Overview
The UC3842D, produced by Unitrode (now part of Texas Instruments), is a fixed-frequency current-mode Pulse Width Modulator (PWM) controller. This integrated circuit is specifically designed for off-line and DC to DC converter applications, offering a balance between good electrical performance and low cost. The UC3842D is part of the UC3842/UC3843/UC3844/UC3845 family, which provides designers with an inexpensive controller for achieving the performance advantages of current-mode operation.
Key Specifications
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Supply Voltage | VCC | 30 | V |
| Output Current | IO | ±1 | A |
| Analog Inputs (Pin 2, 3) | V(ANA) | -0.3 to 6.3 | V |
| Error Amp Output Sink Current | ISINK (E.A) | 10 | mA |
| Power Dissipation at TA≤25°C (8DIP) | PD | 1200 | mW |
| Storage Temperature Range | TSTG | -65 ~ +150 | °C |
| Reference Output Voltage | VREF | 4.90 to 5.10 | V |
| Oscillation Frequency | f | 47 to 57 kHz | kHz |
Key Features
- Low Start-up Current: The UC3842D has a low start-up current, making it energy-efficient.
- Maximum Duty Clamp: The UC3842D can operate with a maximum duty cycle of approximately 100%, while the UC3844 and UC3845 are clamped to 50% maximum duty cycle.
- UVLO With Hysteresis: The device features Under-Voltage Lockout (UVLO) with hysteresis, ensuring stable operation. For UC3842D, the UVLO thresholds are 16V (on) and 10V (off).
- Operating Frequency up to 500KHz: The oscillator frequency can be programmed up to 500 kHz, providing flexibility in design.
- Temperature Compensated Reference: The device includes a temperature-compensated reference voltage for stable operation across various temperatures.
- High Gain Error Amplifier: A high-gain error amplifier is integrated for precise control.
- Current Sensing Comparator: The UC3842D includes a current sensing comparator for external current-to-voltage conversion.
- High Current Totem-Pole Output: The device has a high current totem-pole output for driving power MOSFETs or transistors.
Applications
The UC3842D is specifically designed for off-line and DC to DC converter applications. It is optimized for efficient power sequencing of off-line converters, DC to DC regulators, and for driving power MOSFETs or transistors. This makes it suitable for a wide range of power supply designs, including switch-mode power supplies, DC-DC converters, and other power management systems.
Q & A
- What is the primary function of the UC3842D?
The UC3842D is a fixed-frequency current-mode Pulse Width Modulator (PWM) controller designed for off-line and DC to DC converter applications.
- What is the maximum supply voltage for the UC3842D?
The maximum supply voltage (VCC) for the UC3842D is 30V.
- What is the maximum duty cycle for the UC3842D?
The UC3842D can operate with a maximum duty cycle of approximately 100%.
- What are the UVLO thresholds for the UC3842D?
The UVLO thresholds for the UC3842D are 16V (on) and 10V (off).
- What is the typical oscillation frequency range for the UC3842D?
The typical oscillation frequency range for the UC3842D is between 47 kHz and 57 kHz.
- Can the UC3842D be used for high-frequency applications?
Yes, the oscillator frequency can be programmed up to 500 kHz, making it suitable for high-frequency applications.
- What type of output does the UC3842D have for driving power devices?
The UC3842D has a high current totem-pole output for driving power MOSFETs or transistors.
- How does the UC3842D handle current sensing?
The UC3842D handles current sensing through an external current-to-voltage conversion using a ground-referenced resistor Rs.
- What are some common applications of the UC3842D?
The UC3842D is commonly used in off-line converters, DC to DC regulators, and other power management systems.
- What is the significance of the UVLO feature in the UC3842D?
The UVLO (Under-Voltage Lockout) feature ensures that the device operates only when the supply voltage is within a safe range, preventing damage and ensuring stable operation.
