Overview
The UC3844BVNG is a high-performance fixed frequency current mode controller produced by onsemi. It is part of the UC3844B and UC3845B series, which are specifically designed for Off-Line and DC-DC converter applications. These integrated circuits offer a cost-effective solution with minimal external components, making them ideal for a variety of power management needs.
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. This configuration is well-suited for driving power MOSFETs and includes several 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 |
| Output Deadtime Adjustable | - | 50% to 70% | - | - | % |
| UVLO Thresholds (UC3844B) | VCC | 10 V | - | 16 V | V |
| UVLO Thresholds (UC3845B) | VCC | 7.6 V | - | 8.5 V | V |
| Output Voltage High State | VOH | 12 V | - | 13.5 V | V |
| Output Voltage Low State | VOL | 0.1 V | - | 1.6 V | V |
| Output Current Sink/Source | ISink/ISource | - | - | 1.0 A | A |
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 Packages are Available
Applications
The UC3844BVNG is designed for Off-Line and DC-DC converter applications. It is particularly useful in:
- Boost, Flyback, and other DC-DC converter configurations
- Isolation capable output step-up and step-up converters
- Power supply systems requiring high efficiency and reliability
- Automotive and industrial power management systems
Q & A
- What is the primary function of the UC3844BVNG?
The UC3844BVNG 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 UC3844BVNG?
The oscillator frequency is guaranteed at 250 kHz.
- What are the UVLO thresholds for the UC3844B and UC3845B?
The UC3844B has UVLO thresholds of 16 V (on) and 10 V (off), while the UC3845B has thresholds of 8.5 V (on) and 7.6 V (off).
- What is the maximum output switching frequency of the UC3844BVNG?
The maximum output switching frequency is up to 500 kHz.
- What protective features are included in the UC3844BVNG?
The device includes input and reference undervoltage lockouts, cycle-by-cycle current limiting, and a latch for single pulse metering.
- What is the output deadtime adjustment range of the UC3844BVNG?
The output deadtime can be adjusted from 50% to 70%.
- What type of output stage does the UC3844BVNG have?
The device features a high current totem pole output stage.
- Is the UC3844BVNG available in Pb-Free packages?
Yes, the UC3844BVNG is available in Pb-Free packages and is RoHS compliant.
- What are the typical package options for the UC3844BVNG?
The device is available in 8-pin dual-in-line and surface mount (SO-8) packages, as well as a 14-pin surface mount (SO-14) package.
- What is the significance of the separate power and ground pins in the SO-14 package?
The separate power and ground pins in the SO-14 package help reduce the effects of switching transient noise on the control circuitry.
