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400mA PWM / VFM Synchronous Buck DC/DC Converter Module with Integrated Inductor

October 26, 2021

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The RM590 Buck DC/DC Converter Module is a remarkable product in a tiny package with a powerful 400mA Buck DC/DC converter and built-in inductor. It provides convenience for the designer but also guarantees high efficiency through synchronous rectification. The high operating frequency of 6 MHz requires a significant small PCB board space thanks to small sized and a low number of external components. The automatic PWM / VFM switching ensures a stable efficiency output over a wide output current range.

Unlike designing circuits with voltage regulators, a circuit with a DC/DC converter is a more complicated task. The designer faces several important decisions that can affect the end result. However, using a DC/DC converter module with built-in inductor makes designing so much easier, while optimizing performance through a PCB design with a small footprint and short leads as well as the synchronous rectification with built-in High and Low side MOSFETS.
The selection of a suitable inductor is a time-consuming job, it also needs to remain available for production lifetime of theapplication as well. The RM590 solves this issue, moreover the embedded inductor also results in a lower EMI emission and can be further reduced by following good design and layout practices.

EMI evaluation result. (VIN=3.6V, Vout=1.1V)

  • External Inductor Type

    External Inductor Type
  • RM590

    RM590
  • We were able to make this small module thanks its high operating frequency of 6 MHz, resulting in lower values of the reactive components. Only an additional input and output capacitor is required on the board, saving valuable PCB board space.

  • RM590Lxx1A/B : Fixed Output Voltage Type

    RM590Lxx1A/B : Fixed Output Voltage Type

Performance characteristics of the RM590 prove that it is a very stable DC/DC converter with a peak efficiency of up to 93%.

  • RM590 Output Current Iout [mA]

    Output Current Iout [mA]

  • RM590 Output Current Iout [mA]

    Output Current Iout [mA]

Two different operating modes are available, controlled by the mode pin:

  1. Automatic PWM/VFM mode: To maintain high efficiency under light and heavy load conditions, the device automatically switches between PWM and VFM mode.
  2. Forced PWM mode: Reduces noise since the frequency is fixed during all load conditions.

Several protection circuits are integrated: An Under Voltage Lock-Out circuit disables the DC/DC Converter in case the input voltage falls below a minimum threshold. A soft-start circuit regulates the output voltage to ramp-up smoothly, preventing any output overshoot and undershoot during the start-up period. The Lx current limit circuit prevents the peak current through the inductor to exceed a specific maximum current threshold. Thermal protection protects the module from overheating when the junction temperature exceeds 140°C.

Targeted applications for the RM590 are products with a high degree of miniaturization such as wearables and portable gadgets as well as other consumer, industrial and IoT devices.
Optional features are selected by the product version, it has an auto-discharge function which rapidly discharges the output capacitor once the CE pin turns off the chip and one can select between a fixed or adjustable output voltage version.
The RM590 is available in a QFN2220-8 package with dimensions of 2.2 x 2.0 x 1.5 mm, evaluation boards are available now from our approved local distributors or online partners. It is scheduled to be added to our PLP program for long term availability.

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