Overview
The UC3842ADM, part of the UC3842A series, is a high-performance, fixed-frequency, current-mode controller produced by Microsemi Corporation (now part of onsemi). This integrated circuit is specifically designed for off-line and DC-to-DC converter applications, offering a cost-effective solution with minimal external components. It features a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, a high-gain error amplifier, and a current sensing comparator. The device is particularly suited for driving power MOSFETs due to its high current totem pole output stage.
Key Specifications
| Parameter | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Reference Output Voltage | Vref | 4.95 | 5.0 | 5.05 | V |
| Line Regulation | Regline | -2.0 | - | 20 | mV |
| Load Regulation | Regload | -3.0 | - | 25 | mV |
| Temperature Stability | TS | -0.2 | - | - | mV/°C |
| Oscillator Frequency | fosc | 47 | 50 | 52 | kHz |
| Output Voltage High State | VOH | 5.0 | - | 6.2 | V |
| Output Voltage Low State | VOL | 0.8 | - | 1.1 | V |
| Operating Junction Temperature | TJ | - | - | 150 | °C |
| Operating Ambient Temperature | TA | 0 | - | 70 | °C |
Key Features
- Trimmed Oscillator: For precise duty cycle control.
- Current Mode Operation: Up to 500 kHz.
- Automatic Feed Forward Compensation: Enhances stability.
- Latching PWM for Cycle-by-Cycle Current Limiting: Ensures safe operation.
- Internally Trimmed Reference with Undervoltage Lockout: Provides stable reference voltage and protection.
- High Current Totem Pole Output: Ideal for driving power MOSFETs with up to ±1.0 A peak drive current.
- Programmable Output Deadtime and Single Pulse Metering: For customized control and protection.
- Separate Power and Ground Pins for Output Stage (SOIC-14): Reduces switching transient noise.
Applications
The UC3842ADM is designed for various power conversion applications, including:
- Off-Line Converters: Suitable for high-voltage applications with UVLO thresholds of 16 V (on) and 10 V (off).
- DC-to-DC Converters: Ideal for lower voltage applications with UVLO thresholds of 8.5 V (on) and 7.6 V (off) for the UC3843A series.
- Power Supplies: Used in switched-mode power supplies requiring high efficiency and reliability.
- Motor Control and Industrial Power Systems: Where precise current control and high reliability are essential.
Q & A
- What is the primary function of the UC3842ADM?
The UC3842ADM is a high-performance, fixed-frequency, current-mode controller designed for off-line and DC-to-DC converter applications.
- What is the typical oscillator frequency range of the UC3842ADM?
The oscillator frequency typically ranges from 47 kHz to 52 kHz.
- What is the maximum output duty cycle of the UC3842ADM?
The maximum output duty cycle can be programmed using the timing components RT and CT.
- How does the UC3842ADM protect against undervoltage conditions?
The device includes input and reference undervoltage lockouts with hysteresis to protect against undervoltage conditions.
- What is the significance of the totem pole output stage in the UC3842ADM?
The totem pole output stage is designed for direct drive of power MOSFETs, capable of up to ±1.0 A peak drive current.
- How does the SOIC-14 package benefit the design?
The SOIC-14 package provides separate pins for VC (output supply) and Power Ground, reducing switching transient noise and offering added flexibility in tailoring the drive voltage.
- What are the typical operating temperatures for the UC3842ADM?
The operating ambient temperature range is from 0°C to 70°C, and the operating junction temperature should not exceed 150°C.
- How does the current sense comparator work in the UC3842ADM?
The current sense comparator terminates the output switch conduction when the peak inductor current reaches the threshold level established by the Error Amplifier Output/Compensation.
- What are some common applications of the UC3842ADM?
Common applications include off-line converters, DC-to-DC converters, power supplies, and motor control and industrial power systems.
- Is the UC3842ADM available in different packages?
Yes, it is available in an 8-pin dual-in-line plastic package and a 14-pin plastic surface mount (SOIC-14) package.
