TEST & MEASUREMENT ANALOG DEVICES
As well as simplifying the design challenge in terms of selecting components and board layout for switching regulators, the LTM8049 also minimises the PCB footprint and bill of materials needed for generating bipolar supplies. choice. Although the ADP5070 solution requires more external components, like inductors and diodes, it allows for more customisation of the power solution. Both the ADP5070 and LTM8049 have sync pins that can be used to synchronise the switching frequency with the clock of an ADC to avoid switching the internal FETs during sensitive time periods for an ADC. The high instrument supplies. The LT3032 incorporates both a positive and negative low noise LDO regulator in a single package with wide operating range. The LT3023 incorporates two low noise, positive LDO regulators with a wide operating range. rejection from the switching regulator stage. Both LDO regulators are available in small LFCSP packages that reduce the PCB footprint and simplify the bill of materials. If much higher levels
Figure 2: Power solution for isolated bipolar supply system with low supply ripple
of PSRR are required from the LDO regulator to further reduce the switching ripple in the MHz range, then LDO regulators like the LT3094/ LT3045 should be considered. The choice of how much PSRR is required in the LDO stage will depend on the PSRR of the components, like from the supply rails. Generally, higher PSRR quiescent current.
CN-0345 and CN-0385 are two examples of
reference designs that implement this solution by using the ADP5070. These designs are for precision multichannel data acquisition using AD4020.
the switching ripple from the ADP5070 instead of reference design CN-0385, positive and negative
ISOLATED BIPOLAR POWER SUPPLIES When a precision test and measurement instrument needs to be isolated for safety reasons, this brings challenges in delivering barrier. In multichannel isolated instruments, channel-to-channel isolation means a power solution per channel. This necessitates a compact Figure 2 shows a solution for delivering isolated power with bipolar rails.
ripple. An example for powering a bipolar 20- 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.
22 November 2024 Irish Manufacturing
www.irish-manufacturing.com
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