Overview
The LM5021MMX-1/NOPB is an AC-DC current-mode PWM controller produced by Texas Instruments. This controller is designed for use in off-line single-ended flyback and forward power converters, as well as boost converters. It features an ultra-low startup current of 25 µA, minimizing power losses in the high voltage start-up network. The LM5021 includes a range of features to enhance efficiency and reliability, such as skip cycle mode for low standby power, adjustable soft-start, and hiccup mode for continuous overload protection.
Key Specifications
| Parameter | Minimum | Typical | Maximum | Unit |
|---|---|---|---|---|
| VIN Voltage | 8 | - | 30 | V |
| Operating Junction Temperature | -40 | - | 125 | °C |
| Maximum Duty Cycle (LM5021-1) | - | - | 80% | % |
| Maximum Duty Cycle (LM5021-2) | - | - | 50% | % |
| Peak Gate Driver Current (Source) | - | - | 0.3 A | A |
| Peak Gate Driver Current (Sink) | - | - | 0.7 A | A |
| Oscillator Frequency | - | - | Up to 1 MHz | Hz |
| Package Type | - | - | VSSOP-8 or PDIP-8 | - |
Key Features
- Ultra-low startup current of 25 µA
- Current mode control with skip cycle mode for low standby power
- Single resistor programmable oscillator with synchronization capability
- Adjustable soft-start to minimize startup stresses
- Hiccup mode for continuous overload protection
- Under-voltage lockout (UVLO) with hysteresis
- Cycle-by-cycle overcurrent protection with leading edge blanking of current sense signal
- Integrated 0.7-A peak gate driver
- Direct opto-coupler interface
- Slope compensation for LM5021-1 to prevent sub-harmonic oscillations
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 maximum duty cycle for the LM5021-1 and LM5021-2?
The LM5021-1 has a maximum duty cycle of 80%, while the LM5021-2 has a maximum duty cycle of 50%.
- What is the startup current of the LM5021?
The startup current of the LM5021 is 25 µA maximum.
- How is the oscillator frequency programmed in the LM5021?
The oscillator frequency is programmed using a single external resistor connected between the RT pin and GND.
- What protection features does the LM5021 offer?
The LM5021 offers cycle-by-cycle overcurrent protection, hiccup mode for continuous overload protection, and under-voltage lockout (UVLO) with hysteresis).
- What is the purpose of the soft-start feature in the LM5021?
The soft-start feature allows the power converter to gradually reach the initial steady state operating point, reducing startup stresses and current surges).
- Can the LM5021 be synchronized to an external clock source?
- What are the package options for the LM5021?
The LM5021 is available in VSSOP-8 and PDIP-8 packages).
- What is the peak gate driver current capability of the LM5021?
The LM5021 can source a peak current of 0.3 A and sink a peak current of 0.7 A).
- Is the LM5021 RoHS compliant?
- What is the typical operating junction temperature range for the LM5021?
The typical operating junction temperature range for the LM5021 is -40°C to 125°C).
