Overview
The UC2845BD1R2 is a high-performance fixed frequency current mode controller produced by onsemi. It is specifically designed for off-line and dc-dc converter applications, offering a cost-effective solution with minimal external components. This integrated circuit features an oscillator, a temperature-compensated reference, a high-gain error amplifier, a current sensing comparator, and a high-current totem pole output, making it ideal 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 | ||
| Output Energy (Capacitive Load per Cycle) | W | 5.0 | μJ | ||
| Current Sense and Voltage Feedback Inputs | Vin | -0.3 | 5.5 | V | |
| Reference Output Voltage | Vref | 4.95 | 5.0 | 5.05 | V |
| Oscillator Frequency | 250 | kHz | |||
| Operating Ambient Temperature | TA | -25 | 85 | °C | |
| Startup Threshold (UC2845B) | 8.5 | V | |||
| Shutdown Threshold (UC2845B) | 7.6 | V |
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
- Available in 8-pin DIP and SOIC-8, and 14-pin SOIC-14 packages
Applications
The UC2845BD1R2 is designed for use in off-line and dc-dc converter applications. It is particularly suited for power supply designs that require high efficiency, reliability, and minimal external components. Common applications include:
- Switch Mode Power Supplies
- DC-DC Converters
- Offline Power Supplies
- High-Efficiency Power Conversion Systems
Q & A
- What is the primary function of the UC2845BD1R2?
The UC2845BD1R2 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 UC2845BD1R2?
The oscillator frequency is guaranteed at 250 kHz.
- What are the undervoltage lockout (UVLO) thresholds for the UC2845B?
The UVLO thresholds are 8.5 V (on) and 7.6 V (off).
- What is the maximum output current of the UC2845BD1R2?
The maximum output current is 1.0 A.
- What are the available package types for the UC2845BD1R2?
The device is available in 8-pin DIP and SOIC-8, and 14-pin SOIC-14 packages.
- Does the UC2845BD1R2 have protective features?
Yes, it includes input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering.
- Is the UC2845BD1R2 RoHS compliant?
Yes, the device is Pb-Free and RoHS compliant.
- What is the operating ambient temperature range for the UC2845BD1R2?
The operating ambient temperature range is -25°C to 85°C.
- How is the output deadtime adjustable?
The output deadtime can be programmed from 50% to 70% using a flip-flop that blanks the output off every other oscillator cycle.
- What is the purpose of the high-gain error amplifier in the UC2845BD1R2?
The high-gain error amplifier is used to control the peak inductor current on a cycle-by-cycle basis.
