KR20080011851A - Switching circuit for uart/usb signal in mobile telecommunication terminal - Google Patents

Abstract

A UART(Universal Asynchronous Receiver/Transmitter)/USB(Universal Serial Bus) switching circuit of a mobile terminal is provided to prevent distortion of signals in supplying UART signal by including a Zener diode and the third transistor. A Zener diode(114) is provided at one side of the first signal path(BS_TX_DATA) to which a UART signal or a USB signal is inputted. The third transistor(113) receives voltage signals(Vg,Vs) via the Zener Diode(114) and the first signal path(BS_TX_DATA) and operates if a difference value(Vgs) between the voltage signals(Vg,Vs) is lower than a certain turn-on voltage. A USB transceiver operates selectively according to the supply of a voltage signal(Vbus) output from the third transistor. The first and second transistors(111,112) are selectively switched on or off according to the level of a signal inputted via the first signal path(BS_TX_DATA). A signal outputted through the ON/OFF operation of the first and second transistors(111,112) is transferred to an MSM(Mobile Station Modem) of a mobile terminal via a UART signal path.

Description

JRT / SWS switching circuit of mobile communication terminal {Switching circuit for UART / USB signal in mobile telecommunication terminal}

1 is a device configuration for implementing UART communication and USB communication between a mobile communication terminal and a computer according to the present invention.

2 is a circuit configuration diagram for switching the RXD signal of the UART and the Vbus signal of the USB input from the computer.

3 is a circuit configuration diagram for switching the TXD and CTS_N signals of the UART and the USB_D- and USB_D + signals of the USB.

4A and 4B show RXD signal waveforms when and without the third transistor, respectively;

The present invention relates to a UART / USB switching circuit of a mobile communication terminal, and more particularly, it is possible to efficiently perform data communication and simplify circuit configuration by enabling transmission and reception of UART signals and USB signals through a single circuit. The present invention relates to a UART / USB switching circuit of a mobile communication terminal.

Due to the development of the telecommunications industry and the rapid expansion of mobile communication services, many people are carrying mobile communication terminals, and multimedia functions such as playing music and video files in addition to mobile wireless telephony functions are common in response to various functions of users. Is being added.

As the mobile communication terminal is equipped with various additional functions including multimedia playback, the necessity of data communication with an external storage medium such as a personal computer is increasing. Data communication between a mobile terminal and a computer generally uses a universal asynchronous receiver / transmitter (hereinafter referred to as a 'UART') or a universal serial bus (hereinafter referred to as a 'USB'). It's done in a way.

A typical mobile communication terminal is provided with a port for UART communication and a port for USB communication to process data input through an RS-232C cable or a USB cable. Recently, an integrated cable, which is a combination of an RS-232C cable and a USB cable, has also been released.

Meanwhile, the UART communication signal and the USB communication signal are transmitted through different signal paths. Accordingly, a circuit for processing each data signal should be independently provided. As the circuits for processing the UART signal and the USB signal are separately provided in the mobile communication terminal, the circuit design becomes complicated and the number of pins included in the circuit increases.

The present invention has been made to solve the above problems, the mobile communication terminal that can efficiently perform data communication and simplify the circuit configuration by enabling the transmission and reception of UART signal and USB signal through a single circuit Its purpose is to provide a UART / USB switching circuit.

In order to achieve the above object, a UART / USB switching circuit of a mobile communication terminal according to the present invention is a state in which a mobile communication terminal and a computer are electrically connected to each other through an RS-232C cable and a USB cable. In the UART / USB switching circuit of a mobile communication terminal for switching a UART signal and a USB signal input to the mobile communication terminal through a cable, provided on one side of the first signal path (BA_TX_DATA) to which the UART signal or USB signal is input A third transistor that is operated only when the voltage signals Vg and Vs are received through the overvoltage blocking device, the overvoltage blocking device, and the first signal path, respectively, and the difference value Vgs of the corresponding voltage signal is less than or equal to a predetermined turn-on voltage. And a USB transceiver selectively operating according to the supply of the voltage signal Vbus output from the third transistor. It features.

Preferably, the apparatus further includes first and second transistors that are selectively turned on / off according to a level of a signal input through the first signal path, and on / off of the first and second transistors. The signal output through the off operation is transmitted to the MSM of the mobile communication terminal through the UART signal path.

Preferably, when the USB signal is input through the first signal path, the overvoltage blocking device outputs a reference voltage and the Vgs is smaller than the turn-on voltage of the third transistor so that the third transistor operates. Together, power is supplied to the USB transceiver.

