The biggest difference between UC3842 and UC3843 PWM controllers is in their electrical features and what they are used for. UC3842 can work with higher voltages and faster switching speeds. This makes it good for power projects that need high voltage and high frequency. UC3843 works with lower voltages but gives more current from its output pin. This makes it better for power supplies that need low voltage but high current. Both ICs use pulse width modulation and act as current-mode pwm controller devices in power systems. But each integrated circuit is made for different needs. The table below shows how each pwm IC is unique:
| Specification | UC3842 | UC3843 |
|---|---|---|
| Operating Voltage Range | 12V to 28V | 7.0V to 8.2V |
| Output Pin Current | 200 mA | 1A |
| Switching Frequency | Up to 500 kHz | Typically 52 kHz |
| Typical Application | DC-DC, offline converters | Low voltage, high current use |
Knowing the difference between UC2842 and UC3842 helps designers pick the right pwm IC for each power project.
Key Takeaways
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UC3842 is good for power supplies with high voltage and high frequency. UC3843 is better for things that need low voltage and high current.
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UC2842 can work in very hot or cold places. This makes it great for factories and outside use.
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UC3842 and UC3843 both have the same 8-pin shape. You can switch them if the voltage and current are right.
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UVLO keeps controllers safe by turning them off at bad voltages. UC3842 needs a higher voltage to turn on than UC3843.
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Picking the right controller helps your power supply work better. It also makes it safer and more reliable for your project.
Quick Comparison
Key Specs
When people compare UC3842 and UC3843, they check the datasheet specs. Both pwm controllers have many things in common, but some things are different. The table below puts their main technical details next to each other:
| Parameter | UC3842 | UC3843 |
|---|---|---|
| Controller Type | Current-mode pwm controller | Current-mode pwm controller |
| Pin Count | 8 pins | 8 pins |
| Operating Voltage Range | 12V to 28V | 7.0V to 8.2V |
| Output Pin Current | 200 mA | 1 A |
| Maximum Duty Cycle | Up to 97% | Up to 100% |
| Typical Oscillation Frequency | Up to 500 kHz | 52 kHz |
| Operating Temperature | 0°C to 70°C | 0°C to 70°C |
| UVLO Threshold (Turn-on) | 16 V | 8.5 V |
These important specs help engineers pick the right ic for their power supply. Each ic’s datasheet lists these numbers to help users choose the best pwm controller for their project.
Main Differences
UC3842 and UC3843 pwm controllers have special features that change how they work in circuits. UC3842 can use a higher voltage range, so it is better for systems that need more voltage. UC3843 gives more current from its output pin, so it works well in power supplies that need to run bigger loads.
Note: UC3843 can have a duty cycle up to 100%. This means it can keep the output on for the whole pwm cycle if needed. UC3842 has a lower duty cycle, so it might not work for some high-power uses.
The UVLO threshold is also different. UC3842 turns on at a higher voltage, which helps protect it in circuits with more voltage. UC3843 starts at a lower voltage, so it is good for low-voltage power supplies.
Both ics use current-mode pwm controller technology, but their specs and datasheet numbers show why each one fits different power jobs. These differences help engineers pick the right pwm controller for their project’s needs.
Difference Between UC2842 and UC3842
Temperature Range
UC3842 and UC2842 have different temperature ratings. UC3842 works best in places like offices and stores. These places usually stay between 0°C and 70°C. This is a normal temperature range for indoor areas. UC2842 can handle much colder and hotter places. It works from –40°C to 85°C. This means UC2842 is good for factories and outdoor machines. It can work when it is very hot or very cold. That is why engineers pick UC2842 for tough jobs.
| Controller | Ambient Operating Temperature Range | Typical Application Environment | Implication for Use |
|---|---|---|---|
| UC3842 | 0°C to 70°C | Commercial | Designed for stable, controlled environments, suitable for commercial power supplies |
| UC2842 | –40°C to 85°C | Industrial and commercial | Robust for industrial use with exposure to extreme temperatures |
UC2842 keeps working even in very hot or cold weather. This is the biggest difference for engineers who need strong power in hard places.
