CN102098035B - Analog switch control circuit and mobile phone - Google Patents

Abstract

The invention relates to the field of mobile terminals, and discloses an analog switch control circuit and a mobile phone. In the analog switch control circuit and the mobile phone provided by the present invention, since the second pin and the third pin of the MicroUSB interface are connected to the output end of the analog switch, the first pin is connected to the analog switch through a voltage divider circuit. The control terminal makes reasonable use of the power supply voltage of the USB cable and controls the analog switch by hardware. Compared with the conventional software control GPIO method, it is faster, simpler and more effective, and does not occupy GPIO port resources.

Description

An analog switch control circuit and mobile phone

technical field

The invention relates to the field of mobile terminals, in particular to an analog switch control circuit and a mobile phone.

Background technique

With the development of electronic technology and the continuous improvement of people's living standards, the use of various electronic devices is becoming more and more popular.

The analog switch is widely used in various electronic products. Multiple sets of mutually independent signal channels are used in one interface, and each set of signals can be flexibly converted according to the needs of users without mutual influence by switching the switch.

In the prior art, a general purpose input and output (GPIO) is generally controlled by software to switch channels of an analog switch. This control method is relatively simple and flexible, but it will cause some problems in some special occasions. For example, when an electronic device such as a mobile phone is turned off and connected to a host computer, software control is prone to errors.

Therefore, the prior art still needs to be improved and developed.

Contents of the invention

The technical problem to be solved by the present invention is to provide an analog switch control circuit and a mobile phone for the above-mentioned defects of the prior art, which can quickly control the analog switch for switching, and has a simple structure and is not easy to make mistakes.

The technical solution adopted by the present invention to solve technical problems is as follows:

An analog switch control circuit, comprising a Micro USB interface, and an analog switch communicated with the Micro USB interface, wherein the second pin and the third pin of the Micro USB interface are connected to the output end of the analog switch, and the Micro USB The first pin of the interface is connected to the control terminal of the analog switch through a voltage divider circuit.

The analog switch control circuit, wherein the voltage divider circuit includes a first resistor and a second resistor, one end of the first resistor is connected to the first pin of the Micro USB interface, and the other end of the first resistor is connected to the The control end of the analog switch, the other end of the first resistor is also connected to the reference ground through the second resistor.

The analog switch control circuit, wherein the analog switch is a single-pole double-throw analog switch, which is used to share two sets of mutually independent signal channels for one interface, and the single-pole double-throw analog switch includes a first pair of input terminals and The second pair of inputs.

In the analog switch control circuit, the resistance of the first resistor is 36K ohms, and the resistance of the second resistor is 24K ohms.

A mobile phone, comprising a mobile phone body, a circuit board arranged in the mobile phone body, and an analog switch control circuit arranged on the circuit board, wherein the analog switch control circuit includes a Micro USB interface, and an analog switch , the second pin and the third pin of the Micro USB interface are connected to the output end of the analog switch, and the first pin of the Micro USB interface is connected to the control end of the analog switch through a voltage divider circuit.

The mobile phone, wherein the voltage divider circuit includes a first resistor and a second resistor, one end of the first resistor is connected to the first pin of the Micro USB interface, and the other end of the first resistor is connected to the analog switch the control terminal of the first resistor, and the other terminal of the first resistor is also connected to the reference ground through the second resistor.

The mobile phone, wherein the analog switch is a single-pole double-throw analog switch, which is used to share two sets of mutually independent signal channels on one interface, and the single-pole double-throw analog switch includes a first pair of input terminals and a second pair of input.

The mobile phone, wherein a USB data transceiver circuit and a mobile phone application program download circuit are also arranged on the circuit board, and the mobile phone application program download circuit is connected to the first pair of input terminals of the single-pole double-throw analog switch, The USB data transceiving circuit is connected to the second pair of input terminals of the SPDT analog switch.

The mobile phone is characterized in that the resistance of the first resistor is 36K ohms, and the resistance of the second resistor is 24K ohms.

A kind of analog switch control circuit provided by the present invention and mobile phone, owing to adopt the 2nd pin of described Micro USB interface, the 3rd pin is connected with the output end of described analog switch, its 1st pin is connected to by a voltage divider circuit The control end of the analog switch rationally utilizes the power supply voltage carried by the USB line to control the analog switch in a hardware manner, which is faster, simpler and more effective than the conventional software control GPIO method, and does not occupy GPIO port resources.

Description of drawings

Figure 1 is a simplified diagram of the Micro USB interface and its analog switch circuit.

Figure 2 is a USB handshake timing diagram when the software GPIO controls the analog switch.

Fig. 3 is a diagram of an analog switch control circuit according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of the appearance and structure of the mobile phone according to the embodiment of the present invention.

