PMIC keys on optical measurement sensitivity for wearable fitness/health apps

Designers of always-on wearable and IoT devices now have the ability to extend battery runtime while shrinking form factor with the latest tiny, highly integrated power-management IC (PMIC) from Maxim Integrated Products, Inc.  The ultra-low-power MAX20345 integrates a lithium charger and debuts a unique architecture that optimizes the sensitivity of optical measurements for wearable fitness and health applications.

In wearables, optical-sensing accuracy is impacted by a variety of biological factors unique to the user. Designers have been striving to increase the sensitivity of optical systems, in particular, the signal-to-noise ratio (SNR), to cover a broader spectrum of use cases. Traditional low-quiescent-current regulators favored in wearable applications come with tradeoffs that degrade SNR on the wrist, such as high-amplitude ripple, low-frequency ripple and long-settling times. Some designers have even turned to high-quiescent-current alternatives to overcome these drawbacks, but they must deal with increased power consumption, which reduces battery runtime or requires a larger battery. The MAX20345 features a first-of-its-kind buck-boost regulator based on an innovative architecture that’s optimized for highly accurate heart-rate, blood-oxygen (SpO2) and other optical measurements. The regulator delivers the desired low-quiescent-current performance without the drawbacks that degrade SNR and, as a result, can increase performance by up to 7dB (depending on measurement conditions).

The MAX20345 is also the latest in a line of ultra-low-power PMICs for small wearables and IoT devices that help raise efficiency without sacrificing battery runtime. To meet these needs, the MAX20345 integrates a lithium-ion battery charger; six voltage regulators, each with ultra-low quiescent current; three nanoPower bucks (900nA typical) and three LDO regulators with ultra-low quiescent current (as low as 550nA typical).  Two load switches allow disconnecting of system peripherals to minimize battery drain. Both the buck-boost and the bucks support dynamic voltage scaling (DVS), providing additional power-saving opportunities when lower voltages can be deployed under favorable conditions. The MAX20345 is available in a 56-bump, 0.4mm pitch, 3.37mm x 3.05mm wafer-level package (WLP).