Maxim’s PMIC Rocks the Hearables Market, Slashing BoM by 40% and Bumping Battery Life 20%April 08, 2020 by Gary Elinoff
Designing hearables can be tricky enough, considering the constraints on power, space, electrical noise, and heat dissipation. Maxim says they're leveling up a new PMIC for the job.
When designing hearables and wearables, power efficiency, space savings and controlling heat dissipation and electrical noise are especially critical factors.
The MAX77654 SIMO PMIC in wearables and hearables. Image (modified) used courtesy of Maxim Integrated
Maxim Integrated claims that the MAX77654 reduces the BoM count by up to 40% while at the same time extending battery life by 20%.
The MAX77654 is a single input, multiple output (SIMO) power management IC (PMIC) that replaces three buck-boost converters, each with its own separate inductor with one converter featuring only a single inductor.
Maxim Integrated also says the unit reduces system board temperature by a full 20℃ when compared to other single inductor solutions. Moreover, the device’s output voltage ripple is less than 20 mV peak to peak.
Maxim's History With SIMO PMICs
Maxim has a long history of commitment to PMICs optimized for small lithium-ion batteries in wearable devices. Several years ago, we discussed earlier iterations of Maxim's PMIC family, which also included a SIMO regulator for longer battery life. The MAX77654 is the latest expression of longstanding experience and expertise.
As stated by Karthi Gopalan, Maxim's director of mobile solutions, “Maxim Integrated's breakthrough scalable SIMO PMIC, MAX77654, offers the smallest form factor solution with the highest system efficiency.”
She goes on to state that “The MAX77654 SIMO PMIC frees up board real estate to pack value-add modules such as voice commands, payment, GPS receivers, biometrics, gesture control, 3-D recognition, and camera.”
Basic Features of the MAX77654
As illustrated below, the single inductor PMIC provides three separately programmable power rails. It features two 100 mA low dropout regulators (LDO) for ripple rejection. These also serve as load switches to disconnect power from external blocks when applicable, saving power.
Simplified block diagram of the MAX77654. Image used courtesy of Maxim Integrated
The unit can also safely charge the LiBs—a central design aspect of hearable devices. Three general-purpose I/O’s (GPIO) enable the monitoring of internal voltage and current values through an external ADC. The internal working of the PMIC can be further monitored and controlled via a bidirectional I2C interface.
There are also a variety of factory programmable options that extend the MAX77654’s direct applicability to a variety of OEM specifications.
Big Power, Little Size
The MAX77654 can support output voltage ranges of 0.8 V to 5.5 V on all three SIMO channels. The device features a shutdown current of 0.3 μA for all three channels; the LDOs offer 6 μA of operating current.
The battery charging circuitry is appropriately optimized for the small LiBs that will be internal to hearing aids.
The MAX77654 is available in a 6.52 mm2 wafer-level package. Maxim Integrated claims that, with the necessary external components such as the inductor and several capacitors, a total solution size of 29.7 mm2 is possible.
In addition to its targeted applications of hearables and wearables, the MAX77654 will also find use in:
- Fitness and health devices
- Security and safety monitors
- Sensor nodes
- IoT devices
- Bluetooth devices
- Wireless speakers
Getting to Market Faster
Maxim Integrated offers the MAX77654EVKIT to allows designers to probe the capabilities of the MAX77654. The kit includes the SIMO buck-boost regulator, smart battery charger, analog multiplex, and I2C controller.
The MAX77654EVKIT evaluation kit. Image used courtesy of Maxim Integrated
The MAX77654 evaluation kit also includes GUI-based Windows software and a register-based interface to allow users to explore all the MAX77654’s varied features.
Around the Industry
When it comes to hearables, several other suppliers around the industry approach the design challenges of these tiny devices from a different vantage point.
NXP, for instance, offers its NxH2280 hearable solution, which works through near-field magnetic induction and serves to eliminate the wire that connects two earbuds. A solution of this nature is necessary because Bluetooth generally can only hit one target, not two.
Typical application circuit of TPS65135. Image used courtesy of Texas Instruments
This device is illustrated as another example of a PMIC SIMO unit. It’s current output capacities are higher than what would generally be relevant for a hearing aide.
Featured image (modified) used courtesy of Maxim Integrated
What are the design challenges you face with hearable or wearable devices? How do you surmount those challenges? Share your experiences in the comments below.