Overview
The UC3845AN is a current-mode PWM (Pulse Width Modulation) controller integrated circuit produced by Texas Instruments. This device is part of the UCx84x series, which is optimized for off-line and DC-to-DC converters. It features a low start-up current, automatic feedforward compensation, pulse-by-pulse current limiting, and enhanced load-response characteristics. The UC3845AN is suitable for a wide range of power supply applications, including switching regulators and transformer-coupled DC-DC converters.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Manufacturer | Texas Instruments | |
| Package Type | PDIP-8 | |
| Output Current | 1 A | |
| Maximum Switching Frequency | 500 kHz | |
| Topology | Boost, Buck, Flyback, Forward | |
| Maximum Duty Cycle | 50% | |
| Undervoltage Lockout (UVLO) | 8.4V / 7.6V | |
| Operating Temperature Range | 0°C to 70°C | |
| Pin Count | 8 | |
| Rise Time | 50 ns | |
| Fall Time | 50 ns |
Key Features
- Low start-up current (< 1 mA)
- Automatic feedforward compensation
- Pulse-by-pulse current limiting
- Enhanced load-response characteristics
- Undervoltage lockout with hysteresis
- Double-pulse suppression
- High-current totem-pole output
- Internally trimmed bandgap reference
- Error amplifier with low output resistance
Applications
The UC3845AN is suitable for various power supply applications, including:
- Switching regulators of any polarity
- Transformer-coupled DC-DC converters
- Off-line power supplies
- DC-DC converters
Q & A
- What is the maximum switching frequency of the UC3845AN?
The maximum switching frequency of the UC3845AN is 500 kHz.
- What is the output current capability of the UC3845AN?
The UC3845AN can handle an output current of up to 1 A.
- What are the operating temperature ranges for the UC3845AN?
The UC3845AN operates within a temperature range of 0°C to 70°C.
- What topologies does the UC3845AN support?
The UC3845AN supports boost, buck, flyback, and forward topologies.
- What is the undervoltage lockout (UVLO) threshold for the UC3845AN?
The UVLO thresholds for the UC3845AN are 8.4V and 7.6V.
- What is the maximum duty cycle of the UC3845AN?
The maximum duty cycle of the UC3845AN is 50%.
- What package types are available for the UC3845AN?
The UC3845AN is available in a PDIP-8 package.
- What are some key features of the UC3845AN?
Key features include low start-up current, automatic feedforward compensation, pulse-by-pulse current limiting, and an internally trimmed bandgap reference).
- What are typical applications for the UC3845AN?
Typical applications include switching regulators, transformer-coupled DC-DC converters, off-line power supplies, and DC-DC converters).
- How do I set the switching frequency for the UC3845AN?
The switching frequency can be set using the timing resistor (RRT) and capacitor (CCT) connected to the RT/CT pin, with the frequency estimated by the equation fOSC = 1.72 / (RRT × CCT)).
