133, refer to the detailed description of the current detecting circuits 131 and 133 in FIG. 2, and details are not described herein again. In some embodiments, the currents Ip1, Ip2 can further convert the analog current value into a digital current value via an analog-to-digital converter (ADC) (not shown), and then pass through the digital current register. The digital current is transmitted to the microcontroller 135 (not shown).

In step S330, the micro-controller 135 determines the feature points of the differential signals DSI+ and DSI- based on the current values of the differential signals DSI+ and DSI-. Specifically, the microcontroller 135 can obtain the signal strengths of the differential signals DSI+ and DSI- and the appearance of the signal waveform according to the current values of the differential signals DSI+ and DSI- obtained in step S310, and the microcontroller 135 can The feature points of the differential signals DSI+ and DSI- are determined based on the signal waveform.

In an embodiment of the invention, the feature point feature points of the differential signals DSI+, DSI- are, for example, waveform inflection points of the differential signals DSI+, DSI-. For example, FIG. 4 is an example of a digital current signal waveform of the differential signals DSI+, DSI-. The microcontroller 135 determines the feature points a to h by judging the digital current value. When the microcontroller 135 determines the change in the decrement of the differential signal DSI+ based on the digital current value, the microcontroller 135 defines this waveform turning point as the feature point a. When the differential signal DSI+ is decremental When the change is gradual, the microcontroller 135 defines this waveform turning point as the feature point d. When the differential signal DSI+ produces an incremental change, the microcontroller 135 defines this waveform turning point as the feature point f. When the differential signal DSI+ generation changes from a progressive change to a gradual change, the microcontroller 135 defines this waveform turning point as the feature point g. By analogy, the microcontroller 135 can also determine the feature points b, c, e, h of the differential signal DSI - on the signal waveform.

Next, in step S350, the micro-controller 135 determines the distortion states of the differential signals DSI+ and DSI- based on the feature points. In an embodiment, the microcontroller 135 calculates the swing voltage, the falling transient time, the level hold time, and the rising transient time of the differential signals DSI+, DSI- according to the feature points, and according to the swing voltage, the falling transient time, The level retention time and the rising transient time determine the distortion state.

In this embodiment, the microcontroller 135 counts the time difference of the temporally adjacent feature points among the feature points through a clock counter (not shown) to obtain the falling transient time, the level holding time, and the rising transient time.

4 is used as an example. When the microcontroller 135 defines the feature point a, the clock counter starts to accumulate the clock count value. Each time a clock passes (for example, after 3 microseconds (μs), 500 milliseconds (ms), etc.), the clock counter increments the clock count by one until the microcontroller 135 determines the next feature point (ie Feature point d). When the microcontroller 135 determines the feature point d, the clock counter no longer accumulates the clock count value, and uses the current pulse count value as the time difference t _ad from the feature point a to the feature point d (t _ad = t _d -t _a ). By analogy, the clock counter can obtain the time difference t _df (t _df =t _f -t _d ), t _fg (t _fg =t _g -t _f ), t _bc (t ) of the feature points adjacent to each other in time series. _Bc = t _{c -} t _b ), t _ce (t _ce = t _{e -} t _c ) and t _eh (t _eh = t _{h -} t _e ). Next, the microprocessor 135 can convert the digital time differences t _ad , t _df , t _fg , t _bc , t _{ce ,} and t _eh with the clock operating frequency (eg, 200 megahertz (MHz), 500 MHz, etc.) operating time. Then to get the analog time to represent the value. For example, the time difference t _ad corresponds to a count value of 3, and the clock operation frequency is 500 MHz, and the analog time of the time difference t _ad represents a value of 6 μs.

Thereafter, the microcontroller 135 can use, for example, the analog time representation values of the digital time differences t _ad , t _eh as the falling transient time, the analog time representation values of the digital time differences t _ce , t _df as the level holding time, and the digital time difference t The analog time of _bc and t _fg represents the value as the rising transient time. In other embodiments, the micro-controller 135 or directly to the digital time difference t _ad, t _eh as fall transient time, the number of bit time difference t _ce, the holding time t _df as the level, and the number of bit time difference t _bc, t _fg as increased Transient time.

