Can UC3843B and UC3845BN be replaced?

No, the start-up voltage and cut-off voltage of the two of them are not the same. If you replace it, there may be no problem with the test machine, but there will be problems during normal operation.

Generally speaking, UC3845BN cannot replace UC3843B. Because the supply voltage of UC3845BN is between 15V and 25V, and the supply voltage of UC3843B is 12V, it will not start and have no output due to low voltage after substitution; When the input voltage of UC3843B is not higher than 15V, the current can be replaced by UC3845BN within the normal value, but UC3845BN is more resistant to power supply and output voltage, current value and temperature value, especially in areas with large voltage fluctuations, or when using generators to supply power, the advantages are more obvious, so the service life is longer in specific circuits.

No, I tried, it turns out that UC3843BN can't be used to replace UC3845B, no output voltage!

The difference between UC2845 and UC3845 is that the operating temperature is different.

The working temperature of UC2845 is 40°C to 85°C, but the working temperature of UC3845 is 0°C to 70°, the IC starting with 0°C to 70° is an industrial-grade collector circuit, and the UC3XX starts with a civilian-grade integrated circuit. Therefore, when the requirements are different, such as when the temperature is low in the north, UC3845 cannot be directly replaced by UC2845. UCX845 Single-Ended 500kHz Current Mode PWM Controller.

The UCX84x family of control ICs provides the functionality required for implementation, either offline or DC-to-DC fixed-frequency current-mode control schemes, with a minimum number of external components. Internally implemented circuitry includes undervoltage lockout (UVLO) with a start-up current of less than 1mA and high accuracy, a reference at an error amplifier that is fine-tuned for accuracy inputs, other internal circuitry includes logic to ensure latching operation, a pulse-width modulated PWM comparator that also provides current-limit control, and a totem-pole output stage, designed for source or sink peak currents. The output stage is suitable for driving N-channel MOSFETs.

UC3842 and 3845 are not universal. There is a big gap between the two IC driving voltages, and the replacement will change the voltage, which is not usable, and it is felt that once the exchange will lead to the instability of the motherboard voltage, the CPU power supply is insufficient, and the phenomenon of Caton cannot be turned on, which cannot ensure the normal operation of the CPU, which can not be replaced, and can only be guaranteed by replacing the same model.

Features of UC3842:Integrated circuit is a kind of miniature electronic device or component, using a certain process to interconnect the transistor resistors, capacitors and inductors and other components and wiring required in a circuit, and make them on a small piece or several small pieces of semiconductor wafer or dielectric substrate, and then encapsulate in a tube shell to become a miniature structure with the required circuit function.

It is a new type of semiconductor device developed from the late 50s to the 60s of the 20th century.

It is a semi-conductive manufacturing process of Hu Cong through oxidation, lithography, diffusion, epitaxy, evaporated aluminum, etc., in which the semiconductor resistors, capacitors and other components required to form a circuit with a certain function and the connecting wires between them are all integrated on a small piece of silicon wafer, and then soldered and encapsulated in a tube shell of electronic devices.

UC3843BN and UC3843AN have internally different circuits.

UC3843AN and UC3843BN are internal versions, the difference is that UC3843BN has made some improvements on the basis of UC3843AN.

1. UC3843 is the general structure of the entire BN and AN, etc., just like a branch under the parent company.

2. The starting voltage of UC3843 is greater than that, the closing voltage is greater, and the maximum input voltage is 30V.

Generally speaking, it works on, but the voltage between the start-up flashes needs to be higher than that of the field dust. So at this time, the output voltage of UC3843BN and UC3843AN is the same.

Third, whether the two can be replaced, because the starting and cut-off voltages of the two are different, and UC3842BN is based on UC3843AN to make some improvements, if you want to replace the need, you can change the starting circuit and self-supply circuit.

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The UC3845 and UC3842 are mixed-signal controllers that are widely used in medium and high power applications such as switching power supplies, voltage regulators, DC-DC converters and inverters. They have similar chip architectures, functions, and pin definitions, so they are considered by many to be the same chips that can be used interchangeably. However, this statement is not entirely true.

In practical applications, there are many differences between the parameters and characteristics of UC3845 and UC3842, mainly including: control mode, frequency, leakage induction current protection, correction circuit, threshold and dead time control, etc. Therefore, while both have the same number and type of pins, their functions and features are different and the UC3842 cannot be directly replaced with UC3845 or vice versa.

If they are used interchangeably in different circuits, they may lead to problems such as degraded control performance, unstable waveforms, and insufficient vertical power of the chip. Therefore, if the chip needs to be replaced or replaced, it is recommended to carefully check the chip manual to ensure that it has the same electrical characteristics, otherwise the stability and function of the circuit may be destroyed by the bad ruler. In other words, UC3845 is not recommended to be replaced by UC3842, and must be selected according to the actual circuit design requirements.

Replace UC3845 what to test pro, hello, glad for your question. 1. Check the voltage of the seventh pin of UC3845, the voltage is about 8V when the switching power supply is not working, and check that the positive output terminal of the rectifier bridge is connected to the two series start buck resistors of the seventh pin of UC3845, which is normal. 2. Check the filter capacitor connected to the power supply end of the seventh pin of UC3845, after the test, only slightly feel that the dry capacity of the bridge decreases, after replacing the reactive power of other main parts, replace the original capacitor with a 50V220UF electrolytic capacitor, after welding, power on the test machine, the switching power supply begins to work normally, at this time, the voltage of the seventh pin of 3845 has been around the detection, the circuit is working normally, and the open circuit value of each output voltage such as +5V and +12V is normal, 3. Turn off the power supply, Connect the switch load to the output end of the switching power supply, start the test machine, work normally, detect the loading value of each output voltage such as +5V and +12V, and bake the machine for an hour, and the working temperature rise is normal.

Precautions: When encountering the failure of UC3845 without vibration, first check whether the rectifier bridge and switch tube are damaged, if there is no damage, do not blindly replace the chip, you can directly replace the starting filter capacitor test machine.

Dear, I'm glad to answer for you: what to test to replace UC3845 Answer: Dear, replace UC3845 to test as follows 1. Check the voltage of the seventh pin of UC3845, the voltage is about 8V when the switching power supply is not working, check that the positive output end of the rectifier bridge is connected to the two series start buck resistors of the seventh pin of UC3845, which is normal.

2. Check the filter capacitor connected to the power supply end of the seventh pin of UC3845, after the test, only slightly feel that the capacity decreases, after replacing the reactive power of other main parts, replace the original capacitor with a 50V220UF electrolytic capacitor, after welding, power on the test machine, the switching power supply begins to work normally, at this time, the voltage of the seventh pin of the hail detection 3845 is already around, the circuit works normally, the open circuit value of each output voltage such as +5V and +12V is normal, and the meaning of replacing it is to transform, The feast is new. Substitution means substitution. The difference between the two words is that they point to different things.

One is mostly used to refer to the replacement of the same thing from the original to the new, and the other is to replace one thing with another. For example. Recently, there have been frequent problems with the machine, and it should be better if the old parts were replaced with new ones.

The processor of the 3842A is dual-core and dual-threaded, and the running score is 10,000, while the processor of the 3842B is four-core and four-threaded, and the running score is 20,000, the difference is that the processing speed of the processor is different.

The UC3845 is a high-performance fixed-frequency current-mode controller designed for offline and DC-to-DC converter applications, providing designers with a cost-effective solution with minimal external components. These ICs feature a fine-tunable oscillator, precise duty cycle control, temperature-compensated references, and high-gain error amplifiers. The current sampling comparator and high-current totem pole output are ideal devices for driving power MOSFETs.