SSZT346 January   2020 LMR36503 , LMR36506 , TPS7A47 , TPSM265R1


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    2.     High Input Voltage, Higher Stakes
    3.     Big Challenge, Small Solution
    4.     Lowering EMI, Raising the Standard
    5.     Conclusion
    6.     Additional Resources:

Arief Hernadi

As the factory automation and control equipment market evolves, shipments of equipment with sensors such as field transmitters, machine vision and position sensors are increasing. As a result, the demand for feature-rich power integrated circuits (ICs) that could power these devices is also growing.

Figure 1 shows a block diagram of a temperature transmitter. The nonisolated power-supply subsystem (highlighted in red) consists of a low dropout regulator (LDO), a DC/DC converter or a power module. In an earlier technical article, “Powering tiny industrial automation control equipment with high-voltage modules: how to ensure reliability,” my colleague Akshay Mehta explained how to power miniature industrial automation control equipment with high-voltage modules. In this article, I’ll take a look at how to use buck converters and LDOs for the same purpose.

GUID-22411541-379D-44C3-8080-A14EDD85C1FF-low.jpg Figure 1 Temperature Transmitter Subsystem

High Input Voltage, Higher Stakes

There are a number of ways to regulate the input DC voltage in factory automation and control equipment. You can use an LDO, a DC/DC converter or a power module. LDOs such as the TPS7A47 are commonly used in sensor power supplies due to their simple design and ability to attenuate input noise and deliver a ripple-free output voltage. DC/DC converters are a good choice for applications operating at lower output voltages, higher input voltages or higher output currents. For example, the LMR36503 and LMR36506 DC/DC converters enable a low shutdown current specification of 1 µA and an operating quiescent current specification of 7 µA. For loads with low output currents – less than 20 mA – these performance specifications ensure higher efficiency for 4- to 20-mA loop applications. Figure 2 shows the efficiency and thermal performance of the LMR36506 converter.

GUID-D8D83EAE-16CD-416B-B51A-E95F594CF97A-low.jpg GUID-E749F8D8-7100-4601-9458-49381015B979-low.jpg Figure 2 Efficiency and Thermal Performance at 24 vIN, 5 VOUT, 2.1 Mhz at 0.6A

Big Challenge, Small Solution

TPSM265R1 LMR36503 LMR36506 IN OUT
GUID-43164A53-60DC-4B0D-B09F-A842CB24EFFB-low.jpg Figure 3 LMR36506 Example Solution Size

Lowering EMI, Raising the Standard

GUID-878723F3-B0D1-44FC-B51C-6CAFD8FF43ED-low.jpg Figure 4 An EMI Filter Structure for DC/DC Converters
LMR36503 LMR36506
GUID-8A98C3FF-22B5-4273-90ED-012A3AF9502D-low.jpg Figure 5 Wire-bond Quad Flat No-lead and FCOL Packages



Additional Resources: