How to address DC/DC noise, efficiency, and layout issues using integrated power modules
These Silent Switcher µModules represent the evolution of step- down regulator design and packaging from an IC with support components to an LQFN IC with integral capacitors to a µModule with requisite capacitors and inductors ( Figure 8 ). Broad offering addresses needs, tradeoffs The Silent Switcher µModules comprise many individual units with different ratings for input voltage range, output voltage rail, and output current. For example, the LTM8003 is a 3.4 to 40-volt input, 3.3-volt output, 3.5 A continuous (6 A peak) µModule that meets CISPR 25 Class 5 limits, yet measures just 9 × 6.25 millimeters (mm) and 3.32 mm high ( Figure 9 ). It is offered in a pinout which is failure mode effects analysis (FMEA) compliant (LTM8003-3.3), meaning that the output stays at
Figure 7: An internal layout with current loops in opposite directions also cancels undesired magnetic fields. (Image source: Analog Devices)
or below the regulation voltage during an adjacent-pin short circuit or if a pin is left floating. The typical quiescent current is just 25 microamperes (µA), and the H-grade version is rated for 150°C operation. The DC2416A demonstration (demo) board is available for designers to exercise the regulator and assess its performance for their application ( Figure 10 ). Two nominally similar Silent Switcher µModule family members, the LTM4657 (3.1 to 20-volt input; 0.5 to 5.5 volt @8 A output) and the LTM4626 (3.1 to 20-volt input; 0.6 to 5.5 volt at 12 A output), show the nature of the tradeoffs that the
devices offer. The LTM4657 uses a higher value inductor than the LTM4626, allowing it to operate at lower frequencies to decrease switching loss.
The LTM4657 is a better solution for high switching losses and low conduction losses, such as in applications where the load
Figure 8: By incorporating capacitors and an inductor in the package, the Silent Switcher µModules are the third stage in the advancement of IC- centric switching regulators. (Image source: Analog Devices)
Figure 9: The LTM8003 Silent Switcher is a tiny, self-contained package that easily meets the CISPR 25 Class 5 Peak Radiated energy limit from DC to 1000 MHz. (Image source: Analog Devices)
Figure 10: The DC2416A demo board simplifies connection with and evaluation of the LTM8003 Silent Switcher device. (Image source: Analog Devices)
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