Further, the microcontroller 135 calculates the voltage difference of the feature points at the same time point among the feature points to obtain the wobble voltage. Taking FIG. 4 as an example, the feature points c and d are feature points at the same time point, and the microcontroller 135 first calculates the current values I _c and I _d of the feature points c and d, and then according to the currents of the feature points c and d. The impedance values of the values I _c and I _d and the terminal impedances Rp1 and Rp2 are used to estimate the voltage of each characteristic point, thereby obtaining the wobble voltage V _swing . For example, the voltage difference V _cd =|V _d -V _c |. The microcontroller 135 can select these voltage differences V _cd as the wobble voltage V _swing . By analogy, the microcontroller 135 can calculate the voltage differences V _ab , V _{ef ,} and V _gh . In other embodiments, the microcontroller 135 can choose these voltage difference V _cd, V _ab, V _ef and V _gh one wherein the voltage difference V _cd, V _ab, V _ef and V _gh average value or a voltage difference The weighted average of V _cd , V _ab , V _{ef ,} and V _gh is taken as the swing voltage V _swing , and is not limited thereto.

The calculated voltage swing down transient time, hold time and the level after the rise time of the transient, the micro-controller 135 comparing the voltage swing V _swing threshold voltage V _threshold, comparing transient fall time, hold time and increased level Transient time and corresponding time thresholds t _f , t _flat and t _r . When the swing voltage V _swing is equal to the voltage threshold V _threshold and the falling transient time (eg, t _ad ) is approximately equal to the time threshold t _f , the level hold time (eg, t _df ) is approximately equal to the time threshold t _flat and the rising transient time (e.g., t _fg ) is substantially equal to the time threshold value t _r , and the microcontroller 135 determines that the distortion states of the differential signals DSI+, DSI- are in a distortion-free state. When the wobble voltage V _{swing is} less than the voltage threshold V _threshold , the descent transient time (eg, t _ad ) is less than the time threshold t _{f ,} and the rising transient time (eg, t _fg ) is less than the time threshold t _r , the microcontroller 135 It is judged that the distortion state of the differential signals DSI+ and DSI- is the signal attenuation state. When the swing voltage V _{swing is} greater than the voltage threshold V _threshold , the falling transient time (eg, t _ad ) is greater than the time threshold t _{f ,} and the rising transient time (eg, t _fg ) is greater than the time threshold t _r , the microcontroller 135 It is judged that the distortion state of the differential signals DSI+ and DSI- is the signal amplification state.

It should be noted that the threshold voltage V _threshold and the time threshold t _f, t _flat and t _r may be set in advance or according to the requirement of practical application changes. In addition, the microcontroller 135 can define a voltage threshold V _threshold and time thresholds t _f , t _{flat ,} and t _r for the differential signal receiver 100 signal waveform distortion tolerance.

For example, taking FIG. 4 as an example, assuming that the voltage difference V _{cd is} used as the wobble voltage V _swing , the wobble voltage V _swing will be approximately equal to the voltage threshold V _threshold , and the time differences t _ad , t _eh will be approximately equal to the time threshold t _f , the time difference t _ce , t _df will be approximately equal to the time threshold t _flat , and the time difference t _bc , t _fg will be approximately the time threshold equal to t _r . The microcontroller 135 can determine that the distortion state is a distortion free state.

Next, in step S370, the impedance value of the terminal impedance is adjusted by the microcontroller 135 according to the distortion state of the differential signal. In the present embodiment, when the distortion state is the distortionless state, the impedance value of the terminal impedance is not adjusted. When the distortion state is the signal attenuation state, the impedance value of the terminal impedance is increased. When the distortion state is the signal amplification state, the impedance value of the terminal impedance is lowered.

Specifically, when the distortion state is the distortionless state, the microcontroller 135 determines that the terminal impedances Rp1, Rp2 match the transmission line impedances Rs1, Rs2, and does not need to adjust the impedance values of the terminal impedances Rp1, Rp2. When the distortion state is the signal attenuation state, the microcontroller 135 determines that the terminal impedances Rp1 and Rp2 are smaller than the transmission line impedances Rs1 and Rs2, and the impedance values of the terminal impedances Rp1 and Rp2 need to be increased to make the terminal impedances Rp1 and Rp2 equal ( Or similar to the transmission line resistances Rs1, Rs2. Moreover, when the distortion state is the signal amplification state, the microcontroller 135 determines that the terminal impedances Rp1 and Rp2 are greater than the transmission line impedances Rs1 and Rs2, and the impedance values of the terminal impedances Rp1 and Rp2 need to be lowered to make the terminal impedances Rp1 and Rp2. Equal to (or approximate to) the transmission line impedances Rs1, Rs2.