Preferably, when a UART signal having a waveform of a high level and a low level is repeated through the first signal path, in the case of input of a high level UART signal, the overvoltage blocking device outputs a reference voltage. Since the Vgs is greater than the turn-on voltage of the third transistor so that the third transistor is not operated and no power is supplied to the USB transceiver, and in the case of input of a low level UART signal, the Vgs is the turn-on voltage of the third transistor. It becomes larger, and the 3rd transistor does not operate and power is not supplied to the USB transistor.

Advantageously, when a UART signal having a waveform of high and low levels is input through the first signal path, in the case of input of a high level UART signal, the first transistor is on and the first transistor is turned on. The two transistors are turned off to output a high level UART signal to the MSM. In the case of input of a low level UART signal, the first transistor is turned off and the second transistor is turned on to be low. Outputs the UART signal of the level to the MSM.

Preferably, the voltages of the UART signal and the USB signal are 3V and 5V, respectively, the reference voltage of the overvoltage blocking device is 2.4V, and the third transistor operates at -1.5V or less.

Preferably, the signal input through the first signal path is an RXD signal of a UART or a Vbus signal of a USB.

Preferably, the input and output terminals of the mobile communication terminal are further provided with a second and third signal paths, the second and third signal paths are shared by the UART signal and the USB signal, respectively, and the second and third The signal path is connected to the UART signal path and the USB signal path, respectively, via an analog switch, and the second and third signal paths are respectively connected to the UART signal path or the USB signal path according to the selective switching of the analog switch.

Preferably, the second signal path is connected to the TXD signal path of the UART and the USB_D- signal path of the USB via an analog switch, and the third signal path is connected to the CTS-N signal path of the UART via the analog switch. Connected to USB's USB_D + signal path.

Preferably, when power is supplied to the USB transceiver as the signal input through the first signal path is a USB signal, the second and third signal paths are respectively connected to the USB signal path by an operation of the analog switch. Is connected to transfer the USB signal to the USB transceiver, and if the signal input through the first signal path is a UART signal, the second and third signal paths are respectively connected to the UART signal path by an operation of the analog switch. Delivers a UART signal to the MSM.

According to a feature of the present invention, it is possible to efficiently switch the UART signal and the USB signal input and output from the mobile communication terminal using the voltage characteristics in the state connected via the mobile communication terminal, computer RS-232C cable and the USB cable. . Accordingly, the number of pins required for the input / output terminal of the mobile communication terminal can be significantly reduced, and the circuit configuration for the UART / USB can be simplified. In addition, since the zener diode and the third transistor are included in the switching circuit according to the present invention, signal distortion may be prevented when the UART signal is supplied.

Hereinafter, a UART / USB switching circuit of a mobile communication terminal according to the present invention will be described in detail with reference to the drawings. 1 is a device configuration for implementing UART communication and USB communication between a mobile communication terminal and a computer according to the present invention, Figure 2 is a circuit configuration for switching the RXD signal of the UART and the Vbus signal of the USB input from the computer 3 is a circuit configuration diagram for switching the TXD and CTS_N signals of the UART and the USB_D- and USB_D + signals of the USB.

First, as shown in FIG. 1, in order to implement UART communication and USB communication between a mobile communication terminal and a computer according to the present invention, the mobile communication terminal and the computer are basically connected by an RS-232C cable and a USB cable. The RS232C cable and the USB cable may be configured or integrally formed, and one side of the mobile communication terminal is provided with an input / output connector (I / O connector) to receive UART signals (RXD, TXD) from the RS-232C cable and the USB cable. , CTS_N) and USB signals (Vbus, USB_D-, USB_D +) or transmit data signals output from the mobile communication terminal to the RS-232C cable or USB cable.

The signal path input and output through the input / output connector is largely composed of a first signal path BA_TX_DATA 131, a second signal path BB_RX_DATA 131, and a third signal path CJ-READY 133. Various input / output signal paths provided in the connector other than the above path exist, but are not directly related to the present invention, and thus detailed description thereof will be omitted.

Each of the first, second and third signal paths 131, 132, 133 is shared by a UART signal and a USB signal. Specifically, the first signal path (BA_TX_DATA) 131 is a signal path of the RXD signal of the UART communication or the Vbus signal which is a power signal of the USB communication, the second signal path (BB_RX_DATA) 132 is the TXD of the UART communication The signal path is the signal path of the USB_D- signal of the USB communication, and the third signal path (CJ-READY) 133 is the signal path of the CTS_N signal of the UART communication and the USB_D + signal of the USB communication.

