UC3844 PWM Controller: Uses, Pinout and Datasheet
14 Terminals 10V~30V 14-Pin UC3844 DC to DC converter IC SWITCHING CONTROLLER 1 Outputs Up to 500kHz Transistor Driver









14 Terminals 10V~30V 14-Pin UC3844 DC to DC converter IC SWITCHING CONTROLLER 1 Outputs Up to 500kHz Transistor Driver
UC3844 is a current PWM controller. This article mainly introduce its uses, pinout, datasheet and other detailed information about On Semiconductor UC3844.

#138 UC3844 Current Mode SMPS Circuit - Circuit Explained with Troubleshooting
UC3844 Description
The UC3844 is fixed frequencycurrent-mode PWM controller. It is specially designed for Off-Line and DC to DC converter applications with minimum external components.
These integrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and a high current totempole output for driving a Power MOSFET.
The UC3844 have UVLO thresholds of 16V (on) and 10V (off) and can operate with 50% duty cycle.
UC3844 Pinout

UC3844 CAD Model
Symbol

Footprint

3D Model

UC3844 Features
1.Current-Mode PWM controller
2.Operating Voltage: 12V to 28V
3.Output pin current: 200 mA
4.Switching Frequency: 500 kHz
5.Duty Cycle - Max: 100 %
6.Operating Supply Current:25 mA
7.Optimized for Off-line and DC-to-DC Converters
8.High-Current Totem-Pole Output
9.Output Deadtime Adjustable from 50% t
10.Low Start Up Current (<1mA)
11.Automatic Feed Forward Compensation
12. Pulse-by-pulse Current Limiting
13.Enhanced Load Response Characteristics
14.Under-voltage Lockout With Hysteresis
15.Double Pulse Suppression
16.Internally Trimmed Bandgap Reference
17.Low RO Error Amp
18.Maximum Duty Clamp
19.UVLO With Hysteresis
Specifications
- TypeParameter
- Mount
In electronic components, the term "Mount" typically refers to the method or process of physically attaching or fixing a component onto a circuit board or other electronic device. This can involve soldering, adhesive bonding, or other techniques to secure the component in place. The mounting process is crucial for ensuring proper electrical connections and mechanical stability within the electronic system. Different components may have specific mounting requirements based on their size, shape, and function, and manufacturers provide guidelines for proper mounting procedures to ensure optimal performance and reliability of the electronic device.
Surface Mount - Mounting Type
The "Mounting Type" in electronic components refers to the method used to attach or connect a component to a circuit board or other substrate, such as through-hole, surface-mount, or panel mount.
Surface Mount - Package / Case
refers to the protective housing that encases an electronic component, providing mechanical support, electrical connections, and thermal management.
14-SOIC (0.209, 5.30mm Width) - Number of Pins14
- Operating Temperature
The operating temperature is the range of ambient temperature within which a power supply, or any other electrical equipment, operate in. This ranges from a minimum operating temperature, to a peak or maximum operating temperature, outside which, the power supply may fail.
0°C~70°C TA - Packaging
Semiconductor package is a carrier / shell used to contain and cover one or more semiconductor components or integrated circuits. The material of the shell can be metal, plastic, glass or ceramic.
Tube - Published2002
- JESD-609 Code
The "JESD-609 Code" in electronic components refers to a standardized marking code that indicates the lead-free solder composition and finish of electronic components for compliance with environmental regulations.
e0 - Part Status
Parts can have many statuses as they progress through the configuration, analysis, review, and approval stages.
Obsolete - Moisture Sensitivity Level (MSL)
Moisture Sensitivity Level (MSL) is a standardized rating that indicates the susceptibility of electronic components, particularly semiconductors, to moisture-induced damage during storage and the soldering process, defining the allowable exposure time to ambient conditions before they require special handling or baking to prevent failures
1 (Unlimited) - Number of Terminations14
- ECCN Code
An ECCN (Export Control Classification Number) is an alphanumeric code used by the U.S. Bureau of Industry and Security to identify and categorize electronic components and other dual-use items that may require an export license based on their technical characteristics and potential for military use.
EAR99 - Terminal Finish
Terminal Finish refers to the surface treatment applied to the terminals or leads of electronic components to enhance their performance and longevity. It can improve solderability, corrosion resistance, and overall reliability of the connection in electronic assemblies. Common finishes include nickel, gold, and tin, each possessing distinct properties suitable for various applications. The choice of terminal finish can significantly impact the durability and effectiveness of electronic devices.
Tin/Lead (Sn/Pb) - Terminal Position
