Overview
The UC3845D8G4 is a current-mode PWM controller from Texas Instruments, part of the UCx84x family. This integrated circuit is designed to implement off-line and DC-to-DC fixed-frequency current-mode control schemes with a minimal number of external components. It features a low start-up current of less than 1 mA, automatic feedforward compensation, pulse-by-pulse current limiting, and enhanced load-response characteristics. The device includes an undervoltage lockout (UVLO) with hysteresis, double-pulse suppression, and a high-current totem-pole output stage suitable for driving N-channel MOSFETs.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| VCC (Low impedance source) | - | - | 30 | V |
| IVCC (Self Limiting) | - | - | 30 mA | mA |
| VFB and VISENSE (Analog input voltage) | -0.3 | - | 6.3 | V |
| IOUTPUT (Output drive current) | - | - | ±1 A | A |
| ICOMP (Error amplifier output sink current) | - | - | 10 mA | mA |
| EOUTPUT (Output energy, capacitive load) | - | - | 5 µJ | µJ |
| TJ (Junction temperature) | - | - | 150 °C | °C |
| Tstg (Storage temperature) | -65 | - | 150 °C | °C |
| TA (Operating free-air temperature) | 0 | - | 70 °C | °C |
| VVREF (Reference voltage) | 4.9 | 5 | 5.1 | V |
| fOSC (Oscillator frequency) | 100 | - | 500 kHz | kHz |
| VCCON (UVLO enable threshold) | 14.5 | 16 | 17.5 | V |
| VCCOFF (UVLO off threshold) | 8.5 | 10 | 11.5 | V |
| DMAX (Maximum duty cycle) | 47% | 48% | 50% | % |
Key Features
- Optimized for off-line and DC-to-DC converters
- Low start-up current (< 1 mA)
- Automatic feedforward compensation
- Pulse-by-pulse current limiting
- Enhanced load-response characteristics
- Undervoltage lockout with hysteresis
- Double-pulse suppression
- High-current totem-pole output stage
- Internally trimmed bandgap reference
- Up to 500-kHz operation
- Error amplifier with low output resistance
Applications
- Switching regulators of any polarity
- Transformer-coupled DC-DC converters
Q & A
- What is the UC3845D8G4 used for?
The UC3845D8G4 is used to implement off-line and DC-to-DC fixed-frequency current-mode control schemes in power supply applications.
- What is the operating temperature range of the UC3845D8G4?
The operating temperature range of the UC3845D8G4 is from 0°C to 70°C.
- What is the maximum duty cycle of the UC3845D8G4?
The maximum duty cycle of the UC3845D8G4 is up to 50%.
- What is the start-up current of the UC3845D8G4?
The start-up current of the UC3845D8G4 is less than 1 mA.
- What type of output stage does the UC3845D8G4 have?
The UC3845D8G4 has a high-current totem-pole output stage suitable for driving N-channel MOSFETs.
- What is the purpose of the undervoltage lockout (UVLO) in the UC3845D8G4?
The UVLO in the UC3845D8G4 ensures that the device operates only when the input voltage is within a safe range, preventing damage from low voltage conditions.
- What is the oscillator frequency range of the UC3845D8G4?
The oscillator frequency range of the UC3845D8G4 is from 100 kHz to 500 kHz.
- What type of compensation does the UC3845D8G4 offer?
The UC3845D8G4 offers automatic feedforward compensation and allows for external compensation components to be connected to the error amplifier compensation pin.
- What is the reference voltage of the UC3845D8G4?
The reference voltage of the UC3845D8G4 is 5 V with a tolerance of ±0.1 V.
- What are the typical applications of the UC3845D8G4?
The UC3845D8G4 is typically used in switching regulators of any polarity and transformer-coupled DC-DC converters.
