Low noise buck converter integrates ferrite bead compensation
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 allows engineers to design for noise filtering without an LDO, reducing power losses by up to 76 percent – 1.8 W in analogue front-end (AFE) designs and 1.5 W in designs using a wideband analogue-to-digital converter (ADC), such as the ADC12DJ5200RF.
This also eliminates the LDO and associated passive components, which can save approximately 20 mm2 of printed circuit board (PCB) area per LDO. Designs that typically use a single LDO can save 36 percent of PCB space as a result. The integrated ferrite-bead compensation of the buck converters helps to reduce the overall DC-DC component count by eliminating two capacitors and two resistors.
Pre-production quantities of the 2A TPS62912 and 3A TPS62913 are available now, only on TI.com, in a 2 x 2mm 10-pin quad flat no-lead (QFN) package. Pricing starts at US$1.06 and US$1.16 respectively, in 1,000-unit quantities. TI expects both devices to be available in volume production in the first quarter of 2021.
The TPS62912EVM and TPS62913EVM evaluation modules are available on TI.com for US$49.
TI will demonstrate the TPS62913 in its virtual booth at the electronica virtual conference from November 9-12, 2020 a www.ti.com/about-ti/trade-shows/electronica.html
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