TW565995B - Transmitter for outputting differential signals of different voltage levels - Google Patents

Abstract

A differential signal transmitter including a driver circuit that generates a differential signal in response to data input. The amplitude of the voltage swings in the differential circuit is controlled by an electrical bias. Two data inputs, one being the original Data and the other being Data bar, are connected to the transistors and cause the required current swings. The transmitter further includes a control circuit with an input for a single-bit control line for adjusting the bias to produce different swing amplitudes according to a control indicator inputted from the control line. The control circuit inputs one or more current sources and outputs the sum of one or more of the current sources according to the control indicator and the outputted current is used as the electrical bias.

Description

565995 V. Description of the invention α) Field of the invention The present invention provides a differential signal transmitter, especially a low-power differential signal transmitter that can output differential signals with different voltage levels. Background of the invention

Swing differential signaling is a low-power technology used in data transmission systems. Because of its low power consumption, low electromagnetic radiation, high signal / noise ratio, and high data transmission rate, low power differential signals are widely used in data transmission systems. The swing amplitude (or peak-to-trough amplitude) of the differential signal in current differential signal systems varies with the type of system, but is usually less than 600 millivolts.

Please refer to Fig. 1. Fig. 1 is a simple circuit diagram of a conventional differential signal transmitter 10. The differential signal transmitter 10 includes a bias voltage 12, two current sources 1 4 and 1 6, a ground point 3 2, two normal phase transistors 2 4 and 2 6, two reverse phase transistors 2 0 and 2 2, and A resistor 18 (R 2) and a bias voltage 12 control the operation of the current sources 14 and 16. The differential signal transmitter 10 further includes two input terminals, which are respectively used to input a normal phase data and an inverse data relative to the normal phase data. The bias source 12 controls the current input from the current source 14 to the inverting transistor 20 or 22 to be within a predetermined range. When the normal phase data is a high logic signal

Page 5 565995 V. Description of the invention (2) (10 gichigh) (At the same time, the inverted data is a low logic signal), the transistors 2 4 and 22 will be turned on to make the current source 1 4 The flowing electricity and current can flow to node B, and the current flowing from node B will flow to resistor 18, and the current flowing from resistor 18 will first flow to node A and then through the conducting transistor 2 4 And the current source 16 and finally flow to the ground point 3 2. The voltages at node B and node A are VoutP and VoutN, respectively. When the normal phase data is a low logic signal (at the same time, the reverse phase data is a high logic signal), the transistors 20 and 26 will be turned on, so that the current from the current source 14 can flow. Node A, and the current flowing from node A will flow to resistor 18, and the current flowing from resistor 18 will first flow to Lang point B, and then pass through the transistor 2 6 and current source 16, and finally flow To ground point 3 2. When the normal phase data is a high logic signal, the output signal of the differential signal transmitter 10 is VoutP minus VoutN, which will be equal to the current I flowing through the resistance 18 times the resistance value R2 of the resistance 18, also That is, VoutP-VoutN = I * R2, and the output signal at this time corresponds to the logic π Γ of the differential signal. When the normal phase data is a low logic signal, the output signal of the differential signal transmitter 10 is VoutP minus VoutN, which is equal to-I * R2, which corresponds to the logic of the differential signal currently on the market. There are three types of differential signals most commonly used. The first type is Low Voltage Differential Signaling (LVDS). Its voltage level ranges from 24 7 mV to 45 4 mV. The voltage level of the more typical LVDS is 350 millivolts. The second type of differential signal is a mini low voltage differential signal.

565995 V. Invention Description (3) (Mini-LVDS), the voltage level of which ranges from 300 millivolts to 600 millivolts, while the voltage level of the more typical Mini-LVDS is 450 millivolts Volt. The last type of differential signal is Reduced Swing Differential Signaling (RSDSTM). Its voltage level ranges from 100 millivolts to 400 millivolts, which is more typical. The RSDSTk voltage bit criterion is 200 millivolts. The purpose of the differential signal transmitter 10 is to be able to change the voltage level amplitude of the differential signal in a same system to meet the needs of different devices in the system. And what kind of differential signal transmitter 10 should be configured in this system involves a lot of design considerations, such as the frequency rabbit required for the system's signal application, the length of the connecting wire in the system, and the drive circuit in the system The transition time, and the quality of the signal in the system. These considerations will vary to varying degrees due to different system characteristics, so compatibility between different systems is very small. In this way, when designing the differential signal transmitter 10 in different application areas, the system designer will face the sacrifice of efficiency in order to reduce costs, or increase the voltage amplitude of the differential signal transmitter 10 in order to improve efficiency. The dilemma. OBJECTS AND SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a differential signal transmitter which can be more effectively applied to systems with different differential voltage ranges to solve the above problems. ~

