Overview
The UC3845BDR2G is a high-performance fixed frequency current mode controller produced by onsemi. It is part of the UC3845B series, which is specifically designed for off-line and DC-DC converter applications. This integrated circuit offers a cost-effective solution with minimal external components, making it ideal for a variety of power supply designs. The UC3845BDR2G features an oscillator, a temperature-compensated reference, a high-gain error amplifier, a current sensing comparator, and a high-current totem pole output stage suitable for driving power MOSFETs.
Key Specifications
| Characteristic | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Bias and Driver Voltages | VCC, VC | - | - | 36 | V |
| Total Power Supply and Zener Current | ICC + IZ | - | - | 30 | mA |
| Output Current, Source or Sink | IO | - | - | 1.0 | A |
| Oscillator Frequency | fOSC | - | 250 kHz | - | kHz |
| Output Deadtime Adjustable | - | 50% to 70% | - | - | % |
| Undervoltage Lockout Thresholds | Vth | 8.4 V (on), 7.6 V (off) | - | - | V |
| Minimum Operating Voltage After Turn-On | VCC(min) | 8.2 | - | - | V |
| Output Voltage Rise/Fall Time (CL = 1.0 nF) | tr/tf | 50 | - | 150 | ns |
Key Features
- Trimmed Oscillator for Precise Frequency Control
- Current Mode Operation up to 500 kHz Output Switching Frequency
- Output Deadtime Adjustable from 50% to 70%
- Automatic Feed Forward Compensation
- Latching PWM for Cycle-By-Cycle Current Limiting
- Internally Trimmed Reference with Undervoltage Lockout
- High Current Totem Pole Output
- Undervoltage Lockout with Hysteresis
- Low Startup and Operating Current
- Pb-Free and RoHS Compliant
Applications
The UC3845BDR2G is designed for off-line and DC-DC converter applications. It is particularly suited for:
- Switch Mode Power Supplies
- DC-DC Converters
- High-Efficiency Power Conversion Systems
- Industrial Power Supplies
- Automotive and Other Applications Requiring High Reliability
Q & A
- What is the primary function of the UC3845BDR2G?
The UC3845BDR2G is a high-performance fixed frequency current mode controller designed for off-line and DC-DC converter applications.
- What is the oscillator frequency of the UC3845BDR2G?
The oscillator frequency is guaranteed at 250 kHz.
- How is the output deadtime adjustable?
The output deadtime is adjustable from 50% to 70%.
- What are the undervoltage lockout thresholds for the UC3845BDR2G?
The undervoltage lockout thresholds are 8.4 V (on) and 7.6 V (off).
- What is the minimum operating voltage after turn-on for the UC3845BDR2G?
The minimum operating voltage after turn-on is 8.2 V.
- What is the output current capability of the UC3845BDR2G?
The output current capability is up to ±1.0 A peak drive current.
- Is the UC3845BDR2G Pb-Free and RoHS Compliant?
Yes, the UC3845BDR2G is Pb-Free and RoHS Compliant.
- What types of applications is the UC3845BDR2G suited for?
The UC3845BDR2G is suited for switch mode power supplies, DC-DC converters, high-efficiency power conversion systems, industrial power supplies, and automotive applications.
- How does the UC3845BDR2G handle cycle-by-cycle current limiting?
The UC3845BDR2G uses a latching PWM for cycle-by-cycle current limiting.
- What is the purpose of the internal flip-flop in the UC3845BDR2G?
The internal flip-flop blanks the output off every other oscillator cycle, allowing for adjustable output deadtimes.