In electronic components, the term "Terminal Position" refers to the physical location of the connection points on the component where external electrical connections can be made. These connection points, known as terminals, are typically used to attach wires, leads, or other components to the main body of the electronic component. The terminal position is important for ensuring proper connectivity and functionality of the component within a circuit. It is often specified in technical datasheets or component specifications to help designers and engineers understand how to properly integrate the component into their circuit designs.
DUAL - Terminal Form
Occurring at or forming the end of a series, succession, or the like; closing; concluding.
GULL WING - Peak Reflow Temperature (Cel)
Peak Reflow Temperature (Cel) is a parameter that specifies the maximum temperature at which an electronic component can be exposed during the reflow soldering process. Reflow soldering is a common method used to attach electronic components to a circuit board. The Peak Reflow Temperature is crucial because it ensures that the component is not damaged or degraded during the soldering process. Exceeding the specified Peak Reflow Temperature can lead to issues such as component failure, reduced performance, or even permanent damage to the component. It is important for manufacturers and assemblers to adhere to the recommended Peak Reflow Temperature to ensure the reliability and functionality of the electronic components.
240 - Time@Peak Reflow Temperature-Max (s)
Time@Peak Reflow Temperature-Max (s) refers to the maximum duration that an electronic component can be exposed to the peak reflow temperature during the soldering process, which is crucial for ensuring reliable solder joint formation without damaging the component.
30 - Base Part Number
The "Base Part Number" (BPN) in electronic components serves a similar purpose to the "Base Product Number." It refers to the primary identifier for a component that captures the essential characteristics shared by a group of similar components. The BPN provides a fundamental way to reference a family or series of components without specifying all the variations and specific details.
UC3844 - Function
The parameter "Function" in electronic components refers to the specific role or purpose that the component serves within an electronic circuit. It defines how the component interacts with other elements, influences the flow of electrical signals, and contributes to the overall behavior of the system. Functions can include amplification, signal processing, switching, filtering, and energy storage, among others. Understanding the function of each component is essential for designing effective and efficient electronic systems.
Step-Up, Step-Up/Step-Down - Number of Outputs1
- Output Voltage
Output voltage is a crucial parameter in electronic components that refers to the voltage level produced by the component as a result of its operation. It represents the electrical potential difference between the output terminal of the component and a reference point, typically ground. The output voltage is a key factor in determining the performance and functionality of the component, as it dictates the level of voltage that will be delivered to the connected circuit or load. It is often specified in datasheets and technical specifications to ensure compatibility and proper functioning within a given system.
5.1V - Output Type
The "Output Type" parameter in electronic components refers to the type of signal or data that is produced by the component as an output. This parameter specifies the nature of the output signal, such as analog or digital, and can also include details about the voltage levels, current levels, frequency, and other characteristics of the output signal. Understanding the output type of a component is crucial for ensuring compatibility with other components in a circuit or system, as well as for determining how the output signal can be utilized or processed further. In summary, the output type parameter provides essential information about the nature of the signal that is generated by the electronic component as its output.
Transistor Driver - Input Voltage-Nom
Input Voltage-Nom refers to the nominal or rated input voltage that an electronic component or device is designed to operate within. This parameter specifies the voltage level at which the component is expected to function optimally and safely. It is important to ensure that the actual input voltage supplied to the component does not exceed this nominal value to prevent damage or malfunction. Manufacturers provide this specification to guide users in selecting the appropriate power supply or input voltage source for the component. It is a critical parameter to consider when designing or using electronic circuits to ensure reliable performance and longevity of the component.
15V - Analog IC - Other Type