The UART signals (RXD, TXD, CTS_N) or USB signals (Vbus, USB_D-, USB_D +) received at the mobile communication terminal through the first to third signal paths 131, 132, 133 are connected to the mobile communication terminal. The UART signal or the USB signal may be transmitted to the computer through the first through the third paths.

Between the input and output connector and the MSM is a circuit for switching the UART signal and the USB signal, that is, the UART / USB switching circuit 100 according to the present invention is provided. The UART / USB switching circuit 100 switches the UART signal and the USB signal input from the connector and selectively transfers the UART signal to the MSM, which will be described later.

A USB transceiver is provided between the UART / USB switching circuit 100 and the MSM to transmit and receive a USB signal between the UART / USB switching circuit and the MSM. For reference, the UART signal is directly transmitted and received between the UART / USB switching circuit and the MSM without passing through a separate device such as the USB transceiver.

Now, the UART / USB switching circuit of the mobile communication terminal according to the present invention will be described in earnest.

First, as described above, the input / output connector inputs and outputs a UART signal (RXD, TXD, CTS_N) or a USB signal (Vbus, USB_D-, USB_D +) through a communication between a mobile communication terminal and a computer. Is input and output through three paths provided in the input / output connector, that is, the first, second, and third signal paths 131, 132, and 133, and RXD, Vbus, TXD, USB_D- and CTS_N and USB_D + signals are respectively passed through the second signal path BB_RX_DATA and the third signal path CJ_READY.

The UART / USB switching circuit 100 according to the present invention relates to a circuit for switching UART signals and USB signals inputted and outputted through the first to third signal paths, and specifically, the first signal path 131. And a switching circuit 110 for the signal passing through and a switching circuit 120 for the signal passing through the second and third signal paths 132 and 133. FIG. 2 is a circuit for switching the RXD signal of the UART communication and the Vbus signal of the USB communication inputted from the first signal path, and FIG. 3 shows the TXD, CTS_N signal of the UART communication and the USB_D-, USB_D + signals of the USB signal. Circuit.

First, referring to FIG. 2, when a predetermined signal transmitted from an RS-232C cable or a USB cable is input through the first signal path BA_TX_DATA 131, whether the corresponding signal is an RXD signal or a Vbus signal through the switching circuit of FIG. 2. It is determined whether or not it is determined and output to the corresponding path (RXD signal path or Vbus signal path).

Specifically, the switching circuit of FIG. 2 includes three transistors (first, second, and third transistors) 111, 112, 113, and one zener diode 114. The first and second transistors 111 and 112 are selectively turned on / off according to a level (high H or low L) of a signal input from the first signal path BA_TX_DATA. The three transistors 113 are set to operate only below a predetermined turn-on voltage, and the zener diode 114 serves to prevent output of a voltage above a predetermined reference voltage Vzd. Here, the first and second transistors 111 and 112 and the third transistor 113 should be composed of transistors of different types. For example, when the first and second transistors are npn type transistors, the third transistor should be a pnp type transistor. The Zener diode 114 may be a transient voltage suppressor (TVS).

The turn-on voltage of the third transistor 113 and the reference voltage Vzd of the zener diode 114 may be selectively applied in consideration of the voltage of the UART signal and the USB signal, the MSM receiving voltage, and the like. Considering that the voltage is 3V and the USB power signal is 5V, in one embodiment, the turn-on voltage of the third transistor 113 may be set to about −1.5V or less and the reference voltage Vzd of the zener diode 114 may be about 2.4V. have.

Looking at the operation of the switching circuit of Figure 2 having such a configuration as follows.

A predetermined signal is input through the first signal path BA_TX_DATA, and the case where the input signal is the RXD signal of the UART will be described first.

(1) When RXD signal of UART is input

The RXD signal of the UART has a high (H) level and a low (L) level. The high level voltage of the RXD signal of the UART becomes 3V as the UART signal is set to 3V. Accordingly, when a high level RXD signal is input through the first signal path, 2.4V is applied to the zener diode 114, and Vgs of the third transistor 113 is -0.6V (= 2.4V-3.0V). ) In order for the third transistor 113 to be turned on, Vgs must be smaller than -1.5V. In this case, since Vgs is -0.6V, the third transistor 113 is not operated. As a result, power is not supplied through the Vbus path of FIG. 2 so that the Vbus path and the USB transceiver are electrically open.

