Overview
The UC3842DTR 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 | - | - | 30 | V |
| IVCC | - | - | 30 mA | - |
| VVFB and VISENSE | -0.3 | - | 6.3 | V |
| IOUTPUT | - | - | ±1 A | - |
| ICOMP | - | - | 10 mA | - |
| EOUTPUT | - | - | 5 µJ | - |
| TJ | - | - | 150 °C | - |
| Tstg | -65 | - | 150 °C | - |
| fOSC | 100 kHz | - | 500 kHz | - |
| TA (UC384x) | 0 °C | - | 70 °C | - |
| VREF | 4.9 V | 5 V | 5.1 V | - |
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
- Off-line power supplies
- DC-DC applications
Q & A
- What is the UC3842DTR used for?
The UC3842DTR is used to implement off-line and DC-to-DC fixed-frequency current-mode control schemes in power supply applications.
- What is the start-up current of the UC3842DTR?
The start-up current of the UC3842DTR is less than 1 mA.
- What is the operating temperature range for the UC3842DTR?
The operating temperature range for the UC3842DTR is from 0°C to 70°C.
- What is the maximum duty cycle for the UC3842DTR?
The maximum duty cycle for the UC3842DTR can be up to 100% depending on the specific device variant.
- What type of output stage does the UC3842DTR have?
The UC3842DTR 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 UC3842DTR?
The UVLO in the UC3842DTR ensures that the device operates only when the input voltage is within a safe range, preventing damage from low voltage conditions.
- How is the switching frequency set in the UC3842DTR?
The switching frequency in the UC3842DTR is set using an external timing resistor (RRT) and timing capacitor (CCT) connected to the RT/CT pin.
- What is the reference voltage provided by the UC3842DTR?
The UC3842DTR provides a 5-V reference voltage (VREF) which is used for various internal functions and can be bypassed to ground with a ceramic capacitor.
- What are some common applications of the UC3842DTR?
Common applications include switching regulators, transformer-coupled DC-DC converters, off-line power supplies, and DC-DC converters.
- What are the package options available for the UC3842DTR?
The UC3842DTR is available in various package options including SOIC, PDIP, and CFP.
