Overview
The UC2845BNG is a high-performance, fixed-frequency current mode controller produced by ON Semiconductor. This integrated circuit is specifically designed for off-line and DC-DC converter applications, offering a cost-effective solution with minimal external components. The UC2845B series features an oscillator, a temperature-compensated reference, a high-gain error amplifier, a current sensing comparator, and a high-current totem pole output stage, making it ideal for driving power MOSFETs.
Key Specifications
| Characteristic | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Oscillator Frequency | fOSC | - | 250 kHz | - | kHz |
| Output Switching Frequency | - | - | 500 kHz | - | kHz |
| Reference Output Voltage | Vref | 4.95 | 5.0 | 5.05 | V |
| Input Undervoltage Lockout (On/Off) | Vth | 8.4 / 7.6 | - | - | V |
| Minimum Operating Voltage After Turn-On | VCC(min) | 7.6 | - | 8.2 | V |
| Output Current (Source/Sink) | IO | - | - | 1.0 A | A |
| Output Voltage Rise/Fall Time (CL = 1.0 nF) | tr/tf | 50 | - | 150 | ns |
| Operating Junction Temperature | TJ | -25 | - | 85 | °C |
Key Features
- Trimmed Oscillator for Precise Frequency Control
- Current Mode Operation 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
- Input and Reference Undervoltage Lockouts with Hysteresis
- Low Startup and Operating Current
- Pb-Free and RoHS Compliant Packages
Applications
The UC2845BNG is designed for use in off-line and DC-DC converter applications. It is particularly suited for:
- Off-line power supplies
- DC-DC converters
- Switch-mode power supplies
- High-efficiency power conversion systems
Q & A
- What is the primary function of the UC2845BNG?
The UC2845BNG is a high-performance, fixed-frequency current mode controller designed for off-line and DC-DC converter applications.
- What is the typical oscillator frequency of the UC2845BNG?
The oscillator frequency is typically 250 kHz.
- What are the undervoltage lockout thresholds for the UC2845BNG?
The input undervoltage lockout thresholds are 8.4 V (on) and 7.6 V (off).
- What is the maximum output current of the UC2845BNG?
The maximum output current is 1.0 A (source or sink).
- What is the operating junction temperature range for the UC2845BNG?
The operating junction temperature range is from -25°C to 85°C.
- Does the UC2845BNG have protective features?
Yes, it includes protective features such as input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering.
- What type of output stage does the UC2845BNG have?
The UC2845BNG has a high-current totem pole output stage designed for direct drive of power MOSFETs.
- Is the UC2845BNG Pb-Free and RoHS compliant?
Yes, the UC2845BNG is Pb-Free and RoHS compliant.
- What are the typical rise and fall times of the output voltage?
The typical rise and fall times of the output voltage are 50 ns with a 1.0 nF load.
- What is the purpose of the internal flip-flop in the UC2845BNG?
The internal flip-flop blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed from 50% to 70%.
