Overview
The UC3843BVDR2G is a high-performance fixed frequency current mode controller produced by onsemi. This integrated circuit is specifically designed for off-line and DC-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, a current sensing comparator, and a high current totem pole output suitable for driving power MOSFETs.
Key Specifications
| Characteristics | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Reference Output Voltage (IO = 1.0 mA, TJ = 25°C) | Vref | 4.95 | 5.0 | 5.05 | V |
| Line Regulation (VCC = 12 V to 25 V) | Regline | - | 2.0 | 20 | mV |
| Load Regulation (IO = 1.0 mA to 20 mA) | Regload | - | 3.0 | 25 | mV |
| Output Current, Source or Sink | IO | - | - | 1.0 | A |
| Output Voltage Low State (ISink = 20 mA) | VOL | - | 0.1 | 1.6 | V |
| Output Voltage High State (ISource = 20 mA) | VOH | - | 12 | 13.5 | V |
| Current Sense Input Voltage Gain | AV | 2.85 | 3.0 | 3.15 | V/V |
| Maximum Current Sense Input Threshold | Vth | 0.9 | 1.0 | 1.1 | V |
| Power Supply Rejection Ratio (VCC = 12 V to 25 V) | PSRR | - | 70 | - | dB |
Key Features
- Trimmed Oscillator for Precise Frequency Control: The oscillator frequency is programmable using external timing components RT and CT, ensuring precise duty cycle control.
- Current Mode Operation: Supports operation up to 500 kHz, making it suitable for a wide range of applications.
- Automatic Feed Forward Compensation: Enhances stability and performance of the converter.
- Latching PWM for Cycle-by-Cycle Current Limiting: Ensures robust current limiting and prevents overcurrent conditions.
- Internally Trimmed Reference with Undervoltage Lockout: Features a temperature-compensated reference and undervoltage lockouts with hysteresis to ensure stable operation.
- High Current Totem Pole Output: Suitable for driving power MOSFETs with high current capability.
- Protective Features: Includes input and reference undervoltage lockouts, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering.
- Low Startup and Operating Current: Minimizes power consumption during startup and operation.
- Pb-Free and Halide-Free Device: Compliant with environmental regulations.
Applications
The UC3843BVDR2G is designed for off-line and DC-DC converter applications. It is particularly useful in:
- Switch-Mode Power Supplies: Including flyback, forward, and half-bridge converters.
- DC-DC Converters: Suitable for buck, boost, and buck-boost topologies.
- Power Factor Correction (PFC) Circuits: Helps in achieving high power factor and efficient power conversion.
Q & A
- What is the typical oscillator frequency of the UC3843BVDR2G?
The oscillator frequency is programmable but guaranteed at 250 kHz for specific configurations.
- What are the undervoltage lockout thresholds for the UC3843BVDR2G?
The UC3843BVDR2G has undervoltage lockout thresholds of 8.5 V (on) and 7.6 V (off).
- What is the maximum output current of the UC3843BVDR2G?
The maximum output current is 1.0 A.
- What are the package options available for the UC3843BVDR2G?
It is available in SOIC-8 and SOIC-14 packages.
- Does the UC3843BVDR2G have built-in protective features?
Yes, it includes input and reference undervoltage lockouts, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering.
- What is the power supply rejection ratio (PSRR) of the UC3843BVDR2G?
The PSRR is typically 70 dB.
- How does the current sense comparator work in the UC3843BVDR2G?
The current sense comparator terminates the output switch conduction when the peak inductor current reaches the threshold level established by the error amplifier output.
- Is the UC3843BVDR2G Pb-Free and Halide-Free?
Yes, it is compliant with environmental regulations and is Pb-Free and Halide-Free.
- What is the typical DC voltage gain of the error amplifier in the UC3843BVDR2G?
The error amplifier has a typical DC voltage gain of 90 dB.
- How does the oscillator configuration work in the UC3843BVDR2G?
The oscillator frequency is programmed by the values chosen for the timing components RT and CT, with the capacitor CT getting charged from the Vref source through resistor RT.
