Product information# Technical Documentation: FAN5026MTC Dual Synchronous Buck Controller
Manufacturer : FAIRCHILD (ON Semiconductor)
Component : FAN5026MTC
Description : Dual-Output, Synchronous Buck PWM Controller with Integrated Drivers
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## 1. Application Scenarios
### Typical Use Cases
The FAN5026MTC is a high-performance, dual-output PWM controller designed to regulate two independent voltage rails in sophisticated digital systems. Its primary use cases include:
* Dual-Voltage Power Supply Generation : Simultaneously providing core voltage (Vcore) and I/O voltage (Vio) or auxiliary voltages (e.g., 3.3V and 1.8V) from a single, higher input bus (typically 5V or 12V).
* Point-of-Load (POL) Regulation : Serving as the central controller for distributed power architectures in large systems, delivering clean, tightly regulated power directly to high-current loads like ASICs, FPGAs, or processor clusters.
* Sequenced Power-Up/Rail Management : Its independent enable pins and power-good outputs facilitate controlled power sequencing, which is critical for complex digital ICs to prevent latch-up and ensure reliable startup.
### Industry Applications
This component is predominantly found in applications requiring compact, efficient, and reliable multi-rail power conversion:
* Computing & Servers : Motherboards, graphics cards, blade servers, and storage systems for powering CPUs/GPUs, memory, and chipset rails.
* Networking & Telecommunications : Routers, switches, baseband units, and line cards where multiple low-voltage, high-current rails are needed for processors and high-speed transceivers.
* Industrial Electronics : Test and measurement equipment, automation controllers, and embedded computing modules.
### Practical Advantages and Limitations
Advantages:
* High Efficiency (>90% typical) : Utilizes synchronous rectification (integrated low-side MOSFET drivers) to minimize conduction losses, especially critical at lower output voltages.
* Compact Solution : Integrating two controllers and drivers into a single 28-pin TSSOP package saves significant board area compared to discrete solutions.
* Excellent Regulation & Transient Response : Voltage-mode control with input voltage feed-forward provides fast response to line and load changes.
* Design Flexibility : Adjustable switching frequency (100kHz to 1MHz+), soft-start, and independent enable controls allow optimization for specific applications.
* Comprehensive Protection : Features include over-current protection (OCP), over-voltage protection (OVP), and under-voltage lockout (UVLO).
Limitations:
* External Power Stage Required : Requires the selection and layout of external MOSFETs, inductors, and capacitors, which increases design complexity and BOM count.
* Controller-Only Solution : Lacks integrated MOSFETs, limiting its use in very low-current or space-constrained applications where a fully integrated regulator might be preferable.
* Sensitive Layout : As a high-frequency switching controller, performance is highly dependent on proper PCB layout to minimize noise and ringing.
* Thermal Management : The external MOSFETs and inductor are the primary heat sources; their thermal design is crucial and falls on the system designer.
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## 2. Design Considerations
### Common Design Pitfalls and Solutions
1. Pitfall: Instability or Poor Transient Response.
* Cause : Incorrect compensation network design for the output LC filter.
* Solution : Carefully calculate Type-II or Type-III compensation components based on the chosen output inductor, capacitor ESR, and desired crossover frequency. Use the manufacturer's design tools or application notes.
2. Pitfall: Excessive Switching Node Ringing or EMI.
* Cause : High parasitic inductance in the high-current loop (Input Cap →
