AU8120
High-current synchronous buck converter with 4.5V to 36V input and integrated MOSFETs for industrial applications.
Product Overview
Description
The AU8120 is a high-current synchronous buck converter designed for industrial and automotive applications. It delivers up to 5A continuous output current with integrated high-side and low-side MOSFETs.
With a wide input voltage range from 4.5V to 36V, the AU8120 supports 12V, 24V, and industrial bus voltages. Peak efficiency of 96% minimizes heat generation and simplifies thermal design.
The device features programmable soft-start, power-good indicator, and comprehensive protection including over-current, over-temperature, and under-voltage lockout.
Product Series
AU
Primary Application
Industrial control systems
Key Features
- Wide 4.5V to 36V input range
- 5A continuous output current
- Integrated MOSFETs
- 96% peak efficiency
- Programmable soft-start
- Power-good indicator
Specifications
| Input Voltage | 4.5V to 36V |
|---|---|
| Output Voltage | 0.8V to 0.9×VIN |
| Output Current | 5A continuous |
| Efficiency | Up to 96% |
| Switching Frequency | 300kHz to 2MHz |
| Package | QFN-24 |
Applications
Industrial control systems
Industrial automation and control
Automotive electronics
Automotive and EV electronics
Telecom equipment
Electronic system design
Distributed power systems
Electronic system design
Battery chargers
Battery and charging management
FAE Expert Insights
"The AU8120 is a great mid-range buck converter. The 5A capability handles most industrial loads, and the 36V input supports 24V systems with margin. Efficiency is excellent - I've measured 95%+ in real applications. The integrated MOSFETs save significant board space compared to controllers with external FETs. Thermal performance is good with proper copper area. I typically run at 500kHz for good efficiency with reasonable inductor size. The power-good indicator is handy for sequencing. A solid choice for industrial power applications."
5A buck converter with wide input range and integrated MOSFETs
— David Liu, BeiLuo
Frequently Asked Questions
What inductor should I use?
For the AU8120, select an inductor with: (1) Saturation current >6A (20% margin above 5A); (2) DCR <10mΩ for good efficiency; (3) Inductance 4.7-10μH at 500kHz. Recommended part numbers are in the datasheet. Use shielded inductors for EMI-sensitive applications.
Use 6.8μH shielded inductor with >6A saturation current.
How much copper area is needed for thermal?
Thermal performance depends on copper area: (1) Minimum - 100mm² for light loads (<3A); (2) Typical - 500mm² for full load at 25°C ambient; (3) High temp - 1000mm² or more for 85°C ambient. Use multiple vias to inner ground planes. The datasheet provides thermal curves for different copper configurations.
Use 500mm² copper for typical applications; 1000mm² for high ambient temps.
What is the switching frequency range?
The AU8120 supports 300kHz to 1MHz switching frequency, set by an external resistor. Higher frequencies allow smaller inductors and capacitors but reduce efficiency. Lower frequencies improve efficiency but require larger components. I typically use 500kHz as a good balance. The frequency can be adjusted during design but is fixed during operation - it does not dynamically change with load.
Use 500kHz for good balance; higher for compact designs, lower for maximum efficiency.
Can AU8120 be synchronized to an external clock?
Yes, the AU8120 supports external synchronization through the SYNC pin. Apply a clock signal (400kHz to 1.2MHz) to synchronize multiple converters or avoid beating frequencies in multi-rail systems. When synchronized, the device locks to the external frequency. If the external clock is lost, the device automatically switches to the internal oscillator set by the frequency resistor. This feature is useful for EMI-sensitive applications where specific frequencies must be avoided.
Use SYNC pin for multi-converter synchronization or EMI frequency planning.
What is the soft-start time and how is it programmed?
The AU8120 features programmable soft-start to limit inrush current during startup: (1) Soft-start time is set by an external capacitor connected to the SS pin; (2) Typical range: 1ms to 10ms with capacitor values of 10nF to 100nF; (3) Formula: tSS = CSS × 0.8V / 10μA; (4) For 5ms soft-start, use 47nF capacitor; (5) Soft-start prevents output voltage overshoot and reduces input current surge. The soft-start capacitor should be placed close to the SS pin. This feature is essential for applications with large output capacitors or current-limited input sources.
Use 47nF for 5ms soft-start; adjust based on output capacitance.