Overview
The LM5021MMX-2/NOPB is an off-line pulse width modulation (PWM) controller produced by Texas Instruments. This device is designed to implement highly efficient off-line single-ended flyback and forward power converters using current-mode control. It features an ultra-low start-up current of 25 µA, which minimizes power losses in the high voltage start-up network. The LM5021 also includes a skip cycle mode to reduce power consumption with light loads, making it suitable for energy-conserving applications such as those compliant with ENERGY STAR® and CECP standards.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Package | VSSOP-8, PDIP-8 | |
| Operating Temperature Range | -40 to 125 | °C |
| Maximum Duty Cycle | 50% (LM5021-2) | |
| Oscillator Frequency | Up to 1 MHz (programmable) | |
| Peak Gate Driver Current | 0.7 A (sink), 0.3 A (source) | A |
| Current Sense Threshold | 500 mV | mV |
| Storage Temperature Range | -65 to 150 | °C |
| Switching Frequency | Programmable using RT pin resistor |
Key Features
- Ultra-low start-up current (25 µA maximum)
- Current mode control
- Skip cycle mode for low standby power
- Single resistor programmable oscillator
- Synchronizable oscillator
- Adjustable soft-start
- Integrated 0.7 A peak gate driver
- Direct opto-coupler interface
- Under-voltage lockout (UVLO) with hysteresis
- Cycle-by-cycle over-current protection
- Hiccup mode for continuous overload protection
- Leading edge blanking of current sense signal
Applications
- DCM/CCM Flyback Converters
- Industrial Power Conversion
- SMPS for Smart Meters and Audio Amplifiers
- Building Automation and White Goods SMPS
- Isolated Telecom Power Supplies
Q & A
- What is the primary function of the LM5021MMX-2/NOPB?
The LM5021MMX-2/NOPB is an off-line pulse width modulation (PWM) controller designed for implementing highly efficient off-line single-ended flyback and forward power converters using current-mode control.
- What is the start-up current of the LM5021MMX-2/NOPB?
The start-up current is ultra-low, with a maximum of 25 µA.
- What is the maximum duty cycle for the LM5021-2 version?
The maximum duty cycle for the LM5021-2 version is 50%.
- How is the oscillator frequency programmed in the LM5021MMX-2/NOPB?
The oscillator frequency is programmed using a single external resistor connected between the RT pin and GND.
- What protection features does the LM5021MMX-2/NOPB include?
The device includes under-voltage lockout (UVLO) with hysteresis, cycle-by-cycle over-current protection, and hiccup mode for continuous overload protection.
- What is the purpose of the skip cycle mode in the LM5021MMX-2/NOPB?
The skip cycle mode reduces power consumption with light loads, making it suitable for energy-conserving applications.
- What is the peak gate driver current capability of the LM5021MMX-2/NOPB?
The peak gate driver current is 0.7 A (sink) and 0.3 A (source).
- What is the current sense threshold for over-current protection?
The current sense threshold is 500 mV.
- What are some typical applications of the LM5021MMX-2/NOPB?
Typical applications include DCM/CCM Flyback Converters, Industrial Power Conversion, SMPS for Smart Meters and Audio Amplifiers, Building Automation and White Goods SMPS, and Isolated Telecom Power Supplies.
- What is the operating temperature range of the LM5021MMX-2/NOPB?
The operating temperature range is -40°C to 125°C.
