Ben Shen
Technical Marketing Manager for Timing Products
Published: July 27, 2019

Over several decades, electronic semiconductor advances have been observed and chronicled on technology innovation, functionality enhancements, as well as component or device form factor improvement. The non-stop technology evolutions can be seen from mainframes to personal computing to smartphones, and especially more recently in wearable devices. As wearables become more ubiquitous, they are getting more powerful and smaller.

For wearables, the form factor definition has become much more varied than we could have imagined even a few years ago. For example, today we have smartwatches, smartbands, wristbands, wireless earbuds, smart devices, medical monitor/patches, and many other small designs to deliver any number of functions or services that we need.

However different, there is a common challenge across all these devices, and that is board space restriction. For a mini-computer to fit on your wrist, in your ear, or be implantable requires miniature, lightweight components with more integrated functionality.

There are still many wearable products or SiP (System in Package) modules designed with conventional discrete crystal oscillator components for their timing solution. But crystals usually occupy more board space. For instance, 1612 crystals (1.6 x 1.2 mm) are commonly used in wearable devices. The crystal requires two external capacitors, which require an additional 10 mm2 board space. Typically, wearables need three crystals, which means 30 mm2 or more. This has become too much for a standard wrist-worn device of only 200 mm2 total board size, and will only increase difficulties for the designer to include additional features.

Highly integrated timing clock generators within a very small package, such as Renesas’ MicroClock™ family have become a reliable solution to support wearable designs. With three clock outputs in a 2 x 2 mm 10-pin DFN package, any external components only need 6 mm2 board space. Designers typically see about 80% board space saving compared to the conventional crystals solution. This space-saving allows the benefit of a bigger battery design for longer runtime or the integration of more functions.

Board space comparison of designs with a programmable MicroClock clock generator vs. traditional discrete crystals

MicroClock devices can both address small form factor product design space restrictions and speed up the design process with their programmability and flexibility. These devices have many unique built-in features, including a reliable, ultra-low-power 32.768 kHz clock that can prevent common PCB board production variations with 32.768 kHz ppm accuracy. A programmable PLL offers diversified clocks for the frequency variations needed in wearable devices. Proactive Power Saving (PPS) function delivers smarter power management to save overall system power. An optional embedded crystal with factory accuracy trimming eliminates the discrete crystal oscillator initial frequency error commonly seen.

For more details about the complete MicroClock family of products, including technical documentation and samples, check out