Overview
The UC3842BD1G is a high-performance, fixed-frequency current mode controller produced by onsemi. It is specifically designed for off-line and DC-DC converter applications, offering a cost-effective solution with minimal external components. This integrated circuit 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 ideal for driving power MOSFETs. The device includes protective features such as input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| VCC, VC | - | - | 30 | V |
| Total Power Supply and Zener Current (ICC + IZ) | - | - | 30 | mA |
| Output Current, Source or Sink | - | - | 1.0 | A |
| Output Energy (Capacitive Load per Cycle) | - | - | 5.0 | μJ |
| Reference Output Voltage (IO = 1.0 mA, TJ = 25°C) | 4.95 | 5.0 | 5.05 | V |
| Oscillator Frequency | - | 250 | - | kHz |
| Startup Threshold (VCC) | 8.5 | - | - | V |
| Operating Temperature Range | -40 | - | 105 | °C |
Key Features
- Trimmed Oscillator for Precise Frequency Control: The oscillator frequency is programmed by the values chosen for the timing components RT and CT, ensuring precise duty cycle control.
- Current Mode Operation: The device operates in current mode, where output switch conduction is initiated by the oscillator and terminated when the peak inductor current reaches the threshold level established by the Error Amplifier Output.
- Automatic Feed Forward Compensation: This feature helps in maintaining stable operation under varying conditions.
- Latching PWM for Cycle-by-Cycle Current Limiting: Ensures that only a single pulse appears at the output during any given oscillator cycle, providing robust current limiting.
- Internally Trimmed Reference with Undervoltage Lockout: Features a temperature-compensated reference and undervoltage lockout with hysteresis for reliable operation.
- High Current Totem Pole Output: Ideal for driving power MOSFETs with high current capability.
- Low Startup and Operating Current: Minimizes power consumption during startup and operation.
- Pb-Free and Halide-Free Device: Compliant with environmental regulations.
Applications
The UC3842BD1G is suitable for various power conversion applications, including:
- Off-Line Converters: Designed for use in off-line power supplies where high efficiency and reliability are crucial.
- DC-DC Converters: Ideal for DC-DC conversion applications requiring precise control and high performance.
- Switch Mode Power Supplies: Used in switch mode power supplies where current mode control is necessary.
Q & A
- What is the primary function of the UC3842BD1G?
The UC3842BD1G is a high-performance, fixed-frequency current mode controller designed for off-line and DC-DC converter applications.
- What is the typical oscillator frequency of the UC3842BD1G?
The oscillator frequency is guaranteed at 250 kHz.
- What are the key protective features of the UC3842BD1G?
The device includes input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering.
- What is the maximum output current of the UC3842BD1G?
The maximum output current is 1.0 A.
- What is the operating temperature range of the UC3842BD1G?
The operating temperature range is from -40°C to 105°C.
- What type of package is the UC3842BD1G available in?
The device is available in 8-pin dual-in-line and surface mount (SOIC-8) packages, as well as a 14-pin surface mount (SOIC-14) package.
- How is the oscillator frequency programmed in the UC3842BD1G?
The oscillator frequency is programmed by the values chosen for the timing components RT and CT.
- What is the purpose of the current sense comparator in the UC3842BD1G?
The current sense comparator monitors the inductor current and compares it to a level derived from the Error Amp Output to control the peak inductor current.
- Is the UC3842BD1G Pb-Free and Halide-Free?
Yes, the UC3842BD1G is Pb-Free and Halide-Free, making it compliant with environmental regulations.
- What are some common applications of the UC3842BD1G?
The UC3842BD1G is commonly used in off-line converters, DC-DC converters, and switch mode power supplies.