Analog IC - Other Type is a parameter used to categorize electronic components that are integrated circuits (ICs) designed for analog signal processing but do not fall into more specific subcategories such as amplifiers, comparators, or voltage regulators. These ICs may include specialized analog functions such as analog-to-digital converters (ADCs), digital-to-analog converters (DACs), voltage references, or signal conditioning circuits. They are typically used in various applications where precise analog signal processing is required, such as in audio equipment, instrumentation, communication systems, and industrial control systems. Manufacturers provide detailed specifications for these components to help engineers select the most suitable IC for their specific design requirements.
SWITCHING CONTROLLER - Operating Supply Current
Operating Supply Current, also known as supply current or quiescent current, is a crucial parameter in electronic components that indicates the amount of current required for the device to operate under normal conditions. It represents the current drawn by the component from the power supply while it is functioning. This parameter is important for determining the power consumption of the component and is typically specified in datasheets to help designers calculate the overall power requirements of their circuits. Understanding the operating supply current is essential for ensuring proper functionality and efficiency of electronic systems.
17mA - Nominal Supply Current
Nominal current is the same as the rated current. It is the current drawn by the motor while delivering rated mechanical output at its shaft.
17mA - Output Configuration
Output Configuration in electronic components refers to the arrangement or setup of the output pins or terminals of a device. It defines how the output signals are structured and how they interact with external circuits or devices. The output configuration can determine the functionality and compatibility of the component in a circuit design. Common types of output configurations include single-ended, differential, open-drain, and push-pull configurations, each serving different purposes and applications in electronic systems. Understanding the output configuration of a component is crucial for proper integration and operation within a circuit.
Positive - Output Current
The rated output current is the maximum load current that a power supply can provide at a specified ambient temperature. A power supply can never provide more current that it's rated output current unless there is a fault, such as short circuit at the load.
1A - Voltage - Supply (Vcc/Vdd)
Voltage - Supply (Vcc/Vdd) is a key parameter in electronic components that specifies the voltage level required for the proper operation of the device. It represents the power supply voltage that needs to be provided to the component for it to function correctly. This parameter is crucial as supplying the component with the correct voltage ensures that it operates within its specified limits and performance characteristics. It is typically expressed in volts (V) and is an essential consideration when designing and using electronic circuits to prevent damage and ensure reliable operation.
10V~30V - Control Features
Control features in electronic components refer to specific functionalities or characteristics that allow users to manage and regulate the operation of the component. These features are designed to provide users with control over various aspects of the component's performance, such as adjusting settings, monitoring parameters, or enabling specific modes of operation. Control features can include options for input/output configurations, power management, communication protocols, and other settings that help users customize and optimize the component's behavior according to their requirements. Overall, control features play a crucial role in enhancing the flexibility, usability, and performance of electronic components in various applications.
Frequency Control - Topology
In the context of electronic components, "topology" refers to the arrangement or configuration of the components within a circuit or system. It defines how the components are connected to each other and how signals flow between them. The choice of topology can significantly impact the performance, efficiency, and functionality of the electronic system. Common topologies include series, parallel, star, mesh, and hybrid configurations, each with its own advantages and limitations. Designers carefully select the appropriate topology based on the specific requirements of the circuit to achieve the desired performance and functionality.
Boost, Flyback - Control Mode
In electronic components, "Control Mode" refers to the method or mode of operation used to regulate or control the behavior of the component. This parameter determines how the component responds to input signals or commands to achieve the desired output. The control mode can vary depending on the specific component and its intended function, such as voltage regulation, current limiting, or frequency modulation. Understanding the control mode of an electronic component is crucial for proper integration and operation within a circuit or system.
CURRENT-MODE - Frequency - Switching
