INTERFACE CIRCUIT
First Claim
1. An interface circuit for data communications, comprising:
- a USB interface circuit which interfaces with an external device via a communication cable by using a pair of terminals connected to the communication cable during USB communications;
a UART interface circuit which interfaces with another external device via the communication cable by using the pair of terminals connected to the communication cable during UART communications in common with the USB communications; and
a power source switching circuit which detects a power source voltage supplied from an external unit during the USB communications, and outputs either a USB power source voltage generated from the power source voltage or a voltage proportional to a core circuit power source voltage which is used during the UART communications to the USB interface circuit based on the detected result;
whereinthe USB interface circuit includes first and second switching circuits which connect the terminals during the USB communications, and a voltage from the power source switching circuit is input to the first and second switching circuits.
1 Assignment
0 Petitions
Accused Products
Abstract
An interface circuit is disclosed.
When a USB-BUS power source voltage VBUS is not normally supplied to the substrate gates of PMOS transistors of switches of a first switching circuit which controls connecting a terminal D+/RXD to a terminal D−/TXD in an HS driver circuit, and to the substrate gates of PMOS transistors of switches of a second switching circuit which controls connecting the terminal D+/RXD to the terminal D−/TXD in an FS driver circuit 6; an amplified core circuit power source voltage DVDD is supplied to the substrate gates of the PMOS transistors. When the USB-BUS power source voltage VBUS is normally supplied to the substrate gates of the PMOS transistors, a USB stabilized power source voltage VUSB is supplied to the substrate gates of the PMOS transistors.
-
Citations
6 Claims
-
1. An interface circuit for data communications, comprising:
-
a USB interface circuit which interfaces with an external device via a communication cable by using a pair of terminals connected to the communication cable during USB communications; a UART interface circuit which interfaces with another external device via the communication cable by using the pair of terminals connected to the communication cable during UART communications in common with the USB communications; and a power source switching circuit which detects a power source voltage supplied from an external unit during the USB communications, and outputs either a USB power source voltage generated from the power source voltage or a voltage proportional to a core circuit power source voltage which is used during the UART communications to the USB interface circuit based on the detected result;
whereinthe USB interface circuit includes first and second switching circuits which connect the terminals during the USB communications, and a voltage from the power source switching circuit is input to the first and second switching circuits. - View Dependent Claims (2, 3, 4, 5, 6)
-
Specification