This application claims the benefit of Korean Patent Application No. 98-45734, filed Oct. 29, 1998, the disclosure of which is hereby incorporated herein by reference.
The present invention relates to signal transmission in general, and more particularly, to signal transmission between integrated circuit devices.
Many techniques have been developed to reduce the amount of noise introduced into data transmitted between integrated circuit (IC) devices. Two such data transmission techniques include single-ended interfaces and differential interfaces.
Referring to FIG. 1, a conventional single-ended interface can include integrated circuit devices 101 and 121 and a transmission line 111 therebetween. The integrated circuit device 101 includes a driver 103 and a pad 105, and the integrated circuit device 121 includes a receiver 123 and a pad 125. The transmission line 111 is connected between the pads 105 and 125. The driver 103 compares input data S1 to a reference voltage Vref, generates a high or low level signal, and transmits the signal on the transmission line 111. The signal is transferred to the receiver 123 via the transmission line 111. The receiver 123 compares the signal transferred via the transmission line 111 to the reference voltage Vref, and produces the data S1. Unfortunately, the integrity of data transferred using single-ended interfaces may be adversely affected by the presence of common mode noise, such as echo or ground bounce.
Referring to FIG. 2, a differential interface can include integrated circuit devices 201 and 221 and transmission lines 211 and 213 therebetween. The integrated circuit device 201 includes drivers 203 and 205 and pads 207 and 209. The integrated circuit device 221 includes a receiver 223 and pads 225 and 227. The transmission lines 211 and 213 electrically couple the pad 207 to the pad 225 and the pad 209 to the pad 227 respectively. The driver 203 amplifies input data S1 and transmits the input data on the transmission line 211, and the driver 205 amplifies an inverted signal S1B of the input data S1 and transmits the inverted signal on the transmission line 213. The data S1 and S1B are input to the receiver 223 via the transmission lines 211 and 213, respectively. The receiver 223 compares the signals S1 and S1B transmitted via the transmission lines 211 and 213, and produces the data S1. Unfortunately, the data integrity of a signal transmitted using a differential method may be adversely affected by common mode noise. In addition, the use of a differential interface may complicate the structure of the interface, thereby possibly increasing the cost of manufacturing the interface.
It is, therefore, an object of the present invention to allow improvement in the transmission of signals between integrated circuit devices.
It is another object of the present invention to allow improved noise immunity for signals transmitted between integrated circuit devices.
It is another object of the present invention to allow reductions in cost of interfaces used to transmit signals between integrated circuits.
These, and other objects may be provided by a transmission circuit that includes a first driver circuit that generates a first transmit signal in response to first and second input signals, the first transmit signal being transmitted from the integrated circuit device. A second driver circuit generates a second transmit signal in response to the first transmit signal and a third input signal, the second transmit signal being transmitted from the integrated circuit device. Accordingly, the likelihood of data loss can be reduced despite the presence of common mode noise. The use of one transmission line per receiver may also simplify the structure of an embodiment according to the present invention.
In a further aspect of the present invention, a first pad is electrically coupled to the first driver circuit and a second pad is electrically coupled to the second driver circuit.
In another aspect of the present invention, a pad is electrically coupled to the first input signal, wherein the first input signal is transmitted from the integrated circuit device.
In still another aspect of the present invention, a first detector circuit is electrically coupled to the first and second input signals and detects when the first and second input signals are a high logic level. A second detector circuit is electrically coupled to the first and second input signals and detects when the first and second input signals are a low logic level. A transmit signal generator is electrically coupled to the first and second detectors and generates the first transmit signal at a first voltage level when at least one of the first and second detector circuits detects that the first and second input signals are both a high logic level and that generates the first transmit signal at a second voltage level when at least one of the first and second detector circuits detects that the first and second input signals are both a low logic level.