Overview
The UC3842DG4 is a fixed-frequency current-mode PWM (Pulse Width Modulation) controller produced by Texas Instruments. This integrated circuit is specifically designed for off-line and DC-to-DC converter applications, requiring minimal external components. It 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 for driving power MOSFETs.
Key Specifications
| Parameter | Symbol | Min. | Typ. | Max. | Unit |
|---|---|---|---|---|---|
| Supply Voltage | VCC | - | - | 30 | V |
| Output Current | IO | - | - | ±1 | A |
| Analog Inputs (Pin 2, 3) | V(ANA) | -0.3 | - | 6.3 | V |
| Error Amp Output Sink Current | ISINK (E.A) | - | - | 10 | mA |
| Reference Output Voltage | VREF | 4.90 | 5.00 | 5.10 | V |
| Oscillation Frequency | fOSC | 47 | 52 | 57 | kHz |
| UVLO Start Threshold | VTH(ST) | 14.5 | 16.0 | 17.5 | V |
| UVLO Off Threshold | VCCOFF | 8.5 | 10.0 | 11.5 | V |
| Maximum Duty Cycle | D(MAX) | 95 | 97 | 100 | % |
| Start-Up Current | IST | - | - | 1 | mA |
| Operating Supply Current | ICC(OPR) | - | - | 17 | mA |
Key Features
- Low Start-Up Current: Less than 1 mA, making it energy-efficient during startup.
- Maximum Duty Clamp: Ensures controlled duty cycles, with the UC3842 and UC3843 capable of 100% duty cycle and UC3844 and UC3845 capable of up to 50% duty cycle.
- Under-Voltage Lockout (UVLO) with Hysteresis: Provides protection against low input voltages with defined start and off thresholds.
- Operating Frequency up to 500 kHz: Allows for high-frequency switching applications.
- Temperature Compensated Reference: Ensures stable operation over a range of temperatures.
- High Gain Error Amplifier: Enhances the accuracy of feedback control.
- Current Sensing Comparator: Enables pulse-by-pulse current limiting.
- High Current Totem Pole Output: Suitable for driving power MOSFETs.
- Automatic Feed Forward Compensation: Improves load response characteristics.
Applications
The UC3842DG4 is optimized for use in off-line and DC-to-DC converter applications. It is particularly suitable for:
- Switch-mode power supplies.
- DC-DC converters.
- High-frequency switching power supplies.
- Power management systems requiring precise control and high efficiency.
Q & A
- What is the typical operating frequency of the UC3842DG4?
The typical operating frequency is around 52 kHz, with a range of 47 kHz to 57 kHz.
- What is the maximum duty cycle for the UC3842DG4?
The maximum duty cycle for the UC3842DG4 is up to 100%.
- What is the UVLO start threshold for the UC3842DG4?
The UVLO start threshold is between 14.5V and 17.5V.
- What is the operating supply current for the UC3842DG4?
The operating supply current is typically around 17 mA.
- What are the key features of the UC3842DG4?
Key features include low start-up current, maximum duty clamp, UVLO with hysteresis, high operating frequency, and a temperature-compensated reference.
- What types of applications is the UC3842DG4 suitable for?
The UC3842DG4 is suitable for off-line and DC-to-DC converter applications, including switch-mode power supplies and high-frequency switching power supplies.
- What is the storage temperature range for the UC3842DG4?
The storage temperature range is from -65°C to +150°C.
- What is the maximum output current of the UC3842DG4?
The maximum output current is ±1 A.
- How does the UC3842DG4 protect against low input voltages?
The UC3842DG4 features an under-voltage lockout (UVLO) with hysteresis to protect against low input voltages.
- What is the typical reference output voltage of the UC3842DG4?
The typical reference output voltage is 5.00 V, with a range of 4.90 V to 5.10 V.
