Overview
The UC2845BD1 is a high-performance current mode PWM (Pulse Width Modulation) controller produced by STMicroelectronics. This IC is part of the UC284xB family, which is designed to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. The UC2845BD1 is particularly suited for applications requiring precise frequency control and high current handling capabilities.
Key Specifications
| Parameter | Unit | Min. | Typ. | Max. |
|---|---|---|---|---|
| Supply Voltage (Vi) | V | - | - | 30 |
| Output Current (IO) | A | - | - | ±1 |
| Output Energy (EO) | µJ | - | - | 5 |
| Reference Output Voltage (VREF) | V | 4.90 | 5.00 | 5.10 |
| Under-Voltage Lockout (UVLO) Start Threshold | V | 7.8 | 8.4 | 9.0 |
| Minimum Operating Voltage After Turn-on | V | 7.0 | 7.6 | 8.2 |
| Maximum Duty Cycle | % | 47 | 48 | 50 |
| Start-up Current (Ist) | mA | 0.3 | 0.5 | - |
| Operating Supply Current (Ii) | mA | 12 | 17 | - |
| Storage Temperature Range (Tstg) | °C | -65 | - | 150 |
| Junction Operating Temperature (TJ) | °C | -40 | - | 150 |
Key Features
- Trimmed Oscillator: Provides precise frequency control up to 500 kHz.
- Current Mode Operation: Supports current mode control schemes.
- Automatic Feed Forward Compensation: Enhances stability and performance.
- Latching PWM for Cycle-by-Cycle Current Limiting: Ensures safe operation by limiting current on a cycle-by-cycle basis.
- Internally Trimmed Reference with Under-Voltage Lockout (UVLO): Includes UVLO with hysteresis to prevent startup issues.
- High Current Totem Pole Output: Capable of sourcing or sinking high peak currents up to 1 A.
- Low Start-Up and Operating Current: Minimizes power consumption during startup and operation.
- Programmable Oscillator Frequency and Duty Cycle: Allows for customization using external resistors and capacitors.
Applications
- Off-Line Power Supplies: Suitable for high-performance off-line power supply designs.
- DC to DC Converters: Ideal for fixed frequency current mode DC to DC conversion applications.
- Switch Mode Power Supplies: Used in various switch mode power supply configurations requiring precise control and high current handling.
- Industrial Power Systems: Applicable in industrial power systems that demand reliable and efficient power management.
Q & A
- What is the maximum supply voltage for the UC2845BD1?
The maximum supply voltage (Vi) is 30 V.
- What is the typical output current capability of the UC2845BD1?
The output can source or sink up to 1 A of peak current.
- What is the purpose of the under-voltage lockout (UVLO) feature?
The UVLO feature prevents the IC from starting up at low voltages and includes hysteresis to avoid oscillations.
- How is the oscillator frequency programmed in the UC2845BD1?
The oscillator frequency is programmed by connecting a resistor (RT) to Vref and a capacitor (CT) to ground.
- What is the maximum duty cycle for the UC2845BD1?
The maximum duty cycle is 50% for the UC2845BD1.
- What is the typical operating supply current for the UC2845BD1?
The typical operating supply current (Ii) is 17 mA.
- What is the storage temperature range for the UC2845BD1?
The storage temperature range (Tstg) is from -65°C to 150°C.
- Can the UC2845BD1 be used in high-frequency applications?
Yes, the UC2845BD1 can operate up to frequencies of 500 kHz.
- How does the automatic feed forward compensation enhance the performance of the UC2845BD1?
The automatic feed forward compensation improves stability and performance by compensating for variations in the control loop.
- What type of output stage does the UC2845BD1 have?
The UC2845BD1 has a high current totem pole output stage suitable for driving N-Channel MOSFETs.
