Do you really know how to select capacitors? The following are key points of capacitor selection
Issuing time:2021-11-01 16:29
Four important indicators of capacitor selection:
(1) Capacity: the capacity of the capacitor, that is, the capacity of storing charge. The basic unit of capacity is Farad (F), but on the motherboard we are common micro method (μF), skin method (pF) and other units (conversion relationship is 1 Farad =1000000 micro method, 1 micro method =1000 na =1000000 skin method). The capacity is directly marked, such as GSC4700μF, generally speaking, the larger the better.
(2) Voltage withstand value: it refers to the maximum DC voltage or maximum EFFECTIVE VALUE of AC voltage that the capacitor can work reliably for a long time within the rated temperature range. Different capacitors have different withstand values, mostly between 6.3V and 16V.
(4) Other indicators: Some capacitors also have a golden ribbon line, printed with a large hollow "I" letter, it indicates that the capacitor is a LOWESR low loss capacitor. Some capacitors will also be marked with ESR (equivalent resistance) value, the lower the ESR, the smaller the loss, the greater the output current, low ESR capacitor quality is good.
Rules for capacitor selection:
Jie aluminum electrolytic capacitor selection rules
1, in general application, choose standard type, life 1000HR~3000HR (for price consideration, carefully choose long life type), choose aluminum electrolytic capacitor life as far as possible choose 2000Hr.
2, for the aluminum electrolytic capacitor voltage, 3.3V system take 10V, 5V system take 10V, 12V system take 25V, 24V system take 50V; For a system larger than 48V, select 100V.
3, aluminum electrolytic capacitor must be selected at 105 degrees.
4. For the capacitance value of aluminum electrolytic capacitor, series 10, 22, 47 are preferred; Under 25V, capacitive models such as 224, 105 and 475 are prohibited (replaced by lamellar multilayer ceramic capacitors or tantalum electrolytic capacitors).
5, for high voltage aluminum electrolytic capacitor to retain 400V. Non - polar aluminum electrolytic capacitor is prohibited.
6, ordinary aluminum electrolytic capacitor selection brand "SAMWHA" (sanhe), high-end aluminum electrolytic capacitor selection NCC (black gold just) or other Japanese famous aluminum electrolytic capacitor.
7, prohibit the use of aluminum electrolytic capacitor chip.
Rule of selection for Tantalum electrolytic capacitor
1. Tantalum electrolytic capacitors with a voltage withstand of more than 35V are prohibited.
2. Pin type tantalum electrolytic capacitors are forbidden.
3. For the voltage withstand of tantalum electrolytic capacitors, 10V for 3.3V system, 16V for 5V system, and 35V for 12V system; 10V, 16V, and 35V are preferred; 4V, 6.3V, and 50V are forbidden (aluminum electrolytic capacitors are used instead).
4. Capacitance of tantalum electrolytic capacitors: 10, 22, 47 series are preferred. The tantalum electrolytic capacitors with capacitance below 105 are forbidden (replaced by ceramic capacitors).
5, tantalum electrolytic capacitor brand: KEMET, AVX.
➂ Plate multilayer ceramic capacitor selection rules
1, high Q ceramic capacitor carefully selected; Only on rf circuits.
2, flake multilayer ceramic capacitor packaging: 0603, 0805 preferred, 1206, 1210 carefully, above 1808 forbidden.
3, chip multilayer ceramic capacitance voltage: preferably 25V, 50V, 100V; The capacity above 106 is not more than 25V.
4. Capacitive capacity of flake multilayer ceramics: 10, 22, 33, 47, 68 series are preferred.
5, flake multilayer ceramic capacitor materials, preferably NPO, X7R, X5R, other forbidden.
6, flake multilayer ceramic capacitor brand: TAIYO, MURATA, KEMET, TEMEX (high Q ceramic capacitor).
Coil current: 25 ohm
1. It is forbidden to use such capacitors for new products (use flake multilayer ceramic capacitors instead).
How to select motherboard capacitance?
1, look at the brand:
Motherboard capacitors are mainly divided into Taiwan and Japanese, Japanese brands are: NICHICON, RUBICON, RUBYCON (Ruby), KZG, SANYO (SANYO), PANASONIC (PANASONIC), NIPPON, FUJITSU (FUJITSU), etc. Taiwan brands: TAICON, G-Luxcon, TeaosEN, CAPXON, OST, GSC, RLS and so on.
Generally speaking, the performance of Japanese capacitor is better, in terms of voltage resistance, temperature resistance, service life and other aspects than Taiwan capacitor is excellent, early capacitor "pulp explosion" event, also did not happen in the Japanese capacitor, so if you want to choose a piece of overfrequency, stability and motherboard, may wish to see the capacitor on the motherboard. Although the performance of the Taiwan capacitor is relatively poor, but if the PCB design of the main board and copper foil wiring are more standard, then there will be no problems in use, and the overfrequency of the main board using the Taiwan capacitor is not necessarily bad.
2, look at the capacity and temperature value:
Intel requires the filter capacitor of the CPU power supply circuit to have a single capacity of at least 1000μF. However, the current capacity is mostly between 2000μF and 4000μF. Some motherboards use a capacity of 5000μF. The capacitor capacity near the memory slot is mostly between 1000μF and 1500μF. The capacitor with a smaller capacity is difficult to provide sufficient pure current to the CPU and memory. The incompatibility problem after upgrading the CPU on some old motherboards actually comes from this.
Heat resistance value, on the other hand also illustrates the quality of capacitor, the capacitance value of heat-resistant motherboard is 105 ℃, and if your motherboard condenser heat resistance value is 85 ℃, the most is the result of the vendor too save materials, low voltage values of capacitance on the use of no problem, but when the CPU overclocking status occurred in the pulp "risk is bigger.
Misunderstandings about motherboard capacitance:
1. The larger the capacitance, the better:
Generally speaking, the larger the capacitance, the better, but this is not absolute, large capacity capacitance is not easy to filter out high-frequency interference signals, and multiple small capacity capacitance in parallel is more effective and stable than a single large capacity capacitance.
Moreover this and main line, power | regulator design also has a certain relationship, but if your motherboard is everywhere around 100 mu F small capacitance, the motherboard quality were not much better.
2, Japanese capacitor must be suitable for overclocking:
Many friends think that the use of Japanese capacitor motherboard overclocking must be good. In fact, overclocking is not only related to capacitance, but also related to the circuit design of the main board, clock chip, power supply, BIOS design, etc., not relying on capacitance alone can decide, some of the mainboard using GSC capacitor overclocking is also very good. But the Japanese capacitor is helpful to the stability of the motherboard.
3, with high quality capacitor motherboard must be good:
Not necessarily, as stated at the beginning of this article, a good motherboard will certainly use a good capacitor, but a good capacitor motherboard is not necessarily a good motherboard. A good motherboard not only to see the pros and cons of capacitance, but also to see the design level of the motherboard, such as Asustek, Microstar such large factory is not commonly used RUBYCON, NICHICON capacitor, but their product wiring, PCB design is first-class, so it also ensures the stability of its products; On the contrary, some small factories in order to attract buyers, often use some good capacitance, but its wiring, power supply design, MOSFET quality is very general, such a motherboard often looks good, but with a long time it is hard to say.
Capacitors or recommended to choose a large brand. Big brand products, will have a set of perfect strict inspection, evaluation measures, quality assurance. This also means that the cost is high, the big brand of high quality capacitor with a small factory capacitor products between nearly 20% to 40% of the price difference. However, products from small factories have greater risks, such as poor quality materials and inferior capacitors, which will have adverse effects on the stability and compatibility of the system.