USB chip and operation method thereof
A USB chip includes positive and negative data pins, first and second transceiver circuits, a switching circuit, and a control circuit. During a high-speed handshake stage, the control circuit controls the switching circuit to be in a second state to disconnect the positive and negative data pins from a first terminal impedance circuit and actuates the second transceiver circuit to transmit a second voltage signal via the positive and negative data pins alternately. During a high-speed transmission stage, the control circuit controls the switching circuit to be in a first state to connect the positive and negative data pins with the first terminal impedance circuit and actuates the first transceiver circuit to transmit a first voltage signal, which has a first voltage level lower than a voltage level of the second voltage signal, via the positive and negative data pins alternately.
1. A USB (universal serial bus) chip comprising:
a positive data pin;
a negative data pin;
a first transceiver circuit configured to transmit a first voltage signal via the positive data pin and the negative data pin alternately when the first transceiver circuit is actuated;
a second transceiver circuit configured to transmit a second voltage signal via the positive data pin and the negative data pin alternately when the second transceiver circuit is actuated, wherein a second voltage level of the second voltage signal is greater than a first voltage level of the first voltage signal;
a switching circuit configured to connect the positive data pin and the negative data pin with a first terminal impedance circuit in a first state and to disconnect the positive data pin and the negative data pin from the first terminal impedance circuit in a second state; and
a control circuit configured to
control the switching circuit to be in the second state during a high-speed handshake stage;
actuate the second transceiver circuit when the switching circuit is controlled to be in the second state;
control the switching circuit to be in the first state during a high-speed transmission stage; and
actuate the first transceiver circuit when the switching circuit is controlled to be in the first state.
2. The USB chip according to claim 1 , wherein the control circuit generates a switching stage signal so as to determine whether the control circuit is in the high-speed handshake stage or the high-speed transmission stage.
3. The USB chip according to claim 2 , wherein when a third voltage signal from a USB sub device exists at the negative data pin, the control circuit generates the switching stage signal indicating the high-speed handshake stage and operates in the high-speed handshake stage.
4. The USB chip according to claim 3 , wherein on the condition that a duration time of the third voltage signal is less than a time threshold, the control circuit further generates the switching stage signal indicating the high-speed handshake stage.
5. The USB chip according to claim 2 , wherein when a number of times of the second voltage signal being transmitted via the positive data pin is not less than a threshold of a number of times and the number of times of the second voltage signal being transmitted via the negative data pin is not less than the threshold of the number of times, the control circuit generates the switching stage signal indicating the high-speed transmission stage and operates in the high-speed transmission stage.
6. The USB chip according to claim 2 , further comprising a detection circuit connected to the control circuit, the positive data pin, and the negative date pin, wherein the detection circuit is configured to detect the second voltage level of the second voltage signal at the positive data pin and the second voltage level of the second voltage signal at the negative data pin; and
when the second voltage level is not greater than a voltage threshold, the control circuit generates the switching stage signal indicating the high-speed transmission stage and operates in the high-speed transmission stage.
7. The USB chip according to claim 6 , wherein the second voltage level of the second voltage signal at the positive data pin and the second voltage level of the second voltage signal at the negative data pin are pulled down to be not greater than the voltage threshold by a second terminal impedance circuit of a USB sub device.
8. The USB chip according to claim 1 , wherein the first transceiver circuit is a current-driven transceiver circuit, and the second transceiver circuit is a voltage-driven transceiver circuit.
9. The USB chip according to claim 1 , wherein when the switching circuit is controlled to be in the first state, the control circuit also disables the second transceiver circuit.
10. The USB chip according to claim 1 , wherein when the switching circuit is controlled to be in the second state, the control circuit also disables the first transceiver circuit.
11. The USB chip according to claim 1 , wherein the first terminal impedance circuit is inside the USB chip.
12. The USB chip according to claim 1 , wherein the first terminal impedance circuit is outside the USB chip, and the USB chip further comprises a connection end so as to be connected to the first terminal impedance circuit.
13. An operation method of a USB chip, wherein the USB chip comprises a positive data pin, a negative data pin, a first transceiver circuit, a second transceiver circuit, a switching circuit, and a control circuit; and the operation method comprises:
controlling, through the control circuit, the switching circuit to be in a second state during a high-speed handshake stage;
actuating the second transceiver circuit when the switching circuit is controlled to be in the second state;
controlling the switching circuit to be in a first state through the control circuit during a high-speed transmission stage; and
actuating the first transceiver circuit when the switching circuit is controlled to be in the first state;
wherein the switching circuit is configured to connect the positive data pin and the negative data pin with a first terminal impedance circuit in the first state and disconnect the positive data pin and the negative data pin from the first terminal impedance circuit in the second state;
when the first transceiver circuit is actuated, the first transceiver circuit alternately transmits a first voltage signal via the positive data pin and the negative data pin alternately; when the second transceiver circuit is actuated, the second transceiver circuit alternately transmits a second voltage signal via the positive data pin and the negative data pin alternately; and
wherein a second voltage level of the second voltage signal is greater than a first voltage level of the first voltage signal.
14. The operation method of a USB chip according to claim 13 , further comprising generating a switching stage signal through the control circuit so as to determine whether the control circuit is in the high-speed handshake stage or the high-speed transmission stage.
15. The operation method of a USB chip according to claim 14 , wherein the generating the switching stage signal through the control circuit comprises: when a third voltage signal from a USB sub device exists at the negative data pin, the control circuit generates the switching stage signal indicating the high-speed handshake stage and operating at the high-speed handshake stage.
16. The operation method of a USB chip according to claim 15 , wherein the switching stage signal indicating the high-speed handshake stage is further generated when a duration time of the third voltage signal is less than a time threshold.
17. The operation method of a USB chip according to claim 14 , wherein when a number of times of the second voltage signal being transmitted via the positive data pin is not less than a number of times threshold and the number of times of the second voltage signal being transmitted via the negative data pin is not less than the number of times threshold, the control circuit generates the switching stage signal indicating the high-speed transmission stage and operates in the high-speed transmission stage.
18. The operation method of a USB chip according to claim 14 , wherein the USB chip further comprises a detection circuit connected to the control circuit, and the detection circuit is configured to detect the second voltage level of the second voltage signal at the positive data pin and the second voltage level of the second voltage signal at the negative data pin; and
when the second voltage level is not greater than a voltage threshold, the control circuit generates the switching stage signal indicating the high-speed transmission stage and operates in the high-speed transmission stage.
19. The operation method of a USB chip according to claim 18 , wherein the second voltage level of the second voltage signal at the positive data pin and the second voltage level of the second voltage signal at the negative data pin are pulled down to be not greater than the voltage threshold by a second terminal impedance circuit of a USB sub device.
20. The operation method of a USB chip according to claim 13 , wherein the first transceiver circuit is a current-driven transceiver circuit, and the second transceiver circuit is a voltage-driven transceiver circuit.