"Frequency - Switching" in electronic components refers to the rate at which a device, such as a transistor or switching regulator, turns on and off during operation. This parameter is crucial in determining the efficiency and performance of power converters, oscillators, and other circuits that rely on rapid switching. Higher switching frequencies typically allow for smaller component sizes but may require more advanced design considerations to manage heat and electromagnetic interference.
Up to 500kHz - Input Voltage (Max)
Input Voltage (Max) refers to the maximum voltage that an electronic component can safely handle without getting damaged. This parameter is crucial for ensuring the proper functioning and longevity of the component. Exceeding the maximum input voltage can lead to overheating, electrical breakdown, or even permanent damage to the component. It is important to carefully consider and adhere to the specified maximum input voltage when designing or using electronic circuits to prevent any potential issues or failures.
25V - Control Technique
In electronic components, "Control Technique" refers to the method or approach used to regulate and manage the operation of the component. This parameter is crucial in determining how the component functions within a circuit or system. Different control techniques can include analog control, digital control, pulse-width modulation (PWM), and various feedback mechanisms. The choice of control technique can impact the performance, efficiency, and overall functionality of the electronic component. It is important to select the appropriate control technique based on the specific requirements and characteristics of the application in which the component will be used.
PULSE WIDTH MODULATION - Rise Time
In electronics, when describing a voltage or current step function, rise time is the time taken by a signal to change from a specified low value to a specified high value.
45ns - Synchronous Rectifier
Synchronous rectification is a technique for improving the efficiency of rectification by replacing diodes with actively controlled switches, usually power MOSFETs or power bipolar junction transistors (BJT).
No - Fall Time (Typ)
Fall Time (Typ) is a parameter used to describe the time it takes for a signal to transition from a high level to a low level in an electronic component, such as a transistor or an integrated circuit. It is typically measured in nanoseconds or microseconds and is an important characteristic that affects the performance of the component in digital circuits. A shorter fall time indicates faster switching speeds and can result in improved overall circuit performance, such as reduced power consumption and increased data transmission rates. Designers often consider the fall time specification when selecting components for their circuits to ensure proper functionality and efficiency.
35 ns - Switcher Configuration
Switcher Configuration in electronic components refers to the arrangement or setup of a switcher circuit, which is a type of power supply that converts one form of electrical energy into another. The configuration of a switcher circuit includes the specific components used, such as transistors, diodes, capacitors, and inductors, as well as their interconnections and control mechanisms. The switcher configuration determines the efficiency, voltage regulation, and other performance characteristics of the power supply. Different switcher configurations, such as buck, boost, buck-boost, and flyback, are used for various applications depending on the desired output voltage and current requirements. Understanding and selecting the appropriate switcher configuration is crucial in designing reliable and efficient power supply systems for electronic devices.
SINGLE - Max Duty Cycle
Max Duty Cycle refers to the maximum percentage of time that an electronic component, such as a switch or a power supply, can be in an "on" state during a defined time period. It is an important parameter in pulse-width modulated (PWM) systems and helps determine how often a device can operate without overheating or sustaining damage. By specifying the maximum duty cycle, manufacturers provide guidance on the safe operational limits of the component, ensuring reliability and efficiency in various applications.
50 % - Duty Cycle (Max)
The "Duty Cycle (Max)" parameter in electronic components refers to the maximum percentage of time that a signal is active or on within a specific period. It is commonly used in components such as pulse-width modulation (PWM) controllers, oscillators, and timers. A duty cycle of 100% means the signal is always on, while a duty cycle of 0% means the signal is always off. Understanding the maximum duty cycle is important for ensuring proper operation and performance of the electronic component within its specified limits. It is typically expressed as a percentage and helps determine the amount of power or energy being delivered by the signal.
48% - Length8.65mm
- Width3.9mm
- RoHS Status
RoHS means “Restriction of Certain Hazardous Substances” in the “Hazardous Substances Directive” in electrical and electronic equipment.
RoHS Compliant
UC3844 Alternatives

