Overview
The UC3844BDR2, produced by 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, making it ideal for driving a power MOSFET. The device includes protective features such as input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering. It is available in 8-pin dual-in-line and surface mount (SOIC-8) packages, as well as a 14-pin surface mount (SOIC-14) package with separate power and ground pins for the totem pole output stage.
Key Specifications
| Characteristic | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Oscillator Frequency | fOSC | - | 250 kHz | - | kHz |
| Output Switching Frequency | fSW | - | - | 500 kHz | kHz |
| Output Deadtime Adjustable | - | 50% | - | 70% | % |
| Undervoltage Lockout (VCC) | UVLO | 10 V | - | 16 V | V |
| Output Voltage High State | VOH | 5.0 V | - | 6.2 V | V |
| Output Voltage Low State | VOL | 0.8 V | - | 1.1 V | V |
| Current Sense Input Voltage Gain | AV | 2.85 V/V | - | 3.15 V/V | V/V |
| Maximum Current Sense Input Threshold | Vth | 0.9 V | - | 1.1 V | V |
| Power Supply Rejection Ratio | PSRR | - | - | 70 dB | dB |
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 UC3844BDR2 is specifically designed for off-line and dc-dc converter applications. It is suitable for a variety of power supply designs, including switch-mode power supplies, DC-DC converters, and other high-performance power management systems. Its features make it an ideal choice for applications requiring precise frequency control, high current output, and robust protective features.
Q & A
- What is the primary function of the UC3844BDR2?
The UC3844BDR2 is a high-performance fixed frequency current mode controller designed for off-line and dc-dc converter applications.
- What are the typical oscillator frequencies for the UC3844BDR2?
The oscillator frequency is guaranteed at 250 kHz, and the output switching frequency can go up to 500 kHz.
- How is the output deadtime adjustable on the UC3844BDR2?
The output deadtime can be programmed from 50% to 70% using the oscillator and discharge periods.
- What are the undervoltage lockout thresholds for the UC3844BDR2?
The undervoltage lockout thresholds are 16 V (on) and 10 V (off) for the UCX844B, and 8.5 V (on) and 7.6 V (off) for the UCX845B.
- What type of output does the UC3844BDR2 have?
The UC3844BDR2 has a high current totem pole output, suitable for driving a power MOSFET.
- What are the available package types for the UC3844BDR2?
The device is available in 8-pin dual-in-line and surface mount (SOIC-8) packages, as well as a 14-pin surface mount (SOIC-14) package.
- Does the UC3844BDR2 have any 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 UC3844BDR2 Pb-Free and RoHS compliant?
Yes, the UC3844BDR2 is Pb-Free and RoHS compliant.
- What is the power supply rejection ratio (PSRR) of the UC3844BDR2?
The power supply rejection ratio (PSRR) is 70 dB.
- How does the current sense input voltage gain work on the UC3844BDR2?
The current sense input voltage gain is between 2.85 V/V and 3.15 V/V.
