1、 CMOS integrated circuit drives other devices
1. Interface of cmos-ttl IC
Because 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 usually needed. This paper introduces a single power interface circuit. In Figure 1, Gate II acts as an interface circuit. It is a CMOS integrated circuit buffer / level converter. It acts as a buffer driver or logic level converter. It has a strong ability to absorb current and can directly drive TTL integrated circuits. Therefore, it is easy to connect. However, we need to pay attention to the phase when using it. Cc4049 is a six phase buffer / converter, while cc4050 is a six phase buffer / converter.
2. Interface of cmos-htl IC
HTL IC is a standard industrial IC with high anti-interference performance. Because of its wide operating voltage, CMOS IC can share + 15V power supply with HTL IC. At this time, Voh, Vol, IIH and IIL between the two meet each other, so there is no need to set up another interface circuit, and they can be directly connected. See Figure 2 for the connection circuit.
3. Interface of cmos-ecl IC
ECL integrated circuit is an unsaturated digital logic circuit. Its working speed ranks first among all logic circuits. ECL adopts negative power supply. The ECL IC driven by CMOS IC can work with a single power supply, as shown in Fig. 3. ECL IC with – 5.2v working voltage, CMOS VDD grounded, VSS connected to – 5.2v. Taking ECL IC ce10102 as an example (ce10102 includes four 2-input or not gates), the input high-level current IIH flowing into ECL is 265ua, and the input high-level voltage VIH is -1.105v. Under a single power supply, the CMOS circuit can meet the input requirements of ECL IC.
4. Interface of cmos-nmos IC
NMOS integrated circuit is n-channel MOS circuit. The input impedance of NMOS integrated circuit is very high, and it does not need to absorb current basically. Therefore, the current load problem does not need to be considered when connecting CMOS and NMOS integrated circuit.
NMOS integrated circuits mostly use a single group of positive power supply, and more than 5V. CMOS IC can be directly connected with NMOS IC as long as the same power supply as NMOS IC is selected. However, when directly connecting from NMOS to CMOS, because the high level of NMOS output is lower than the high level of CMOS integrated circuit input, a (potential) pull-up resistor R is needed, as shown in Figure 4. The value of R is generally 2 ~ 100k Ω。
5. Interface of cmos-pmos IC
PMOS integrated circuit is a kind of device suitable for low speed and low frequency applications. PMOS integrated circuit is powered by – 24 V voltage. As shown in Figure 5, the cmos-pmos interface circuit uses two kinds of power supply. Using direct interface mode, general CMOS power supply voltage selection in 10 ~ 12V can meet the PMOS input level requirements.
6. Interface between CMOS and industrial control circuit
Industrial control circuit is a common circuit in industrial control system, which mostly uses 24 V working voltage. Fig. 6 shows a connection method between a CMOS circuit and an industrial control circuit. In the figure, R1 is the base bias resistance of the crystal triode vt. the function of VT is to pull the lower logic high level of the CMOS circuit to 24 V, so as to form a good connection between the two.
7. Interface of CMOS crystal triode vt
Fig. 7a is the interface of CMOS integrated circuit driving transistor. The crystal triode VT is connected in the form of common emitter, R1 is the load resistance of VT, R1 is the base bias resistance of VT, and the size of R1 is determined by the formula R1 = (voh-vbh) β/ IL decided. Where IL is the load current. VC should be selected according to VL and IL, and then IB (IB = IL) should be estimated/ β） Whether it is within the driving capacity of CMOS IC. If it exceeds, it can be replaced β A higher value transistor or Darlington transistor is shown in Fig. 7b. Vt of crystal triode is selected according to IL, IB = IL/（ β 1* β 2) The value of resistance R1 is: R1 = (Voh – 1.4) / (IB + 1.4 / r2), where R2 is introduced to improve the switching characteristics of the circuit, and its value is generally 4-10k Ω。
8. CMOS LED interface
Light emitting diode (LED) has many important characteristics, such as high reliability, low power consumption, long life and so on. It is one of the best terminal display devices used with CMOS integrated circuits. Led with high luminous efficiency can be directly driven by CMOS integrated circuit, especially when VDD = 10 ~ 18V, most of the LED can have enough brightness. It should be noted that the LED driven by CMOS integrated circuit should be connected in series with current limiting resistor, because when VDD = 10V, the output short-circuit current can reach about 20mA, if not properly protected by current limiting, the LED or CMOS integrated circuit will be easily damaged. Figure 8a is a CMOS integrated circuit that outputs a low-level led. The resistance R can be calculated by the formula: r = (vdd-vol-vled) / iled. Figure 8b shows a CMOS integrated circuit that outputs a high-level led. The value of resistance R is calculated by the formula r = (voh-vled) / iled. Where VLED and are the working voltage and current of LED respectively.
If the LED is driven by CMOS integrated circuit operating at low power supply voltage or by cooo series CMOS integrated circuit with poor load capacity, it may be difficult to make the LED emit enough bright light. The solution is to add a transistor driving circuit to get enough driving ability.
9. Interface between CMOS and SCR vs
Generally, the trigger current of medium and low power thyristors is less than 10mA, so most CMOS integrated circuits can directly drive thyristors. The specific circuit is shown in Figure 9. If more driving current is needed, it can be changed to CMOS buffer (e.g. cc4041) or buffer / driver (e.g. cc40107), or a crystal triode circuit can be added.