Page 7 565995 V. Description of the invention (4) The present invention provides a differential signal transmitter which includes a driving circuit and a current bias control circuit. The driving circuit generates a differential signal according to the input data, and the voltage level of the differential signal is controlled by the current bias control circuit. The current bias control circuit includes an input terminal for receiving a control signal. The current bias control circuit can obtain wheel bias currents of different sizes according to the input system signal. The circuit can output the signal. The current of the bias-biasing signal is low power, which is the control output of the drive control. The power is controlled by the output or both are used as input control. For example, the control is a first voltage. The differential signal transmitter described above. The current biases two or more current sources, and according to one or more, the current output from the sum of the one or more current sources from the outlet of the second wheel is used as the drive. ‘= ;, if the control signal is a high-voltage circuit, the current is one first two = accurate, then

Ϊ] Ϊ level, the current bias control circuit: J pre-threshold value. Regardless of whether the control signal is high voltage f, the bias voltage input from the current bias control circuit is used. The detailed description of the scared current t is detailed in May with reference to FIG. 2. FIG. 2 is a circuit diagram of the present invention. The moving signal transmitter includes a simple driving circuit 50, and the moving circuit 50 includes two control circuits 52. And shaking source 5 4 and 5 6, one ground

565995 V. Description of the invention (5) Point 7 2. Two normal phase transistors 6 4 and 6 6, two reverse phase transistors 6 0 and 6 2, and a resistor 58 (R2). The driving circuit 50 further includes two input terminals, which are respectively used for inputting a normal phase data and an inverted phase data relative to the normal phase data. The operating principle and procedures of the driving device 50 are all known technologies, and are similar to the aforementioned known technologies. The current output from the bias control current source 5 4 output from the current bias control circuit 5 2 to the inverter transistor 60 or 62 is within a predetermined range. When the normal phase data is a high logic signal (10 gichi gh) (at the same time, the reverse phase data is a low logic signal), the transistors 6 4 and 6 2 will be turned on to make the current source 5 4 The flowing current can flow to node B, and the current flowing from node B will flow to resistor 58, and the current flowing from resistor 58 will flow to node A first, and then pass through the transistor 64 and the current source. 5 6. Finally flow to the ground point 72. The voltages at node B and node A are VoutP and VoutN, respectively. When the normal phase data is a low logic signal (at the same time, the reverse phase data is a high logic signal), the transistors 60 and 66 will be turned on, so that the current flowing from the current source 54 can flow. Node A, and the current flowing from node A will flow to resistor 5 8 and the current flowing from resistor 5 8 will first flow to node B, and then pass through the transistor 6 6 and current source 5 6 and finally to Ground point 7 2. When the normal phase data is a high logic signal, the output signal of the differential signal transmitter is V 〇ut P minus V 〇ut N, which is equal to the current I flowing through the resistor 5 8 times the resistance of the resistance 58 The value R2, that is, VoutP-VoutN = I * R2, and the output signal at this time corresponds to the logic π 1π of the differential signal. When the normal phase data is a low logic signal, the output signal of the differential signal transmitter 10

565995 V. Description of the invention (6) It is said that VoutP minus VoutN, which is equal to ~ 丨 * ", which corresponds to the logic of the differential signal" 〇 ". Refer to Figure 3 'Figure 3 is the differential signal of the invention A simple circuit diagram of a current bias control circuit 80 in a transmitter. Obviously, there are quite a few types of current bias control circuits 80, and the current bias control circuit 80 shown in FIG. 3 is only a large number of current biases. A type of control circuit. The design concept of the present invention can be applied to any method using one or more control signals to control one or more current sources accordingly, wherein the current source is used as a bias voltage for the difference transmitter. The bias control circuit 80 includes two normal-phase transistors 9 2 and 9 4, five-phase inverters 82, 84, 86, 88, and 90, three current sources h, ι2, and 13, a ground point 96, and An electrical bias PBI AS. In this example, the ground point 96 is used as the bias of the driving circuit 50. The current bias control circuit 80 also includes four input terminals a, B, C, and D, respectively Used to receive control signals to control the output to the ground point 9 6 Current. Obviously, 'a single control signal is sufficient to control the current output to the ground point 9 6'. The present invention is not limited to the number of control signals. In this example, four control signals are used for convenience of explanation. The present invention is very suitable for differential signal systems with different requirements. The current bias control circuit 80 operates according to the control of the input signal. For example, if the current bias control circuit 80 receives the control signal

565995 V. Description of the invention (7) A, B, C, and D are sequentially 0, bu, and 0. Correspondingly, transistors 8 8 and 9 2 will be turned on, and transistors 90 and 9 4 are Will not conduct. In this way, the current flowing to the ground point 96 will be equal to 11 + I 2. For another example, if the control signals a, b, C, and D received by the current bias control circuit 80 are 1, 0, 0, and 1, in order, correspondingly, the transistors 88 and 92 are not Will turn on, and transistors 90 and 94 will turn on. As a result, the current flowing to the ground point 96 will be equal to Π + I 3. Obviously, the current flowing to the ground point 96 will change with different combinations of control signals. By appropriately selecting the combination of the current sources 11, I2, and I3, for example, the sum of one or more currents can be used as the bias voltage of the driving circuit 50, so that the driving circuit 50 can be generated within a predetermined voltage level range. Differential signal. The predetermined voltage level range can be modified to different degrees by changing the combination of the control signals A, B, C, and D. For example, the sum of the current sources I 1 and I 2 (as shown in the first example) can generate an LVDS differential signal with a voltage level range between 247-454 millivolts. In the second example, the control signals A, B, C, and D are set to (1, 0, 0, 1) respectively. In this way, the current flowing through the ground point 96 is equal to the current sources 11 and I The sum of 3 ', therefore, the driving circuit 50 generates a Mini-LVDS differential signal, and its voltage level ranges from 230 to 600 millivolts. Of course, other combinations of control signals can also be used to generate RSDSTM differential signals with voltage levels ranging from 100 to 400 millivolts. Compared with the conventional technology, the advantage of the driving circuit 50 of the present invention is that ’