Fig. 5 is a schematic diagram of the circuit structure of the mobile phone according to the embodiment of the present invention.

FIG. 6 is a timing diagram of USB handshake when the hardware circuit controls the analog switch according to the embodiment of the present invention.

Detailed ways

An analog switch control circuit and a mobile phone provided by the present invention, in order to make the purpose, technical solution and advantages of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Taking a MTK platform mobile phone with USB function as an example, the simplified diagram of the Micro USB interface and its analog switch circuit is shown in Figure 1. The analog switch in the figure is a single-pole double-throw analog switch 110, the power supply terminal VCC of the single-pole double-throw analog switch 110 is connected to the working power supply VBAT, and the GND terminal is connected to the reference ground. Micro USB (micro USB) interface 100 has gradually become an interface standard. Its 1-pin power supply and 5-pin ground are used as a charger or USB power charging interface, 2-pin and 3-pin are used as USB transmission signals, and 4-pin can be used for other purposes. .

And UART (program download line) is also a communication interface commonly used on mobile phones at present, such as the two-wire UART interface (UTXD and URXD signals in Figure 1), which can be mainly used to download applications on mobile phones. It can be seen that the signal pins on the Micro USB interface 100 are very limited, only 5. In order to save space and resources, a SPDT analog switch 110 is generally used, and the USB interface and UART interface on the main chip of the mobile phone are shared with pins 2 and 3 of a Micro USB interface.

The general program download cable does not have a power cord, but the USB cable has a power cord. In this way, the mobile phone can distinguish whether the USB cable or the program download cable is plugged in by detecting whether there is a high level on pin 1 of the Micro USB interface.

Usually the main chip of the mobile phone uses a general-purpose input and output signal (GPIO1 in Figure 1) to control the enable terminal (control terminal) of the analog switch to switch different signal channels. For example, as far as this mobile phone is concerned, the default initial state of the SPDT analog switch 110 is to connect channels B01 and B02 to D01 and D02 respectively, and to disconnect A01 and A02 from D01 and D02 respectively; The signal terminals D- and D+ of the interface are connected to the program download terminals UTXD and URXD.

When the GPIO1 output of the mobile phone main chip is at low level, the SPDT analog switch 110 also connects channels B01 and B02 to D01 and D02 respectively, and A01 and A02 are respectively disconnected from D01 and D02; and when the GPIO1 output of the mobile phone main chip When the level is high, the SPDT analog switch 110 is controlled to disconnect B01 and B02 from the D01 and D02 channels respectively, and A01 and A02 are respectively connected to the D01 and D02 channels.

Since the mobile phone is in an abnormal power-on state when using the UART interface to download the program, the main chip cannot control the GPIO signal, so the UART is generally connected to the signal channel of the default initial state of the single-pole double-throw analog switch 110, that is, connected to B01 and B02 mouth.

In this way, when the program download line (UART line) is inserted, pin 1 VCHG of the Micro USB interface 100 is at low level, and the single-pole double-throw analog switch 110 is connected to D01 and D02 by default, and the mobile phone can download the program normally.

Because the USB_DM and USB_DP of the USB function end are connected to A01 and A02 respectively. When the USB cable is plugged in, the mobile phone recognizes the high level of pin 1 of the Micro USB interface. When the mobile phone is turned on, it can switch the signal channel of the single-pole double-throw analog switch 110 to A01 and A02 to connect with D01 and D02 respectively by controlling GPIO1. , use the USB function now.

In practical applications, there will be a timing problem, which will cause the mobile phone to be incorrectly recognized as a USB device by the computer when it is turned off. By analyzing the protocol specifications of USB communication, we know the basic principle of USB host (such as computer) identifying peripherals. When the USB host detects the voltage difference on the signal lines D+ and D-, it will consider that there is a peripheral plugged in, start and The handshake program of the peripheral device sends a handshake signal every 500 milliseconds. If the peripheral device does not get a correct response three times in a row, the handshake timeout, and the host thinks that the inserted USB device is invalid. This process takes about 1500 milliseconds.

Let’s look at the mobile phone again. As shown in Figure 1, when the mobile phone is turned on, plug in the USB cable, and the mobile phone can immediately switch to high level by controlling GPIO1 after detecting the 5V voltage (VCHG) output from the host to the pin 1 of the USB interface. The SPDT analog switch 110 connects channels A01 and A02 to D01 and D02 respectively, so that the mobile phone and the host can normally shake hands within a time limit and use the USB function.

