Selection of electronic components: Eight principles for selecting semiconductor integrated circuits

admin September 28, 2023

Electronic components are the most basic components of electronic products. A large part of electronic equipment failures are caused by the performance, quality, or improper selection of components. Therefore, the correct selection of electronic components is a fundamental prerequisite for ensuring the reliability of electronic products. Reliability design is the process of selecting components that can still ensure high reliability in the worst-case usage environment.

Eight Principles for Selecting Semiconductor Integrated Circuits

1.The optimal order for integrated circuits is VLSI → Large scale integrated circuits → Medium scale integrated circuits → Small scale integrated circuits.

2. Try to use metal shell integrated circuits to facilitate heat dissipation

3. The selected integrated voltage regulator should have an internal overheat and overcurrent protection circuit.

4. The selection of ultra large scale integrated circuits should consider the possibility of circuit testing and screening, otherwise it will affect their reliability.

5. The selection of integrated circuit MOS devices should pay attention to the following:

1) The current load capacity of MOS devices is low, and capacitive and resistive loads can have a significant impact on the device's operating speed.

2) For sequential and combinational logic circuits, the highest frequency of the selected device should be 2-3 times higher than the applied part of the circuit.

3) The anti-interference of the input interface and device should be strong.

4) The driving ability of the device should be strong for the output interface.

6.When applying CMOS integrated circuits, the following issues should be noted:

1) The swing of the input voltage of CMOS integrated circuits should be controlled between the source power supply voltage and the drain power supply voltage.

2) The source supply voltage of CMOS integrated circuits, VSS, is low potential, while the drain supply voltage, VDD, is high potential and cannot be inverted. 3) When the input signal source and CMOS integrated circuit do not use the same set of power supplies, the CMOS integrated circuit power supply should be connected first, and then the communication signal source; The signal source should be disconnected first, and then the CMOS integrated circuit power supply should be disconnected.

4) If there are long wires or large integrating or filtering capacitors connected to the input (output) end of CMOS integrated circuits, a current limiting resistor (1-10k Ω) should be connected in series at the input (output) end to limit the input (output) current to within 10mA.

5) When the clock signal input to a CMOS integrated circuit causes slow edges due to overload or other reasons, it not only causes data errors, but also increases power consumption and decreases reliability. To improve the edge of the clock signal, a Schmidt trigger can be added to its input end.

7. All different input terminals in CMOS integrated circuits should not be idle, and according to their working functions, the following processing should generally be carried out:

1) The redundant terminals of AND and NOT gates should be connected to VDD or high level through a resistance of 0.5-1M Ω.

2) The redundant terminals of the OR gate and the NOR gate should be connected to the VSS or low level through a resistance of 0.5-1M Ω.

3) If the working speed of the circuit is not high and the power consumption is not particularly considered, multiple terminals can be connected in parallel with the same functional terminals on the same chip. It should be pointed out that there are some changes in transmission characteristics between parallel applications and individual applications.

8.When selecting integrated operational amplifiers and integrated comparators, the following issues should be noted:

1) When using negative feedback in integrated operational amplifiers without internal compensation, compensation measures should be taken to prevent self-excited oscillation.

2) When integrated comparators are used in open-loop applications, self-excited oscillations may sometimes occur. The main measures taken are to implement power decoupling and reduce wiring capacitance and inductance coupling.

3) When the output power is high, a buffer stage should be added. When connecting the output end directly to the outside of the circuit board, consideration should be given to adding short-circuit protection at the output end.

4) The input terminal should be protected against overvoltage, especially when the input terminal is connected directly to the outside of the circuit board, overvoltage protection measures must be taken at the input terminal.