Rs-232 Communication Interface Chip In 0.6um Technology Design And Implementation,

Modern sensor device is developed facing the direction of intelligent and netlization. One of the key problems of the smart sensor device is the data communicating function. When the main sensor IC based on 0.6μm standard CMOS technology communicates with computer RS-232 series port, It is necessary to use monolithic RS-232 series IC to realize the exchange of the communication levels. If RS-232 communication circuit block can be integrated compatibly in sensor IC chip monolithically, it is possible to realize the smart sensor IC with data collecting function, analysis function and communicating function. To realize this idea, the first important research is to design a RS-232 communication circuit using 0.6μm standard CMOS technology.For the characteristics and performances that RS-232 transmitter/receiver should have, it is more suitable to be fabricated in 3μm CMOS or bipolar processes that have high voltage compression resistance (about 20V). Many structures of the circuit are not compatible with 0.6μm standard CMOS process. The biggest trouble is the voltage compression resistance problem of the devices, when we want to implement circuits which used to be designed in bigger-size processes. There is 20 volts voltage drop in RS-232 transmitter/receiver, and this value is far beyond the breakdown voltage of the gate oxide, which is only 10 volts. We must realize the RS-232 transmitter/receiver in Shanghua 0.6μm standard CMOS process by adjusting the circuit structures other than the process layers. The circuit is composed of two parts: inverting and non-inverting voltage doubler and transmitter. According to the RS-232C standards, the voltage doubler should supply DC voltages higher than ± 5V to the transmitter. The transmitter should transform data, as fast as 200kbps, from TTL/CMOS mode to EIA/TIA RS-232C mode. The slew rate should be higher than 30V/μs, and the delay time should be shorter than 1.5μs.In this research sensor IC I/O chip with RS-232 series driver/receiver function is designed and fabricated without any changes of 0.6μm standard CMOS process by reasonable adjusting the circuit configuration, the chip area is 4 mm~2. Voltage doubler supplies 7.6V non-inverting voltage and -5.6V inverting voltage to transmitter, when supplies by 5V DC voltage source. With 3KΩ resister and 1000pF capacitance loaded, the transmitter can transmit data as fast as 230.4kbps. The delay time and slew rate parameters are all fit or beyond the RS-232C standard. The circuit can replace some chips of a kind in some conditions. It costs less, and is smaller in size, easier to be realized in standard process, that is just what we want to get from modern electronicproducts. When integrated with sensors, it can help to communicate with PC terminals by changing the voltage mode, so that the entire system becomes a more intelligent one.