Overview
The UC3845BVN 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. The device includes protective features such as input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and adjustable output deadtime.
Key Specifications
| Parameter | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Supply Voltage | VCC | - | - | 36 | V |
| Output Current | IO | - | - | 1.0 | A |
| Reference Output Voltage | VREF | 4.90 | 5.00 | 5.10 | V |
| Oscillation Frequency | f | 47 | 52 | 57 | kHz |
| Output Voltage Swing High State | VOH | 12 | 13.0 | - | V |
| Output Voltage Swing Low State | VOL | 0.08 | 1.4 | - | V |
| Rise Time | tR | 45 | - | 150 | ns |
| Fall Time | tF | 35 | - | 150 | ns |
| Start Threshold (UVLO) | VTH(ST) | 7.8 | 8.4 | 9.0 | V |
| Minimum Operating Voltage (After Turn On) | VOPR(MIN) | 7.0 | 7.6 | 8.2 | V |
| Storage Temperature Range | TSTG | -65 | - | 150 | °C |
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
- NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC-Q100 Qualified and PPAP Capable
Applications
The UC3845BVN is designed for use in Off-Line and DC-DC converter applications. It is particularly suited for power supply designs that require high efficiency, reliability, and minimal external components. These include but are not limited to:
- Switch Mode Power Supplies (SMPS)
- DC-DC Converters
- Power Factor Correction (PFC) Circuits
- Automotive Power Systems
- Industrial Power Supplies
Q & A
- What is the primary function of the UC3845BVN?
The UC3845BVN 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 UC3845BVN?
The oscillator frequency is typically around 52 kHz, with a range of 47 kHz to 57 kHz. - What is the maximum output current of the UC3845BVN?
The maximum output current is 1.0 A. - What are the undervoltage lockout (UVLO) thresholds for the UC3845BVN?
The UVLO thresholds are 7.8 V (on) and 7.0 V (off). - What types of packages are available for the UC3845BVN?
The device is available in 8-pin dual-in-line and surface mount (SOIC-8) packages, as well as a 14-pin plastic surface mount (SOIC-14) package. - Is the UC3845BVN RoHS compliant?
Yes, the UC3845BVN is Pb-Free and RoHS compliant. - What is the storage temperature range for the UC3845BVN?
The storage temperature range is -65°C to +150°C. - How is the oscillator frequency programmed in the UC3845BVN?
The oscillator frequency is programmed by the values selected for the timing components RT and CT. - What protective features does the UC3845BVN include?
The device includes input and reference undervoltage lockouts with hysteresis, cycle-by-cycle current limiting, and a latch for single pulse metering. - Is the UC3845BVN suitable for automotive applications?
Yes, it is suitable for automotive and other applications requiring unique site and control change requirements; it is AEC-Q100 qualified and PPAP capable.
