Low-Profile Passive Components Push Boundaries
Ultra-low-profile inductors and capacitors from Murata and TDK are pushing the limits for component density and impacting automotive safety and wearable applications.
Passive components like capacitors, inductors, and transformers are essential to power and other circuit designs, and the size and height of these components can significantly impact the form factor and performance of the end application.
LLC series multi-layer ceramic capacitors. Image used courtesy of Murata
Murata Manufacturing Co. has released the LLC series of 1 µF multilayer ceramic capacitors designed for automotive applications. The capacitors have a reversed termination for low equivalent series inductance (ESL) and, according to Murata, are the smallest in the world, with a footprint of 0.5 mm x 1.0 mm and a height profile of just 0.18 mm.
The small size of the capacitors allows for more flexibility in circuit board placement, including backside locations closer to the die, allowing for effective decoupling of processor power rails with fewer components.
Another notable product is the PLEA85 series from TDK Corporation, a family of high-efficiency power inductors in chip-scale packaging (CSP) with a height profile of only 0.55 mm. The inductors are designed for power conversion circuits in wearable and other battery-powered devices that require a small form factor and high efficiency.
Small, Low-ESL Ceramic Capacitors
To achieve the low height profile for the LLC series, Murata uses a proprietary, high-precision lamination technology that can form very thin layers within the capacitor. The result is up to a 20% reduction in component height compared to similar specified capacitors.
Using a reversed termination construction, LLC series capacitors have a thicker and shorter high-frequency conduction path that results in a lower ESL.
Reversed-type construction reduces capacitor ESL. Image used courtesy of Murata
The small form factor of the LLC capacitors allows them to fit into smaller spaces within the PCB layout, including the backside of the boards. According to Murata, the combined size and low ESL of the LLC series allows for a significant reduction in the total number of coupling capacitors required in a typical supply decoupling application.
LLC series reduces the number of coupling capacitors. Image used courtesy of Murata
The LLC series is AEC-Q200-compliant for automotive use and is designed for low-voltage (up to 4 VSX) processor supply decoupling applications in advanced driver assistance visual, radar, and lidar systems.
Low-Profile Chip Scale Inductor
According to TDK, with a height of only 0.55 mm, the PLEA85 series has the lowest profile of any comparable power inductor in the industry. The ultra-low profile is attributed to TDK’s thin-film processing techniques. The company’s recently developed low-loss magnetic material contributes to the device’s high efficiency for extended battery life.
PLEA85 low-profile CSP inductor. Image used courtesy of TDK
The bottom electrodes of the PLEA85 are designed to extend up the sides of the package to form an L shape. This design helps with reliable placement and improves terminal strength in high-density, surface-mount layouts typical of wearable and other small form factor devices.
Power Management for Smartwatches and Wearables
The size and efficiency of the PLEA85 series make it ideal for the boost power conversion circuits that are used to step up the battery voltage for display, audio, and other auxiliary loads in wearable devices like smartwatches and stereo (TWS) earphones.
The inductor is often the highest profile component in a switch-mode power conversion circuit, so reducing the height of this key component will significantly impact the size and shape of a smartwatch or other wearable.
Boost converter with inductor to power wearable loads. Image used courtesy of TI
And, while wearable devices are getting smaller and lighter, the demand for more power with fewer losses only increases as feature sets and capabilities expand.
The PLEA85 began volume production this past October and is available in three models with nominal inductances up to 2.2 µH and rated for load currents as high as 700 mA.