Where to use UC3844?
The UC3844 IC is a current Mode PWM Controller, meaning it can be used to provide a constant current by varying the output voltage to the load.
This IC features a trimmed oscillator for precise duty cycle control, a temperature compensated reference, a high gain error amplifier, a current sensing comparator, and a high current totem pole output for driving a Power MOSFET. The UC3842 and UC3844 have the same UVLO thresholds of 16V (on) and 10V (off).
The UC3844 can be used to regulate or limit current in applications like SMPS, RPS, DC-DC Converters, Line voltage regulators, etc. So if you are looking for an IC to produce PWM signals for controlling a power switch based on the current flowing through the circuit, then this IC might be the right choice for you.
How to use UC3844?
Using UC3844 in a circuit is very simple as it requires a minimum number of components. A sample application circuit from the UC3844 datasheet is shown below.

The input voltage to the VCC pin should be 12V to 28v. The output pin of the IC is connected to the gate driver circuit of the Power switch which is to be switched. The VFB (Voltage feedback) pin acts as feedback based on which the PWM signal is controlled. A shunt resistor is used to monitor the change in current in the circuit, and then this difference voltage across the shunt is provided to the feedback pin. VREF is used to provide charging current to the oscillator timing capacitor through the timing resistor. It is important for reference stability that VREF is bypassed to GROUND with a ceramic capacitor connected as close to the pin as possible.
UC3844 Block Diagram

UC3844 Internal Block Diagram

UC3844 Applications
1.DC-DC converter circuits
2.Electronics power supply
3.Battery drain circuit
4.Load machines
5.SMPS (Switch Mode Power Supplies) circuits
UC3844 Manufacturer
ON Semiconductor is a semiconductor supplier company, Products include power and signal management, logic, discrete, and custom devices for automotive, communications, computing, consumer, industrial, LED lighting, medical, military/aerospace and power applications. ON Semiconductor runs a network of manufacturing facilities, sales offices and design centers in North America, Europe, and the Asia Pacific regions. Its headquarter is in Phoenix, Arizona.
Trend Analysis
Datasheet PDF
- Datasheets :
- ReachStatement :
1.Can the electric car charger UC3842 be replaced by UC3844?
The electric vehicle charger UC3842 cannot be replaced with UC3844. Both UC3842 and UC3844 are high-performance fixed-frequency current-mode controllers, and the device packaging and pin arrangement are exactly the same. Only the UC3842 chip can fine-tune the oscillator discharge current and accurately control the duty cycle, but UC3844 does not have this function, so UC3844 cannot be used to replace UC3842. UC3842 can be replaced by UC2842, UC2843, UC3843, and their parameters are exactly the same.
2.How to measure the quality of UC3844 with a multimeter?
First, set the range switch of the digital multimeter to the corresponding voltage range, then the black test lead is grounded, and the red test lead is connected to each pin of the chip under test. Then the measured data can be compared with the normal data of the chip to determine the The chip is normal or not.
3.What is the maximum current of the UC3844 current detection pin?
The maximum current is determined by the sampling resistance, and the maximum detection voltage of pin 3 is 1V. For example, if you use a 0.1Ω resistor, the maximum detection current is I=U/R=10A.
4.Can UC3844 replace UC3844B?
Yes, they can be replaced if they are the same internally. The performance is the same and can be replaced. N and D suffix packages are different. The industrial product 3844 has a wider applicable temperature range than the civilian product 3844b.
5.Why UC3844 switching power supply 7-pin voltage is 13V, eight-pin doesn’t have voltage?
The power supply pin of UC3844 can only start to work when it reaches 16V (5V voltage is generated on pin 8), and it stops working when it is lower than 10V after starting. So you must first determine whether the voltage of pin 7 can reach 16 or more. Check carefully whether there is any problem with the starting resistance and starting circuit.
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