Overview
The UC2845BD1G is a high-performance, fixed-frequency current mode controller produced by onsemi. It is part of the UC2845B 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 device features an oscillator, a temperature-compensated reference, a high-gain error amplifier, a current sensing comparator, and a high-current totem pole output stage. These components are optimized for driving power MOSFETs and provide robust protective features such as input and reference undervoltage lockouts, cycle-by-cycle current limiting, and adjustable output deadtime.
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 |
| Output Energy (Capacitive Load per Cycle) | W | - | - | 5.0 | μJ |
| Reference Output Voltage | Vref | 4.95 | 5.0 | 5.05 | V |
| Oscillator Frequency | fOSC | - | 250 kHz | - | kHz |
| Startup Threshold | Vth | 8.4 | - | 9.0 | V |
| Minimum Operating Voltage After Turn-On | VCC(min) | 7.6 | - | 8.2 | V |
| Output Voltage Rise Time | tr | 50 | - | 150 | ns |
| Output Voltage Fall Time | tf | 50 | - | 150 | ns |
Key Features
- Trimmed Oscillator for Precise Frequency Control
- Oscillator Frequency Guaranteed at 250 kHz
- 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
- Undervoltage Lockout with Hysteresis
- Low Startup and Operating Current
- Pb-Free and RoHS Compliant
Applications
The UC2845BD1G is designed for use in 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 and consumer electronics requiring reliable and efficient power management
Q & A
- What is the primary function of the UC2845BD1G?
The UC2845BD1G 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 UC2845BD1G?
The oscillator frequency is guaranteed at 250 kHz.
- What are the undervoltage lockout thresholds for the UC2845BD1G?
The undervoltage lockout thresholds are 8.4V (on) and 7.6V (off).
- What is the maximum output current of the UC2845BD1G?
The maximum output current is 1.0 A.
- What is the purpose of the internal flip-flop in the UC2845BD1G?
The internal flip-flop blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed from 50% to 70%.
- What type of output stage does the UC2845BD1G have?
The device has a high-current totem pole output stage designed for direct drive of power MOSFETs.
- Is the UC2845BD1G Pb-Free and RoHS compliant?
Yes, the UC2845BD1G is Pb-Free and RoHS compliant.
- What are the typical rise and fall times of the output voltage?
The typical rise and fall times are 50 ns with a 1.0 nF load.
- How does the undervoltage lockout protect the device?
The undervoltage lockout ensures the device is fully functional before enabling the output stage, with built-in hysteresis to prevent erratic behavior.
- What is the minimum operating voltage after turn-on for the UC2845BD1G?
The minimum operating voltage after turn-on is 8.2 V.
