Overview
The UC3845BDR2 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 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. The UC3845BDR2 is available in various package options, including 8-pin dual-in-line and surface mount (SOIC-8 and SOIC-14) packages.
Key Specifications
| Characteristic | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Reference Output Voltage | Vref | 4.95 | 5.0 | 5.05 | V |
| Line Regulation | Regline | - | 2.0 | 20 | mV |
| Load Regulation | Regload | - | 3.0 | 25 | mV |
| Temperature Stability | TS | - | 0.2 | - | mV/°C |
| Output Current - Sink | ISink | 2.0 | -0.5 | 12 | mA |
| Output Current - Source | ISource | 2.0 | -0.5 | 12 | mA |
| Output Voltage Swing High State | VOH | 5.0 | - | 6.2 | V |
| Output Voltage Swing Low State | VOL | 0.8 | - | 1.1 | V |
| Current Sense Input Voltage Gain | AV | 2.85 | 3.0 | 3.15 | V/V |
| Maximum Current Sense Input Threshold | Vth | 0.9 | 1.0 | 1.1 | V |
| Power Supply Rejection Ratio | PSRR | - | 70 | - | dB |
| Propagation Delay (Current Sense Input to Output) | tPLH(In/Out) | 150 | - | 300 | ns |
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
- ESD Protection and Latch-Up Protection
Applications
The UC3845BDR2 is specifically designed for off-line and DC-DC converter applications. It is suitable for a wide range of power supply designs, including:
- Off-line power supplies
- DC-DC converters
- Switch-mode power supplies
- High-efficiency power conversion systems
Q & A
- What is the primary function of the UC3845BDR2?
The UC3845BDR2 is a high-performance fixed frequency current mode controller designed for off-line and DC-DC converter applications.
- What are the key components of the UC3845BDR2?
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.
- What are the UVLO thresholds for the UC3845BDR2?
The UC3845BDR2 has UVLO thresholds of 8.4V (on) and 7.6V (off).
- What is the oscillator frequency of the UC3845BDR2?
The oscillator frequency is guaranteed at 250 kHz.
- How is output deadtime controlled in the UC3845BDR2?
The output deadtime is adjustable from 50% to 70% using an internal flip-flop that blanks the output off every other oscillator cycle.
- What protective features does the UC3845BDR2 include?
The device includes input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering.
- In what packages is the UC3845BDR2 available?
The UC3845BDR2 is available in 8-pin dual-in-line and surface mount (SOIC-8 and SOIC-14) packages.
- Is the UC3845BDR2 Pb-Free and RoHS compliant?
Yes, the UC3845BDR2 is Pb-Free and RoHS compliant.
- What is the power supply rejection ratio (PSRR) of the UC3845BDR2?
The PSRR is 70 dB.
- What is the propagation delay from the current sense input to the output?
The propagation delay is between 150 ns and 300 ns.