565995 V. Description of the invention (8) By using a current bias control circuit and different combinations of control signals in a single differential signal transmitter, biases of different levels required by the driving circuit can be generated. This technology using only a single differential signal transmitter can generate differential signals such as LVDS, Mini-LVDS, and RSDST (R). It can also easily generate other differential signals with different voltage levels. Moreover, compared with the prior art, which requires more than one differential signal transmitter to generate differential signals with different voltage level ranges, the driving circuit 50 of the present invention has low power consumption, low electromagnetic radiation, and high signal / noise. Characteristics such as signal-to-noise ratio (SNR) and high data transmission rate, and the invention also solves the compatibility problem that cannot be solved by the prior art. The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application for the present invention shall fall within the scope of the invention patent.

Page 12 565995 Simple illustration of the diagram Simple illustration of the diagram Figure 1 is a simple circuit diagram of a conventional differential signal transmitter. FIG. 2 is a simple circuit diagram of a differential signal transmitter according to the present invention. Fig. 3 is a simple circuit diagram of a current bias control circuit in the differential signal transmitter of the present invention shown in Fig. 2. Explanation of symbols of the drawing 10 Differential signal transmitter 12 Bias 14, 16 Current source 18> 58 Resistor 20> 11, 60 ^ 62 '82> 84, 86 ^ 88 ^ 90 Inverter transistor 24> 26 ~ 6 6 '92 ^ 94 Normal Phase Transistor 50 Drive Circuit 52 > 80 Current Bias Control Circuit 54 ^ 56 Current Source 32 > Ί2, 96 Ground Point

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Claims (1)

565995 VI. Scope of patent application 1. A differential signal transmitter, which includes a driving circuit, is used to generate a differential signal depending on the voltage level of the differential signal. -Current bias control circuit; to receive a first control signal, the current bias ^ an input 1 is used to connect the signal output with the value of the bias; the control circuit can be based on the -control 2 _ As described in item 1 of the scope of patent application, the control signal has only a single bit. Differential signal transmitter 4 · The differential signal transmitter as described in item 3 of the patent claim, wherein when the current bias control circuit outputs a current having a first current value as the bias of the drive circuit, the drive circuit A low voltage differential signal (LVDS) is generated according to the bias voltage. 5 · The differential signal transmitter as described in claim 3 of the patent scope, wherein when the current bias control circuit outputs a current having a second current value as the bias of the drive circuit, the drive The circuit is based on the bias voltage to generate a your-LVDS (Mini-LVDS) differential signal. 565995 6. Scope of patent application 6. The differential signal transmitter as described in item 3 of the scope of patent application, wherein when the current bias control circuit outputs a voltage with a third current value as the bias of the driving circuit When the voltage is applied, the driving circuit generates a Reduced Swing Differential Signaling (RSDSTM) based on the bias voltage. 7. The differential signal transmitter according to item 1 of the scope of patent application, wherein when the current bias control circuit outputs a current having a predetermined current value as the bias of the driving circuit, the device having the first The current of the predetermined current value is the sum of at least one current source, and the current bias control circuit selects different combinations of current sources from the at least one current source according to the first control signal as the first predetermined current source. The current value of the current. 8. The differential signal transmitter according to item 1 of the scope of patent application, wherein the current bias control circuit further includes a second input terminal for receiving a second control signal. 9. A method for transmitting a differential signal from a transmitter, the transmitter includes a driving circuit and a current bias control circuit, the driving circuit can generate the differential signal according to the input data, and the differential signal The value is controlled by a bias voltage. The method includes: receiving a first control signal from a first input terminal of the current bias control circuit; and generating the current bias control circuit according to the first control signal. 565995 VI. Scope of patent application Bias voltage at the same level; and Generate the differential signal according to the bias voltage with different levels. 10. The method as described in item 9 of the scope of patent application, further comprising the driving circuit generating an LVDS according to the bias voltage when the current bias control circuit outputs a bias voltage having a first predetermined level. Differential signal. 1 1. The method according to item 9 of the patent application scope, further comprising the driving circuit generating a Mini- based on the bias when the current bias control circuit outputs a bias having a second predetermined level. LVD S differential signal. 1 2. The method according to item 9 of the scope of patent application, further comprising the driving circuit generating an RSDS TM according to the bias when the current bias control circuit outputs a bias having a third predetermined level. Differential signal. Page 16