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 favoured 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 buck-boost regulator based on an innovative architecture that’s optimised for 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 minimise 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 favourable conditions. The MAX20345 is available in a 56-bump, 0.4mm pitch, 3.37mm x 3.05mm wafer-level package (WLP).
- Superior Performance for Optical Systems: the integrated buck-boost regulator provides the low ripple at high frequency that will not interfere with optical measurements. These short settling times support the high-sensitivity optical-sensor measurements on wearables.
- Extended Battery Life: regulators with nanoPower quiescent current reduce sleep and standby power, which in turn extends battery runtime and allows for smaller battery size. High-efficiency regulators preserve battery energy during active states.
- Small Footprint: by eliminating multiple discrete components, the MAX20345 provides a sophisticated power architecture for space-constrained wearable and IoT designs.