Application Suitability
Where you use UC3842 or UC2842 depends on the job. UC3842 is good for things like battery chargers and indoor power supplies. These devices stay inside and do not get too hot or cold. UC2842 can be used in both indoor and outdoor places. It works well in factories and outside machines. It is made for places where the temperature changes a lot.
| Parameter | UC2842 | UC3842 |
|---|---|---|
| Ambient Operating Temperature | –40°C to 85°C | 0°C to 70°C |
| Recommended Application Env. | Harsh temperature conditions | Moderate temperature ranges |
| Typical Applications | SMPS, DC-DC converters, power supplies, battery drain circuits, load machines | SMPS, DC-DC converters, power supplies, battery drain circuits, load machines |
Engineers like UC2842 because it is tough. It works in places where machines run all day and night. It is also good when the weather changes fast. The main difference matters most when the place is not climate-controlled.
There are other things to think about too. UC2842 usually needs less current to start up. This helps save energy when turning on. It can also be used in more custom designs. In factories, engineers want features like:
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High efficiency and power density to save energy and keep cool.
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Strong protection from too much current or heat.
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Good cooling, sometimes with PWM fan controllers that change speed.
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Reliable work even with electrical noise or shaking.
UC2842 stands out in these hard places. Its design helps machines keep running safely, even when things get rough. That is why many engineers pick UC2842 for important jobs.
Tip: Always check the temperature range and protection features before choosing. The difference between UC2842 and UC3842 can decide if your power supply lasts a long time or breaks early in a tough place.
Duty Cycle and UVLO
Maximum Duty Cycle
The maximum duty cycle tells how long the pwm controller keeps the output switch on during each cycle. The UC3842 ic supports a maximum duty cycle of up to 100%. This means the ic can keep the switch on for the whole pwm cycle if needed. This feature helps the ic transfer more energy and improve efficiency in power supply designs. The current-mode architecture of the ic also makes it respond quickly to changes in load. This keeps the output voltage steady and helps the power supply work well even when the load changes fast.
The UC3843 ic also works as a current-mode pwm controller. It usually runs at about 50 kHz. The design of this ic lets it adjust the duty cycle to handle changes in input voltage and load. This ability helps the ic keep the output voltage stable. Both controllers use feedback mechanisms for pwm signal modulation. These feedback systems help the ic adjust the duty cycle and keep the power supply working smoothly.
A high maximum duty cycle gives more flexibility. It lets the pwm ic handle tough power jobs and keep energy losses low.
UVLO Thresholds
UVLO stands for Under-Voltage Lockout. This feature protects the pwm ic from running when the supply voltage is too low. Each ic has its own UVLO threshold. The table below shows the values:
| Feature | UC3842 | UC3843 |
|---|---|---|
| UVLO Threshold (On) | 16V | 8.5V |
| UVLO Threshold (Off) | 10V | 7.9V |
| Application | High-voltage | Lower voltage |
When the voltage drops below the UVLO threshold, the ic stops working and enters a safe state. The output driver goes to high impedance, so the circuit does not switch by accident. This keeps the pwm ic safe from damage. The higher UVLO of the UC3842 makes it better for high-voltage power supplies. The lower UVLO of the UC3843 fits low-voltage or battery-powered devices.
UVLO helps make sure the pwm controller only works when the voltage is safe. This protects the ic and the whole power supply.
Choosing the Right Controller
Design Needs
Picking the right PWM controller depends on what your power supply needs. Engineers have to check a few things before they decide. The table below compares important features for UC3842 and UC3843:
| Factor | UC3842 | UC3843 |
|---|---|---|
| Operating Voltage Range | High-voltage applications | Lower voltage applications |
| UVLO Threshold (On) | 16V | 8.5V |
| UVLO Threshold (Off) | 10V | 7.9V |
| Application Focus | Industrial power supplies, flyback converters | Battery-powered devices, portable electronics |
| Additional Features | N/A | Soft-start, Overvoltage Protection, Internal Temperature Compensation |
| Pin Layout | Same as UC3843 (allows easy swapping) | Same as UC3842 (allows easy swapping) |
| Current Handling | Suitable for higher current industrial loads | Suitable for lower current portable devices |
| Control Modes | Voltage mode PWM | Voltage and current mode PWM (energy saving) |
Engineers need to pick a controller that matches the system’s voltage and current. UC3842 is best for high-voltage power supplies in factories. UC3843 works better in battery-powered or portable devices. These devices need lower voltage and extra protection. Both controllers have the same pin layout, so you can swap them easily.
