Overview
The UC3845DR2G is a high-performance, fixed-frequency, current-mode PWM controller produced by ON Semiconductor. It is specifically designed for off-line and DC-to-DC converter applications, offering a cost-effective solution with minimal external components. This controller features a trimmed oscillator, a temperature-compensated reference, a high-gain error amplifier, a current sensing comparator, and a high-current totem pole output stage ideal for driving power MOSFETs.
Key Specifications
| Parameter | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Supply Voltage | VCC | - | - | 30 | V |
| Output Current, Source or Sink | IO | - | - | 1.0 | A |
| Output Energy (Capacitive Load per Cycle) | - | - | - | 5.0 | mJ |
| Error Amp Output Sink Current | ISink | - | - | 10 | mA |
| Power Dissipation at TA ≤ 25°C (14SOP) | PD | - | - | 680 | mW |
| Storage Temperature Range | TSTG | -65 | - | 150 | °C |
| Operating Ambient Temperature | TA | 0 | - | 70 | °C |
| UVLO Startup Threshold | Vth | 8.4 | - | 9.0 | V |
| UVLO Minimum Operating Voltage After Turn-On | VCC(min) | 7.6 | - | 8.2 | V |
| Output Switching Frequency | - | - | - | 500 kHz | - |
Key Features
- Current Mode Operation up 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 for driving power MOSFETs
- Input Undervoltage Lockout with Hysteresis
- Low Startup and Operating Current
- Direct Interface with ON Semiconductor SENSEFET Products
- Pb-Free Packages are Available
Applications
The UC3845DR2G is specifically designed for off-line and DC-to-DC converter applications. It is ideal for use in:
- Off-line converters, particularly where efficient bootstrap startup techniques are required.
- Lower voltage DC-to-DC converter applications.
- Power supplies requiring high efficiency and reliability.
- Switch-mode power supplies where precise duty cycle control and current limiting are necessary.
Q & A
- What is the maximum output current of the UC3845DR2G?
The maximum output current of the UC3845DR2G is ±1.0 A peak drive current.
- What are the UVLO thresholds for the UC3845DR2G?
The UVLO thresholds for the UC3845DR2G are 8.4 V (on) and 7.6 V (off).
- What is the maximum operating frequency of the UC3845DR2G?
The maximum operating frequency of the UC3845DR2G is up to 500 kHz.
- What types of packages are available for the UC3845DR2G?
The UC3845DR2G is available in an 8-pin dual-in-line plastic package and a 14-pin plastic surface mount (SOIC-14) package.
- What is the purpose of the separate power and ground pins in the SOIC-14 package?
The separate power and ground pins in the SOIC-14 package help reduce the effects of switching transient noise on the control circuitry.
- What are the key protective features of the UC3845DR2G?
The key protective features include input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering.
- How does the UC3845DR2G handle output deadtime?
The UC3845DR2G allows output deadtime to be programmed from 50% to 70% using a flip-flop that blanks the output off every other oscillator cycle.
- What is the typical rise and fall time of the output voltage with a 1.0 nF load?
The typical rise and fall time of the output voltage with a 1.0 nF load is 50 ns.
- Is the UC3845DR2G Pb-free?
- What is the storage temperature range for the UC3845DR2G?
The storage temperature range for the UC3845DR2G is -65°C to +150°C.
