Overview
The UC3844BNG, part of the UC3844B series from onsemi, is a high-performance, fixed-frequency current mode controller. 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 ideal for driving a power MOSFET. The device includes various protective features such as input and reference undervoltage lockouts, cycle-by-cycle current limiting, and adjustable output deadtimes.
Key Specifications
| Characteristic | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Oscillator Frequency | fOSC | - | 250 kHz | - | kHz |
| Output Switching Frequency | - | - | 500 kHz | - | kHz |
| Startup Threshold (UCX844B) | Vth | 15 V | - | 17 V | V |
| Minimum Operating Voltage After Turn-On (UCX844B) | VCC(min) | 9.0 V | - | 11 V | V |
| Output Current - Sink | ISink | 2.0 mA | - | 12 mA | mA |
| Output Current - Source | ISource | -0.5 mA | - | 12 mA | mA |
| Output Voltage Swing High State | VOH | 5.0 V | - | 6.2 V | V |
| Output Voltage Swing Low State | VOL | 0.8 V | - | 1.1 V | V |
| Power Supply Current (Startup) | ICC | - | 0.3 mA | 0.5 mA | mA |
| Power Supply Current (Operating) | ICC | - | 12 mA | 17 mA | mA |
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 UC3844BNG is designed for off-line and DC-DC converter applications. It is particularly suited for power supply designs that require high performance, reliability, and minimal external components. These include:
- Switch-Mode Power Supplies
- DC-DC Converters
- High-Efficiency Power Conversion Systems
- Automotive and Industrial Power Systems
Q & A
- What is the primary function of the UC3844BNG?
The UC3844BNG 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 UC3844BNG?
The oscillator frequency is guaranteed at 250 kHz. - What is the maximum output switching frequency of the UC3844BNG?
The maximum output switching frequency is up to 500 kHz. - How is the output deadtime adjustable?
The output deadtime is adjustable from 50% to 70% using the internal flip-flop and CT discharge period. - What protective features does the UC3844BNG include?
The device includes input and reference undervoltage lockouts, cycle-by-cycle current limiting, and adjustable output deadtimes. - What is the startup threshold voltage for the UCX844B?
The startup threshold voltage for the UCX844B is between 15 V and 17 V. - What is the minimum operating voltage after turn-on for the UCX844B?
The minimum operating voltage after turn-on for the UCX844B is between 9.0 V and 11 V. - Is the UC3844BNG Pb-Free and RoHS Compliant?
Yes, the UC3844BNG is Pb-Free and RoHS Compliant. - What are the typical applications of the UC3844BNG?
The UC3844BNG is typically used in switch-mode power supplies, DC-DC converters, high-efficiency power conversion systems, and automotive and industrial power systems. - How does the UC3844BNG handle current sensing and limiting?
The UC3844BNG operates as a current mode controller, where output switch conduction is initiated by the oscillator and terminated when the peak inductor current reaches the threshold level established by the Error Amplifier Output/Compensation.