Tip: To get the best power efficiency, use good MOSFETs and Schottky diodes. Also, make sure to manage heat and design the PCB well. These steps help keep the voltage steady and the power supply reliable.
Typical Applications
UC3842 and UC3843 are both important in today’s power systems. Which one you use depends on the power supply type and where it will be used. Here are some common uses for each:
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UC3842:
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Used in DC-DC converters and switch-mode power supplies.
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Works with boost, flyback, buck, forward, and push-pull converters.
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Powers big machines and advanced power supplies.
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Gives steady voltage and current for safe operation.
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Can be used in both isolated and non-isolated power supplies.
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UC3843:
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Used in switch-mode power supplies and DC-DC converters.
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Gives accurate voltage and current control in power supplies.
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Helps save energy in telecom and car systems.
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Used in renewable energy, like solar panel boost converters.
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Supports dual-loop control for voltage and current, which is good for combining power from different sources.
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Engineers pick UC3842 for power supplies in factories that need to handle lots of power and tough jobs. UC3843 is great for portable electronics and renewable energy systems. These need careful control and energy savings. Both controllers help make sure power conversion is efficient and voltage stays steady in many different power systems.
Compatibility Notes
Pinout
UC3842 and UC3843 have the same pin layout. Both chips come in an 8-pin package. The pins are called VFB, Current Sense, RT/CT, Output, VREF, and Ground. Because the pins match, engineers can swap these chips on the same board. The datasheet for each chip shows what each pin does. If you look at the datasheet pdf, you will see the pin numbers and names are the same.
Tip: Always check the datasheet before changing a chip. Even if the pins match, other details might be different.
Interchangeability
Many engineers wonder if they can use UC3842 and UC3843 in the same circuit. Both chips do similar jobs and can often be swapped. But there are some important differences to think about. The table below shows the main features:
| Feature | UC3842 | UC3843 |
|---|---|---|
| Supply Voltage Range | 12V to 28V | 7V to 8.2V |
| Output Current Capability | Up to 200mA | Up to 1A |
| Undervoltage Lockout | Not built-in (less precise) | Built-in undervoltage lockout |
| Typical Applications | Broad voltage range SMPS, DC-DC converters | Optimized for narrow voltage range power supplies |
| Pin Functions | VFB, Current Sense, RT/CT, Output, VREF, Ground (similar to UC3843) | Same as UC3842 |
| Oscillator and Timing | High switching frequency capability | Enhanced response time and simplified feedback |
| Practical Interchangeability | Possible with attention to voltage and current specs | Possible with attention to voltage and current specs |
| Limitations | Requires higher supply voltage; lower output current | Narrow voltage range; higher output current; requires current limiting resistor |
Both chips fit in the same socket, but the circuit must match the chip’s needs. UC3842 works best with higher supply voltage. UC3843 gives more output current but needs lower supply voltage. The datasheet pdf for each chip explains these limits. If the circuit does not meet the chip’s needs, the power supply might not work or could break.
Note: Always read the datasheet and check voltage and current before swapping these chips. This helps keep the circuit safe.
UC3842, UC3843, and UC2842 each have their own jobs in power supply design. UC3842 is good for high-voltage and factory uses. UC3843 works best in circuits with low voltage and lots of current. UC2842 is special because it can handle places that get very hot or cold. Engineers pick controllers with advanced PWM techniques for better power and less distortion. This is important in things like solar panels and factory machines. Picking the right controller helps the power supply work well, stay safe, and last a long time.
FAQ
What is the main function of a PWM controller like UC3842 or UC3843?
A PWM controller manages the switching of power devices. It controls how long the switch stays on or off. This helps regulate voltage and current in power supplies.
Can engineers swap UC3842 and UC3843 in the same circuit?
Engineers can swap these chips if the circuit matches the voltage and current needs of each IC. Always check the datasheet before making changes.
Why does the UVLO threshold matter in power supply design?
The UVLO threshold protects the controller from low voltage. It keeps the IC from working when the supply voltage drops too low. This helps prevent damage.
Which controller works better in extreme temperatures?
UC2842 works better in extreme temperatures. It operates from –40°C to 85°C. This makes it suitable for outdoor or industrial environments.
Do UC3842 and UC3843 have the same pinout?
Yes, both controllers have the same 8-pin layout. This allows easy replacement on the same circuit board.
Written by Jack Elliott from AIChipLink.
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