TPS54331 DCDC ripple interferes with radio

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TPS54331 DCDC ripple interferes with radio [Copy link]

The TPS54331 device is a 28-V, 3-A nonsynchronous step-down converter with an integrated low RDS(on) high-side MOSFET. To improve efficiency at light loads, the pulse-skipping Eco-mode function is automatically activated. In addition, the 1-μA shutdown supply current allows the device to be used in battery-powered applications. Current-mode control with internal slope compensation simplifies external compensation calculations and reduces component count while allowing the use of ceramic output capacitors. A resistor divider programs the hysteresis of the input undervoltage lockout. An overvoltage transient protection circuit limits voltage overshoot during startup and transient conditions. A cycle-by-cycle current limiting scheme, frequency foldback, and thermal shutdown protect the device and load when an overload condition occurs. 3.5V to 28V input, 3A, 570kHz buck converter with Eco-mode I used a TPS54331 to convert 12V to 5V, and then converted it to 3.3V through an LDO to the radio IC. As a result, the interference was very large. Before this, LM2596 was used, which had little interference to the radio. The output ripple was large, but the reason could not be found. Finally, after investigation and comparison with the datasheet of 54331, it was found that 54331 had very high requirements for the input pin. A large non-polar capacitor and several small capacitors must be placed within a few millimeters of the input pin to solve the interference problem. It took 2 days to investigate the problem.