Low noise buck converter integrates ferrite bead compensation

October 23, 2020 //By Nick Flaherty
Low noise buck converter integrates ferrite bead compensation
Integrated ferrite-bead compensation in TI's TPS6291x DC-DC regulator provides higher precision for noise-sensitive applications

Texas Instruments has launched a family of low-noise DC-DC switching regulators with integrated ferrite-bead compensation.

The 17V TPS62912 and TPS62913 offer low noise of 20 µVRMS for frequencies ranging from 100 Hz to 100 kHz and ultra-low output-voltage ripple of 10 µVRMS, giving engineers the ability to remove one or more low-dropout regulators (LDOs) from their designs, reduce power losses by up to 76 percent with a third the board area.

Noise in the power supply is a key design challenge in many high-precision test and measurement, medical, aerospace and defence, and wireless infrastructure applications. A traditional low-noise power-supply architecture includes a DC-DC converter with a low-noise LDO such as the TPS7A52, TPS7A53 or TPS7A54 and an off-chip filter such as a ferrite bead. By integrating ferrite-bead compensation, the 2A TPS62912 and 3A TPS62913 use the ferrite bead already present in most systems as an effective filter against high-frequency noise, reducing the power supply output voltage ripple by approximately 30 dB and simplifying the power supply design.

High-precision systems require supply rails with low noise and low ripple to preserve signal accuracy and integrity. The TPS62912 and TPS62913 offer both, along with a power-supply rejection ratio of 65 dB at up to 100 kHz. In addition, this buck converter family has an output-voltage error of less than 1%, which helps ensure tight output-voltage accuracy. Both converters enable the use of spread-spectrum frequency modulation to further attenuate radio-frequency spurs and allow synchronization to an external clock so engineers can easily meet their signal-to-noise ratio (SNR) and spurious-free dynamic range (SFDR) targets, which are critical in applications such as medical imaging or radar.

Designers have to address the trade-off between noise and efficiency when powering sensitive analogue circuis. Using a switching regulator on its own would result in too much switching noise, while adding a post-regulator LDO to reduce noise would lead to additional power losses, especially at high load currents.

The peak efficiency of 97 percent for the TPS62912 and TPS62913

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