• • • TEST & MEASUREMENT • • •
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
Figure 2. Power solution for isolated bipolar supply system with low supply ripple.
precision multichannel data acquisition using precision ADCs such as the 18-/20-bit AD4003/AD4020. In CN-0345, an LC tank circuit is used to filter the switching ripple from the ADP5070 instead of using an LDO regulator as shown in Figure 1. In reference design CN-0385, positive and negative LDO regulators (ADP7118 and ADP7182) are used after the ADP5070 to filter the switching ripple. An example for powering a bipolar 20-bit precision DAC like the AD5791 with the ADP5070 can be found in the evaluation board user guide. These examples show how high levels of
precision performance can be maintained while using switching regulators like the ADP5070 to generate bipolar supplies in applications such as data acquisition and precision power supplies/sources.
Isolated bipolar power supplies When a precision test and measurement instrument needs to be isolated for safety reasons, this brings challenges in delivering sufficient power efficiently across the isolation barrier. In multichannel isolated instruments, channel-to- channel isolation means a power solution per channel. This necessitates a compact power solution that can deliver power efficiently. Figure 2 shows a solution for delivering isolated power with bipolar rails. The ADuM3470 and LTM8067 allow us to deliver
power over the isolation barrier up to ~400mA at 5V isolated output with high efficiency. The LTM8067 is a µModule solution integrating the transformer and other components that simplify the design and layout of the isolated power solution while minimising the PCB footprint and bill of materials. The LTM8067 isolates up to 2kVrms. For an even lower output ripple, the LTM8068 incorporates an output LDO regulator that reduces the output ripple from 30mVrms to 20Vrms at the expense of the lower output current of 300mA. The ADuM3470 family uses an external
transformer to deliver isolated power while also integrating digital isolation channels for data transfer and control of ADCs and DACs. Depending on how the isolation solution is configured, the isolated power output can be followed with a power solution similar to Figure 1, as shown in Figure 2 to generate ±15V rails on the isolated side from a single positive supply. Alternatively, the ADuM3470 design can be configured to generate bipolar supplies directly without the need for an extra switcher stage. This results in a smaller PCB area solution at the expense of efficiency. The ADuM3470 isolates up to 2.5kVrms, but the ADuM4470 family can be used for higher levels of voltage isolation up to 5kVrms.
18 ELECTRICAL ENGINEERING • JUNE 2026 CN-0385 is an example of a reference design
that implements the ADuM3470 solution, as seen in Figure 2. The ADP5070 is used on the isolated side to generate the bipolar ±16V rails from an isolated 5.5V. This reference design makes use of the digital isolated channels also included in the 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 - ADC, and CN-0233, which highlights the same isolated power solution of a 16-bit bipolar DAC.
integration make it a great fit for space constrained applications while simplifying and speeding up the design and layout of a switching regulator supply.
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Silent Switcher technology combined with the high levels of integration found in µModule solutions solve the challenge of increasing density needs for precision applications.
If greater customisation is needed at the
Figure 3. Power solution for stepping down to lower voltage rails with low EMI.
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
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. 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.
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