In the shutdown state, when the USB cable is plugged in, the signal sequence is shown in Figure 2. The mobile phone detects the 5V voltage (VCHG) on pin 1 of the USB interface and immediately turns on the power of each module. According to the UART communication protocol, the UTXD and URXD signals will output a set of high and low levels (as shown in the D+/UTXD line shown in Figure 2. Show). Since the B01 and B02 of the analog switch are connected to the D01 and D02 channels respectively in the default state, the D+ and D- levels are affected by the UTXD and URXD signals. After the host detects the pressure difference between D+ and D-, it thinks that there is a USB peripheral connected, and starts the handshake procedure. At this time, the mobile phone can only switch channels A01 and A02 of the analog switch to connect with D01 and D02 after completing the boot procedure and controlling GPIO1 to a high level (as shown in the GPIO1 line shown in Figure 2). At this time, the switching time of the analog switch About 2.3S, at this time, the host’s handshake procedure has timed out, and the computer cannot detect the mobile phone as a USB device.

Therefore, an analog switch control circuit 200 provided by the embodiment of the present invention, as shown in FIG. Independent signal channels share one interface. As shown in FIG. 3, the SPDT analog switch 220 includes a first pair of input terminals B1 and B2 and a second pair of input terminals A1 and A2. The first pair of input terminals B1 and B2 of the throw analog switch 220 are respectively connected to the mobile phone application program download terminals UTXD and URXD, and the second pair of input terminals A1 and A2 are respectively connected to the UBS data transceiver terminals USB_DP and USB_DM.

Wherein, the 2nd pin and the 3rd pin of the Micro USB interface 210 are connected with the output terminals D1 and D2 of the SPDT analog switch 220, and the 4th pin of the Micro USB interface 210 is used for other purposes. The fifth pin is connected to the reference ground, and the first pin of the Micro USB interface 210 is connected to the control terminals C1 and C2 of the SPDT analog switch 220 through a voltage divider circuit 230 .

Further, as shown in FIG. 3 , the voltage divider circuit 230 includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the first pin of the Micro USB interface 210, and one end of the first resistor R1 is connected to the first pin of the Micro USB interface 210. The other end is connected to the control terminals C1 and C2 of the SPDT analog switch 220 , and the other end of the first resistor R1 is also connected to the reference ground through the second resistor R2 . Preferably, the resistance of the first resistor is 36K ohms, and the resistance of the second resistor is 24K ohms.

It can be seen from the above that the analog switch control circuit 200 of the embodiment of the present invention is changed from the original software GPIO signal control to a hardware circuit (that is, the voltage divider circuit 230 shown in FIG. 3 ) to control the analog switch, which shortens the switching time of the analog switch. . As shown in FIG. 3 , the signal of GPIO1 is changed to the control signal (control level) of the voltage divider circuit 230 . The VCHG signal on pin 1 of the Micro USB interface 210 directly passes through a voltage divider circuit composed of R1 and R2 to obtain the control level required by the SPDT analog switch.

As shown in Figure 3, when a USB device is inserted into the Micro USB interface 210, the VCHG signal has a 5V level output by the host, and the voltage divider circuit 230 immediately enables the enabling terminal of the SPDT analog switch 220 (that is, the control terminal C1 and C2) signal is pulled high, the channel is switched to A1, A2 are respectively connected to D1, D2, D1, D2 are respectively disconnected from B1, B2 channel. It can quickly control the analog switch for switching, and has a simple structure and is not easy to make mistakes.

Based on the analog switch control circuit of the above-mentioned embodiment, the embodiment of the present invention also provides a mobile phone, as shown in Figure 4, comprising a mobile phone body 400, a circuit board 410 arranged in the mobile phone body 400, and a circuit board 410 arranged in the circuit The analog switch control circuit 200 on the board 410, as shown in Figure 5, wherein, the analog switch control circuit 200 includes a Micro USB interface 210, and a single pole double throw analog switch 220, for two groups of mutually independent signals The channels share one interface. As shown in FIG. 5 , the SPDT analog switch includes a first pair of input terminals B1 and B2 and a second pair of input terminals A1 and A2.

As shown in Figure 5, the second pin (D-) and the third pin (D+) of the Micro USB interface 210 are respectively connected to the output terminals D2 and D1 of the SPDT analog switch 220, and the Micro USB interface 210 The first pin is connected to the control terminals C1 and C2 of the SPDT analog switch 220 through a voltage divider circuit 230 .

Further, the voltage divider circuit 230 includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the first pin of the Micro USB interface 210, and the other end of the first resistor R1 is connected to the As for the control terminals C1 and C2 of the SPDT analog switch 220 , the other terminal of the first resistor R1 is also connected to the reference ground through the second resistor R2 . Preferably, the resistance of the first resistor R1 is 36K ohms, and the resistance of the second resistor R2 is 24K ohms.

