Introduction to UC3845 PWM Controller

Hi Friends! Hope you are doing well. Today, I’ll cover the details of the Introduction to UC3845 PWM Controller.

In this post, we’ll discuss each and everything related to UC3845, its pinout and description, main features, block diagram, marking diagram and applications). Let’s dive right in and explore everything you need to know.

The UC3845 is a high-performance fixed-frequency current-mode controller for offline and DC-to-DC converter applications that offers designers a cost-effective option with few external components. Fine-tunable oscillators, precise duty cycle control, temperature compensation references, and high-gain error amplifiers are all included in these integrated circuits. For driving power MOSFETs, the current sampling comparator and high current totem pole output are excellent components. UVLO thresholds of 16V (on) and 10V (off) are used in the UC3842 and UC3844 (off). The UC3843 and UC3845 operate at 8.5V and 7.9V, respectively (off).

Protective features include input and reference undervoltage lockouts with hysteresis, cycle by cycle current limiting, a latch for single pulse metering, and a flipflop that blanks the output of every other oscillator cycle, allowing output dead periods of 50% to 70% to be programmed.

These devices come in both an 8pin dualinline plastic container and a 14pin plastic surface mount (SOIC14) package. For the totem pole output stage, the SOIC 14 package features separate power and ground pins. UVLO thresholds of 16 V (on) and 10 V (off) make the UCX844 excellent for off-line converters. With UVLO thresholds of 8.5 V (on) and 7.6 V (off), the UCX845 is designed for lower voltage applications (off).

In total, UC3845 is specially designed for low voltage applications.

2. CAD Model

The following figures are the Symbol, Footprint and 3D Model of UC3845.

Symbol

Footprint

3D Model

3. Features

• Current Mode Operation To 500 kHz Output Switching Frequency

• Output Deadtime Adjustable From 50% To 70%

• Automatic Feed Forward Compensation

• Latching PWM For Cycle−By−Cycle Current Limiting

• Internally Trimmed Reference With Undervoltage Lockout

• High Current Totem Pole Output

• Input Undervoltage Lockout With Hysteresis

• Low Startup And Operating Current

• Direct Interface With ON Semiconductor SENSEFET Products

• Pb−Free Packages Are Available

4. Functional Block Diagram

5. Marking Diagram

6. Circuit

7. Applications

● Battery Drain Circuit

● Electronics Power Supply

● Load Machines

● SMPS (Switch Mode Power Supplies) Circuits

● DC-DC Converter Circuits

8. Package

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