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Figure 3. Power solution for stepping down to lower voltage rails with low EMI.
ADuM3470. A similar design that uses the ADuM3470 is CN-0393. This is a bank isolated data acquisition system based on the ADAQ7980/ADAQ7988 µModule ADC. In this design, the ADuM3470 is configured with an external transformer and Schottky diode full wave rectifier to generate ±16.5V directly without the need for an additional regulator stage. This allows for a smaller footprint solution at the expense of lower efficiency. A similar solution is shown in CN-0292, which is a 4-channel data acquisition solution based
on the AD7176 ∑-Δ ADC, and CN-0233, which highlights the same isolated power solution of a 16-bit bipolar DAC.
These examples show how to deliver isolated power for precision levels of performance in isolated data acquisition or isolated power supplies while maintaining a small PCB footprint or high levels of power efficiency.
SILENT SWITCHER ARCHITECTURE TO EFFICIENTLY STEP DOWN WITH LOW NOISE
In the power supply scheme shown in Figure 1, an LDO regulator is used to step down from 15V to 5V/3.3V. This is not a very efficient way of generating these low voltage rails. A solution to improve the efficiency of stepping down to lower voltages using the Silent Switcher, µModule regulator LTM8074 is shown in Figure 3. The LTM8074 is a Silent Switcher, µModule
step-down regulator in a small, 4mm × 4mm footprint BGA package capable of delivering up to 1.2A with low radiated noise. Silent Switcher technology cancels stray fields generated by the switching currents, thereby reducing conducted and radiated noise. The high efficiency of this µModule device with its very low radiated noise
makes it a great choice for powering noise sensitive precision signal chains. Depending on the PSRR of the components connected to the output supply such as amplifiers, DACs, or ADCs, it may be possible to power them directly from the Silent Switcher output without the need for an LDO regulator to further filter the supply ripple as is needed for traditional switchers. Its high output current of 1.2A also means it could be used to power the digital hardware in a system such as an FPGA if needed. The LTM8074’s small footprint and high level of integration make it a great fit for space constrained applications while simplifying and speeding up the design and layout of a switching regulator supply.
If greater customisation is needed at the expense of PCB area, then a discrete implementation of a Silent Switcher device can be achieved by using a product like the LT8609S. These products include a spread spectrum mode to spread the ripple energy at the switching frequency over a frequency band.
This reduces the amplitude of spurious tones showing up in a precision system from the supplies. Silent Switcher technology combined with the high levels of integration found in µModule solutions solve the challenge of increasing density needs for precision applications, such as multichannel source measure units, without compromising the high resolution levels of performance that system designers need to achieve.
CONCLUSION
Generating bipolar power supply systems with isolation for precision electronic test and measurement can be a balancing act between system performance, maintaining a small footprint, and power efficiency. Here we have shown solutions and products that help meet these challenges and allow the system designer to make the right trade-offs.
Analog Devices
www.analog.com
ANALOG DEVICES SPONSORS FORMULA STUDENT TEAM WOB-RACING FOR 2023 SEASON
nalog Devices is supporting the first roll-out of Team wob-racing’s latest Formula Student race car, the WR17. As a platinum sponsor of the student team, ADI continues to support the future of engineering talent in the automo- tive industry. The race car utilises a wide range of ADI’s technology within the electric vehicle powertrain, including within the in- verter assembly and battery management system. With ADI’s broad portfolio of cutting- edge technology, it was a natural progres- sion for Team wob-racing to approach ADI for sponsorship of the team for their 2023 season, alongside other automotive ecosys- tem players such as Vector and Bertrandt. Founded 20 years ago by students of the
A 50 June 2023 Instrumentation Monthly
Faculty of Automotive Engineering at the Ostfalia University of Applied Sciences, Team wob-racing is one of the oldest For- mula Student racing teams in Germany. In 2011, the project pivoted to designing elec- tric vehicles. The latest concept, the WR17, is the team’s most optimised design thus far. It is capable of accelerating to 100km/h within 2.2 seconds. Effective energy man- agement is a critical capability for electric
vehicles to achieve better performance and longer range, and ADI continues to lead that charge through its innovations in auto- motive electrification technology. The future engineers made one of the biggest innovations in the team's history with their new in-house developed inverters. Alongside the battery management system, the inverters are another important compo- nent of the race car, which uses many ADI parts. To complete the development, the team was able to use an axle test rig from their sponsor Bertrandt to evaluate the best possible electronic control of the system.
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