Further, as shown in FIG. 5 , a USB data transceiver circuit 240 and a mobile phone application program download circuit 250 are also arranged on the circuit board 410, and the mobile phone application program download circuit 250 communicates with the mobile phone application program download circuit 250 through its UTXD terminal and URXD terminal respectively. The first pair of input terminals B1 and B2 of the SPDT analog switch 220 are connected, and the USB_DP terminal and USB_DM of the USB data transceiver circuit 240 are respectively connected to the second pair of input terminals A1 and A2 of the SPDT analog switch 220. connect.

As shown in FIG. 5 , when the mobile phone of the present invention is in a power-off state, the USB cable is inserted, and the signal sequence is shown in FIG. 6 . There is a 5V level output by the host on the VCHG signal, and the control signals of the control terminals C1 and C2 of the SPDT analog switch 220 (that is, the control level lines shown in Figure 6) are immediately pulled high through the voltage divider circuit 230, and the single-pole The channel switches A1 and A2 in the double-throw switch 220 are connected to D1 and D2 respectively, and the control D1 and D2 are disconnected from the channels B1 and B2 respectively. The levels on D+ and D- are not affected by the signals on UTXD and URXD, and the levels are all low until the mobile phone pulls up D+ (D+ line as shown in Figure 6), telling the host that there is a peripheral plugged in. The host starts the handshake program with the peripheral, uses the USB function, and correctly recognizes the mobile phone as a USB device.

It can be seen from the above that the mobile phone in the embodiment of the present invention rationally utilizes the power supply voltage carried by the USB line (that is, the voltage of the first pin of the Micro USB interface 210), and uses the hardware control method of the voltage divider circuit 230 to control the analog switch, which is more conventional. The method of controlling GPIO by software is faster, simpler and more effective, does not occupy GPIO port resources, and only adds very little hardware cost.

In summary, in the analog switch control circuit and the mobile phone provided by the present invention, since the second pin and the third pin of the Micro USB interface are connected to the output end of the analog switch, the first pin is passed through a The voltage divider circuit is connected to the control terminal of the analog switch, which reasonably utilizes the power supply voltage carried by the USB line to control the analog switch in a hardware manner, which is faster, simpler and more effective than the conventional software control GPIO method. Occupies GPIO port resources.

It should be understood that the application of the present invention is not limited to the above examples, and those skilled in the art can make improvements or transformations according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (5)

1. A kind of analog switch control circuit, comprise Micro USB interface, and the analog switch that communicates with Micro USB interface, it is characterized in that, the 2nd pin of Micro USB interface, the 3rd pin are connected with the output end of described analog switch, The first pin of the Micro USB interface is connected to the control terminal of the analog switch through a voltage divider circuit; The voltage divider circuit includes a first resistor and a second resistor, one end of the first resistor is connected to the first pin of the Micro USB interface, the other end of the first resistor is connected to the control terminal of the analog switch, and the first resistor The other end of the first resistor is also connected to the reference ground through the second resistor; The analog switch is a single-pole double-throw analog switch, which is used to share two sets of mutually independent signal channels to one interface, and the single-pole double-throw analog switch includes a first pair of input terminals and a second pair of input terminals. 2. The analog switch control circuit according to claim 1, wherein the resistance of the first resistor is 36K ohms, and the resistance of the second resistor is 24K ohms. 3. A mobile phone, comprising a mobile phone body, a circuit board arranged on the mobile phone body, and an analog switch control circuit arranged on the circuit board, wherein the analog switch control circuit comprises a Micro USB interface, And an analog switch, the second pin and the third pin of the Micro USB interface are connected to the output end of the analog switch, and the first pin of the Micro USB interface is connected to the control end of the analog switch through a voltage divider circuit; The voltage divider circuit includes a first resistor and a second resistor, one end of the first resistor is connected to the first pin of the Micro USB interface, the other end of the first resistor is connected to the control terminal of the analog switch, and the first resistor The other end of the first resistor is also connected to the reference ground through the second resistor; The analog switch is a single-pole double-throw analog switch, which is used to share two sets of mutually independent signal channels to one interface, and the single-pole double-throw analog switch includes a first pair of input terminals and a second pair of input terminals. 4. mobile phone according to claim 3, is characterized in that, on described circuit board, also be provided with USB data transceiver circuit and mobile phone application program download circuit, described mobile phone application program download circuit and described SPDT analog switch The first pair of input terminals of the USB data transceiver circuit is connected with the second pair of input terminals of the single-pole double-throw analog switch. 5. The mobile phone according to claim 3 or 4, wherein the resistance of the first resistor is 36K ohms, and the resistance of the second resistor is 24K ohms.

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