In an embodiment of the invention, the microcontroller 135 can perform a comparison operation on the data values of the respective stages of the time differences t _ad , t _df , t _fg and the voltage difference V _cd and the corresponding threshold values, and is operated by the microcontroller 135. The step value can be obtained later. This switch step value is the switch control signals SW1, SW2 in the switch control circuit 137 of FIG. The microcontroller 135 controls the impedance values of the terminal impedances Rp1 and Rp2 through the switch control signals SW1 and SW2, thereby adjusting and controlling the signal waveform of the differential signal receiver 100 to achieve t _ad ≒t _f , t _df ≒t _flat , t _fg ≒t _r and V _cd ≒V _threshold . For example, the switch control signal SW1 has switch step values SW1 ₁ , SW1 ₂ , SW1 ₃ , SW1 ₄ , SW1 ₅ , which respectively correspond to impedance values of different magnitude terminal impedances Rp1.

Further, the adjustment flow of the terminal impedances Rp1, Rp2 of the present invention has two mode settings. In one embodiment, when the differential signal receiver 100 is initialized, the current detecting circuits 131, 133 detect the current values Ip1, Ip2 of the differential signals DSI+, DSI- flowing through the terminal impedances Rp1, Rp2. When the differential signal receiver 100 completes initialization, the control current detecting circuits 131, 133 stop detecting the current value of the differential signal flowing through the terminal impedance. In other words, the impedance matching adjustment is automatically performed in the initial state of the differential signal receiver 100, for example, in the power-on state, to receive the differential signals DSI+, DSI- according to the impedance values of the adjusted terminal impedances Rp1, Rp2.

For example, Figure 5 is a flow chart for impedance matching in the initial stage. Referring to FIG. 1 and FIG. 5, after the differential signal receiver 100 is activated, the currents Ip1 and Ip2 are obtained by the current detecting circuits 131 and 133 (step S510), and the operations are performed by the microcontroller 135 to obtain the currents Ip1 and Ip2. The signal strength and the signal waveform appearance (step S530) are taken to obtain, for example, the time differences t _ad , t _df , t _fg and the voltage difference V _cd of FIG. 4 . Next, the time difference t _ad , t _df , t _fg and the voltage difference V _{cd are} compared with the time thresholds t _f , t _flat and t _r and the voltage threshold V _{threshold by the} microcontroller 135 (step S550). If they are substantially equal, it is not necessary to adjust the impedance values of the terminal impedances Rp1 and Rp2, and then the process returns to S510 to wait for the next detection current time, for example, the differential signal receiver 100 performs initialization or the next detection cycle. If they are not equal, the switching step values of the switch control signals SW1, SW2 are generated by the microcontroller 135 and calculated based on the comparison result (step S570). Finally, the impedance values of the terminal impedances Rp1 and Rp2 are adjusted by the switch control circuit 137 and according to the switching step values of the switch control signals SW1 and SW2 (step S590).

In another embodiment, during each detection period, the current detecting circuits 131 and 133 are configured to detect the current values Ip1 and Ip2 of the differential signals DSI+ and DSI- flowing through the terminal impedances Rp1 and Rp2. In other words, the embodiment of the present invention can periodically perform impedance matching adjustment during signal transmission to continuously maintain the integrity of the signal, and the periodicity can be in units of frames.

For example, FIG. 6 is a flow chart for performing impedance matching periodically. Referring to FIG. 1 and FIG. 6, the detection period of the current detecting circuits 131 and 133 (for example, two picture frames, five picture frames, etc.) is set by the microcontroller 135 (step S605), and the function includes the differential signal. The receiver 100 performs impedance matching control after being activated, and can also perform current detection by setting the detection period. Steps S610 to S690 can be described with reference to steps S510 to S590 in FIG. 5, and details are not described herein again. Through the periodic control mode, in addition to improving the layout of the traces or the influence of the process parameters of the printed circuit board, it can also improve resistance such as conductor film thickness tolerance, substrate film thickness tolerance, bonding contact impedance, and temperature rise. Signal distortion caused by other factors that cannot be resisted.

