Overview
The UC3844BVN 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
| Parameter | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Reference Output Voltage | VREF | 4.90 | 5.00 | 5.10 | V |
| Oscillation Frequency | f | 47 | 52 | 57 | kHz |
| Output Voltage Swing High State | VOH | - | - | 6.2 | V |
| Output Voltage Swing Low State | VOL | 0.8 | - | 1.1 | V |
| UVLO Thresholds | - | 16 V (on), 10 V (off) | - | - | V |
| Output Current - Sink | ISink | 2.0 | - | 12 | mA |
| Output Current - Source | ISource | -1.0 | - | 12 | mA |
Key Features
- Trimmed oscillator for precise frequency control
- Oscillator frequency guaranteed at up to 500 kHz output switching frequency
- Current mode operation
- 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 (UVLO) and hysteresis
- High current totem pole output
- Low startup and operating current
- Pb-free packages available
Applications
The UC3844BVN is designed for various power conversion applications, including:
- Off-Line converters
- DC-DC converters (e.g., boost, flyback regulators)
- Positive output step-up and step-down converters
Q & A
- What is the primary function of the UC3844BVN?
The UC3844BVN is a high-performance fixed frequency current mode controller designed for Off-Line and DC-DC converter applications.
- What are the UVLO thresholds for the UC3844BVN?
The UVLO thresholds for the UC3844BVN are 16 V (on) and 10 V (off).
- What is the typical oscillator frequency of the UC3844BVN?
The typical oscillator frequency is around 52 kHz, but it can be programmed up to 500 kHz output switching frequency.
- What are the key protective features of the UC3844BVN?
The key protective features include input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering).
- What types of packages are available for the UC3844BVN?
The UC3844BVN 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 purpose of the totem pole output in the UC3844BVN?
The totem pole output is designed to drive power MOSFETs efficiently).
- How is the output deadtime adjustable in the UC3844BVN?
The output deadtime can be programmed from 50% to 70% using an internal flip-flop and the discharge period of the capacitor CT).
- What is the significance of the high gain error amplifier in the UC3844BVN?
The high gain error amplifier provides precise control over the output voltage, ensuring stable operation of the converter).
- Can the UC3844BVN operate at 100% duty cycle?
No, the UC3844BVN can operate with a maximum duty cycle of 50%, while the UC3842 and UC3843 can operate at 100% duty cycle).
- What is the typical startup current for the UC3844BVN?
The UC3844BVN has a low startup current, which is a key feature for efficient operation).
