Designing the 5V Rail for Your МК контроллера полёта: TPS563201 Deep Dive

Why the 5V Buck Design Matters

Flight controller power supply design is underappreciated. An unstable 5V rail causes MCU brown-outs during hard maneuvers when battery voltage sags. High-frequency switching noise couples into your SPI IMU lines and corrupts gyro readings. Poor layout creates ground loops that appear as unexplained OSD flickering.

The TPS563201 from Texas Instruments is a 3A synchronous buck converter specifically designed for compact, efficient power supplies in industrial and consumer electronics — making it a natural fit for FPV flight controllers running from 3S–6S LiPo batteries.

TPS563201 Key Specifications

Schematic Walkthrough: Standard 5V FC Application

A minimal TPS563201 5V rail requires just 6 external components:

• L1 (Inductor): 2.2 μH, 4A rated — see sizing below
• C_in: 10 μF / 25V ceramic X5R (2× in parallel for low ESR)
• C_out: 22 μF / 6.3V ceramic X5R (2× in parallel)
• R_top: 560 kΩ (feedback divider upper)
• R_bot: 180 kΩ (feedback divider lower for 5.0V output)
• C_boot: 100 nF (bootstrap capacitor; required)

The output voltage is set by: V_out = 0.8 × (1 + R_top/R_bot). For 5.0V output: R_top/R_bot = (5.0/0.8) – 1 = 5.25. Use 560 kΩ / 107 kΩ (use standard 110 kΩ for 4.96V) or 560 kΩ / 180 kΩ for slightly higher 5.04V.

Inductor Selection for Minimum Noise

The inductor is the single most important component for noise performance. Selection criteria for a 5V / 3A / 570 kHz design:

Critical: Never use an unshielded inductor for this application. The magnetic field from an open drum core at 570 kHz will directly inject noise into nearby magnetometers and gyros. Use a molded-body shielded inductor like the Würth 744043220 or equivalent.

PCB Layout Rules for Minimum Noise

Layout has a larger impact on output noise than component selection. Follow these rules strictly:

• Hot loop minimization: C_in, Q1 (SW high-side), and the inductor form the primary switching loop. Keep this loop area as small as possible — target < 25 mm².
• Ground plane integrity: Use a continuous ground plane under the converter. Never cut the ground plane for routing. The switching return current creates a high-di/dt loop.
• Feedback network placement: Place R_top and R_bot close to the FB pin and route away from the SW node. Any coupling from the switching node to the feedback pin causes output voltage ripple.
• Isolation: If possible, place the converter in a separate zone from the IMU and MCU. Use ferrite beads in the 5V distribution trace if sensitive analog circuitry is present.
• Thermal via: Place 4–6 thermal vias under the SOT-23 exposed pad to the ground plane for heat spreading.

Alternative Buck ICs for FC Design

Several other buck converters are commonly used in FC designs, each with trade-offs:

Measured Output Noise Results

Using a Rigol DS1054Z with 100 MHz bandwidth and proper probe technique (ground lead minimized), a well-laid-out TPS563201 design typically achieves:

• Output ripple (peak-to-peak): 12–18 mV at 570 kHz switching frequency
• Transient response (0 to 2A step): < 80 mV overshoot, settling within 20 μs
• IMU gyro noise (measured via Betaflight blackbox): Equivalent to or better than linear regulator designs

Часто задаваемые вопросы

Связанные статьи & Products