In summary, the terminal impedance adjustment method of the embodiment of the present invention analyzes the current value of the differential signal flowing through the terminal impedance to determine the feature point of the differential signal, and thereby determines the distortion state of the differential signal. Moreover, if it is determined that the differential signal is a distortion state such as amplification distortion or attenuation distortion, the signal waveform is brought to a corresponding limit. The value is calculated to adjust the impedance value of the terminal impedance. Thereby, the phenomenon that the characteristic impedance of the high-speed signal data transmission interface is discontinuous or mismatched due to factors such as the wiring, and the signal distortion caused by the distortion of the display screen can be improved. In addition, the embodiment of the present invention further proposes two adjustment flow modes, so as to perform automatic characteristic impedance matching adjustment in the initial stage of the receiver differential signal or signal transmission.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

S310~S370‧‧‧Steps

Claims (8)

A terminal impedance adjustment method is adapted to adjust a terminal impedance of a differential signal receiver, the terminal impedance adjustment method comprising: detecting, by a current detecting circuit, a current value of a differential signal flowing through the impedance of the terminal; The microcontroller determines a plurality of feature points of the differential signal according to the current value of the differential signal; and the microcontroller determines a distortion state of the differential signal according to the feature points; and the microcontroller controls the differential signal according to the differential signal The distortion state adjusts an impedance value of the terminal impedance. The terminal impedance adjustment method of claim 1, wherein the step of determining, by the microcontroller, the distortion state of the differential signal according to the feature points comprises: calculating a swing of the differential signal according to the feature points a voltage, a falling transient time, a level holding time, and a rising transient time; and determining the distortion state according to the swing voltage, the falling transient time, the level holding time, and the rising transient time. The terminal impedance adjustment method according to claim 2, wherein the swing voltage, the falling transient time, the level holding time, and the rising time of the differential signal are calculated by the microcontroller according to the feature points. The step of the state time further includes: counting, by using a clock counter, the temporally adjacent feature points of the feature points The time difference is obtained to obtain the falling transient time, the level holding time, and the rising transient time; and calculating, by the microcontroller, a voltage difference of the feature points of the feature points at the same time point to obtain the swing voltage. The terminal impedance adjustment method of claim 2, wherein the determining, by the microcontroller, the distortion state according to the swing voltage, the falling transient time, the level holding time, and the rising transient time further comprises: Comparing the swing voltage with a voltage threshold, comparing the falling transient time, the level holding time, and the rising transient time with a plurality of time thresholds; when the swing voltage is equal to the voltage threshold and the falling transient time When the level retention time and the rising transient time are equal to the time thresholds, the distortion state is a distortion-free state; when the swing voltage is less than the voltage threshold and the falling transient time and the rising transient time When the time threshold is less than the time threshold, the distortion state is a signal attenuation state; and when the swing voltage is greater than the voltage threshold and the falling transient time and the rising transient time are greater than the time thresholds, the distortion state Amplify the status for a signal. The terminal impedance adjustment method of claim 4, wherein the step of adjusting the impedance value of the terminal impedance according to the distortion state of the differential signal by the microcontroller further comprises: when the distortion state is the distortion-free state , the impedance value of the terminal impedance is not adjusted; When the distortion state is the signal attenuation state, the impedance value of the terminal impedance is raised; and when the distortion state is the signal amplification state, the impedance value of the terminal impedance is lowered. The terminal impedance adjustment method of claim 1, further comprising: detecting, by the current detecting circuit, the current value of the differential signal flowing through the terminal impedance when the differential signal receiver performs an initialization And when the differential signal receiver completes the initialization, controlling the current detecting circuit to stop detecting the current value of the differential signal flowing through the impedance of the terminal. The terminal impedance adjustment method of claim 2, further comprising: performing, during each detection period, detecting the current value of the differential signal flowing through the impedance of the terminal through the current detecting circuit. . The terminal impedance adjustment method according to claim 1, wherein the feature points are respectively a waveform turning point of the differential signal.