CMOS integrated circuit design (2): detailed interface circuit

First, CMOS integrated circuits drive other devices

1. CMOS-TTL integrated circuit interface

Since the low-level input current of TTL is 1.6mA, and the low-level output current of CMOS is only 1.5mA, an interface circuit is generally added. Here is an interface circuit that uses a single power supply. In FIG. 1, the function of the interface circuit is the CMOS integrated circuit buffer/level converter, which functions as a buffer drive or a logic level change, has a strong ability to sink current, and can directly drive TTL integration. The circuit is therefore easy to connect. However, you need to pay attention to the phase problem when using it. In the circuit, the CC4049 is a six-phase inverter/converter, and the CC4050 is a six-phase buffer/converter.

2. CMOS-HTL integrated circuit interface

The HTL integrated circuit is a standard industrial integrated circuit with high anti-interference performance. Since the CMOS integrated circuit has a wide operating voltage, it can share a +15V power supply with the HTL integrated circuit. At this time, the VOH, VOL, IIH, and IIL between the two are mutually satisfied, and it is not necessary to separately provide an interface circuit, and the connection circuit is directly connected. See FIG. 2 for the connection circuit.

3. CMOS-ECL integrated circuit interface

The ECL integrated circuit is an unsaturated digital logic circuit. Its working speed is the first of all logic circuits. The ECL is powered by a negative supply. The CMOS integrated circuit driving ECL integrated circuit can operate using a single power supply, as shown in FIG. The ECL integrated circuit is supplied with a -5.2V operating voltage, CMOS VDD is grounded, and VSS is connected to -5.2V. Taking the ECL integrated circuit CE10102 as an example, (CE10102 internally includes four 2-input NAND gates), the input high-level current IIH flowing into the ECL is 265uA, and the input high-level voltage VIH is -1.105V. The CMOS circuit is under a single power supply. Can meet the input needs of ECL integrated circuits.

4. CMOS-NMOS integrated circuit interface

The NMOS integrated circuit is an N-channel MOS circuit. The input impedance of the NMOS integrated circuit is high and basically does not need to sink current. Therefore, the CMOS and the NMOS integrated circuit do not have to consider the current load problem when connected.

Most NMOS integrated circuits are powered by a single set of positive power supplies, and are mostly 5V. The CMOS integrated circuit can be directly connected to the NMOS integrated circuit as long as it selects the same power source as the NMOS integrated circuit. However, when connecting directly from NMOS to CMOS, since the high level of the NMOS output is lower than the input high level of the CMOS integrated circuit, it is necessary to use a (potential) pull-up resistor R, as shown in Figure 4, the value of R Generally choose 2~100KΩ.