Following the high level RXD signal, when a low level RXD signal is input, 0 V is applied to the zener diode 114, and the Vgs of the third transistor 113 at this time becomes 0 V (= 0 V-0 V). Accordingly, the third transistor 113 is not operated and the Vbus and the USB transceiver are electrically disconnected as in the high level RXD signal input state.

Meanwhile, the high level RXD signal input to the first signal path is transmitted not only to the zener diode 114 but also to the first transistor 111. When the high level RXD signal is input, the first transistor ( 111 is on and the second transistor 112 is off. As a result, the high level RXD signal remains at the high level due to external pull up. On the other hand, when the low level RXD signal is input, the first transistor 111 is turned off and the second transistor 112 is turned on to output the corresponding RXD signal in a low level state. When the RXD signal input through the first signal path is input through this process, the disconnection state of the Vbus path and the USB transceiver is maintained so that the RXD signal can be stably output to the MSM without signal distortion of the RXD signal. 4A and 4B show an RXD signal waveform when the third transistor 113 is not applied and when the third transistor 113 is applied. It is understood that the RXD signal waveform can be stably maintained by applying the third transistor 113. Can be.

(2) When the Vbus signal of USB is input

A case in which a signal input through the first signal path 131 is a Vbus signal of USB is as follows. When the Vbus signal of the USB is input through the first signal path 131, the first transistor 111 is turned on and thus the second transistor 112 is turned off. Since the RXD signal is pulled up with a 2.8V, 10k resistor, the voltage is dropped by the 10k resistor, so that the voltage actually delivered to the MSM is 2.6V, thereby avoiding electrical damage to the MSM.

Meanwhile, the Vbus signal of the USB input through the first signal path is also transmitted to the zener diode 114. As the voltage of the Vbus signal is 5V, a voltage of 2.4V is applied to the zener diode 114. . At this time, the Vgs of the third transistor 113 becomes -2.6V (= 2.4V-5.0V) and satisfies the turn-on condition (-1.5V or less) of the third transistor 113 and as a result, the Vbus path The Vbus path and the USB transceiver are electrically shorted as they are powered on.

As described above, when (1) the RXD signal of the UART is input and (2) the Vbus signal of the USB is input, the RXD signal is stably switched by switching the RXD signal and the Vbus signal input to the first signal path. The signal is passed to the MSM and the Vbus power signal is sent to the USB transceiver, allowing each signal to be processed without distortion.

The switching circuit for the signal passing through the first signal path 131, that is, the RXD signal of the UART and the Vbus signal of the USB has been described. Hereinafter, the second and third signal paths 132 and 133 will be described. The switching circuit 120 for the signal passing through, that is, the TXD, CTS_N signal of the UART communication and the USB_D-, USB_D + signals of the USB signal will be described with reference to FIG. 3.

As shown in FIG. 3, a predetermined chip 121 having an analog switch (not shown) is provided, and the second signal path (BB_RX_DATA) 132 is TXD, USB_D− through the chip. The signal path and the third signal path (CJ_READY) 133 are connected to the CTS_N and USB_D + signal paths, respectively.

By the operation of the analog switch, the second signal path BB_RX_DATA may be selectively connected to the TXD signal path of the UART or the USB_D- signal path of the USB, and the third signal path CJ_READY is the CTS_N signal path of the UART or Can optionally be connected with USB's USB_D + signal path.

Meanwhile, a control pin USB_SEL is provided at one side of the chip 121 provided with the analog switch to selectively operate the analog switch according to a control signal transmitted from the control pin.

The control signal is determined according to the operating state of the switching circuit of FIG. 2. Specifically, when the signal input through the first signal path 131 of FIG. 2 is a Vbus power signal of USB, the Vbus signal path and the USB transceiver are short-circuited. In this case, a control signal is applied to the analog switch such that data should be inputted and outputted to the USB transceiver and the USB_D- and USB_D + signal paths are connected to the second and third signal paths 132 and 133, respectively. Should be. On the other hand, if the signal input through the first signal path 131 of FIG. 2 is the RXD signal of the UART, the analog switch such that the TXD and CTS_N signal paths are connected to the second and third signal paths 132 and 133, respectively. Corresponding control signal should be applied. As such a control signal, the MSM can grasp the operating state of the switching circuit of FIG. 2 and apply a corresponding control signal to the analog switch.

