Overview
The UC3843DG4 is a high-performance, fixed-frequency, current-mode PWM controller produced by Texas Instruments. It is part of the UCx84x family of control integrated circuits designed to implement off-line and DC-to-DC fixed-frequency current-mode control schemes with a minimal number of external components. This device is optimized for various power supply applications, offering features such as low start-up current, automatic feedforward compensation, and enhanced load-response characteristics.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| VCC (Low impedance source) | - | - | 30 | V |
| IVCC (Self Limiting) | - | - | 30 mA | mA |
| VFB and VISENSE (Analog input voltage) | -0.3 | - | 6.3 | V |
| IOUTPUT (Output drive current) | - | - | ±1 A | A |
| ICOMP (Error amplifier output sink current) | - | - | 10 mA | mA |
| TJ (Junction temperature) | - | - | 150 °C | °C |
| Tstg (Storage temperature) | -65 | - | 150 °C | °C |
| fOSC (Oscillator frequency) | 100 | - | 500 kHz | kHz |
| TA (Operating free-air temperature) | 0 | - | 70 °C | °C |
| VVREF (Reference voltage) | 4.9 | 5 | 5.1 | V |
| VCCON (UVLO enable threshold) | 14.5 | 16 | 17.5 | V |
| VCCOFF (UVLO off threshold) | 8.5 | 10 | 11.5 | V |
| DMAX (Maximum duty cycle) | 47% | 48% | 50% | % |
Key Features
- Optimized for off-line and DC-to-DC converters
- 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
- Up to 500-kHz operation
- Error amplifier with low output resistance
Applications
- Switching regulators of any polarity
- Transformer-coupled DC-DC converters
- Off-line power supplies
- DC-DC converter applications
Q & A
- What is the operating temperature range for the UC3843DG4?
The UC3843DG4 operates from 0°C to 70°C.
- What is the maximum duty cycle for the UC3843DG4?
The maximum duty cycle for the UC3843DG4 is up to 50%.
- What is the purpose of the undervoltage lockout (UVLO) in the UC3843DG4?
The UVLO ensures that the IC is fully functional before the output stage is enabled, preventing erratic output behavior by monitoring the power supply and reference voltage with built-in hysteresis.
- How is the oscillator frequency programmed in the UC3843DG4?
The oscillator frequency is programmed by the values selected for the timing components RT and CT.
- What is the function of the error amplifier in the UC3843DG4?
The error amplifier controls the power converter voltage-feedback loop for stability and has low output resistance.
- What type of output stage does the UC3843DG4 have?
The UC3843DG4 has a high-current totem-pole output stage designed to source or sink high-peak current, suitable for driving N-channel MOSFETs.
- What is the reference voltage for the UC3843DG4?
The reference voltage for the UC3843DG4 is 4.9 to 5.1 V.
- How does the current sense comparator work in the UC3843DG4?
The current sense comparator terminates the output switch conduction when the peak inductor current reaches the threshold level established by the error amplifier output, ensuring cycle-by-cycle control of the inductor current.
- What are the package options available for the UC3843DG4?
The UC3843DG4 is available in SOIC, PDIP, and CFP packages.
- What is the maximum junction temperature for the UC3843DG4?
The maximum junction temperature for the UC3843DG4 is 150 °C.