The UART / USB switching circuit of the mobile communication terminal according to the present invention has the following effects.

The UART signal and the USB signal input / output from the mobile communication terminal can be efficiently switched using the voltage characteristics while the mobile communication terminal, the computer RS-232C cable and the USB cable are connected. Accordingly, the number of pins required for the input / output terminal of the mobile communication terminal can be significantly reduced, and the circuit configuration for the UART / USB can be simplified. In addition, since the zener diode and the third transistor are included in the switching circuit according to the present invention, signal distortion may be prevented when the UART signal is supplied.

Claims (10)

In the state in which the mobile communication terminal and the computer are electrically connected through an RS-232C cable and a USB cable, the UART signal and the USB signal that are input to the mobile communication terminal through the RS-232C cable and the USB cable are switched. In UART / USB switching circuit, An overvoltage blocking device provided on one side of a first signal path BA_TX_DATA to which the UART signal or the USB signal is input; A third transistor receiving voltage signals Vg and Vs through the overvoltage blocking device and the first signal path, respectively, and operating only when a difference value Vgs of the corresponding voltage signal is equal to or less than a predetermined turn-on voltage; UART / USB switching circuit of a mobile communication terminal, characterized in that it comprises a USB transceiver that selectively operates in accordance with the supply of the voltage signal (Vbus) output from the third transistor. The method of claim 1, further comprising first and second transistors selectively on / off according to a level of a signal input through the first signal path. The UART / USB switching circuit of a mobile communication terminal, characterized in that the signal output through the on / off operation is transmitted to the MSM of the mobile communication terminal through the UART signal path. The method of claim 1, wherein when a USB signal is input through the first signal path, The overvoltage blocking device outputs a reference voltage, and the Vgs is smaller than the turn-on voltage of the third transistor, UART / USB switching circuit of a mobile communication terminal, characterized in that the power is supplied to the USB transceiver while the third transistor is operating. The UART signal of claim 1, wherein a UART signal having a waveform in which a high level and a low level are repeated through the first signal path is inputted. In the case of input of a high level UART signal, the overvoltage blocking device outputs a reference voltage and the Vgs is greater than the turn-on voltage of the third transistor so that the third transistor does not operate and power is supplied to the USB transceiver. Not, In the case of input of the low level UART signal, the Vgs is greater than the turn-on voltage of the third transistor, so that the third transistor does not operate and no power is supplied to the USB transistor. USB switching circuit. The UART signal of claim 1, wherein a UART signal having a waveform in which a high level and a low level are repeated through the first signal path is inputted. For input of a high level UART signal, the first transistor is on and the second transistor is off to output a high level UART signal to the MSM, In the case of input of the low level UART signal, the first transistor is turned off and the second transistor is turned on to output the low level UART signal to the MSM. USB switching circuit. The mobile communication apparatus of claim 1, wherein the voltages of the UART signal and the USB signal are 3V and 5V, respectively, the reference voltage of the overvoltage blocking device is 2.4V, and the third transistor operates at -1.5V or less. UART / USB switching circuit in the terminal. The UART / USB switching circuit of a mobile communication terminal according to claim 1, wherein the signal input through the first signal path is a RXD signal of a UART or a Vbus signal of a USB. The method of claim 1, wherein the input and output terminals of the mobile communication terminal is further provided with a second and third signal path, the second and third signal path is shared by the UART signal and USB signal, respectively, The second and third signal paths are connected to a UART signal path and a USB signal path, respectively, via an analog switch, and the second and third signal paths are respectively a UART signal path or a USB signal according to selective switching of the analog switch. UART / USB switching circuit of a mobile communication terminal, characterized in that connected to the path. The method of claim 8, wherein the second signal path is connected to the TXD signal path of the UART and the USB_D- signal path of the USB via an analog switch, The third signal path is connected to the CTS-N signal path of the UART and the USB_D + signal path of the USB via an analog switch UART / USB switching circuit of the mobile communication terminal. The method according to claim 1 or 8, When power is supplied to the USB transceiver as the signal input through the first signal path is a USB signal, the second and third signal paths are respectively connected to the USB signal path by the operation of the analog switch. Transmits a USB signal to the USB transceiver, If the signal input through the first signal path is a UART signal, the second and third signal paths are respectively connected to the UART signal path by the operation of the analog switch to transfer the UART signal to the MSM. UART / USB switching circuit of communication terminal.

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