As portable devices pursue multi-functional integration, battery life remains the core bottleneck for wearable devices and portable imaging systems. Today, smartwatches, bands, and other wearables not only need to perform PPG health monitoring (e.g., heart rate, blood oxygen) but also incorporate diverse functions. Meanwhile, portable imaging devices are becoming thinner and more compact while pursuing high-definition recording, fast autofocus, and optical image stabilization. The addition of features continuously increases power consumption, yet due to portability constraints, the built-in battery capacity cannot be significantly increased. The shortcomings of traditional power solutions are becoming increasingly apparent. Insufficient battery life has become a key factor limiting user experience and hindering industry upgrades. How to achieve longer, stable operation with limited power is a core challenge the industry urgently needs to solve.
AWINIC Electronics has launched the new ultra-low-power Buck-Boost AWP3770X series chips, comprehensively optimized in terms of quiescent current, conversion efficiency, and dynamic adaptability. It precisely solves the pain points of traditional solutions—high quiescent current, insufficient conversion efficiency, and poor dynamic adaptability—providing an efficient, stable, and low-noise voltage output solution for smart terminals.
I. PPG Power Supply Pain Points and Solutions
1. Low VF LED Necessitates Power Solution Upgrades
In wearable devices, PPG (photoplethysmography) technology is widely used for heart rate and blood oxygen monitoring. To further reduce overall device power consumption, the industry is gradually adopting LEDs with lower forward voltage (VF), reducing the operating voltage of PPG modules from the traditional 4.5V to 3.5V. However, the fully charged voltage of a watch's built-in lithium battery is about 4.2V, significantly higher than the module's actual power supply requirement. Traditional Boost circuits cannot step down voltage, failing to meet the wide-voltage power supply requirement that needs both step-down and step-up capabilities.
The Buck-Boost architecture, which offers both step-up and step-down capabilities, thus becomes a more suitable choice. It can flexibly adjust the output voltage based on the battery's remaining charge, ensuring stable operation across the entire battery range, perfectly matching the power supply requirements of low VF LEDs.
2. Battery Life Pressure from Continuous Lighting and Solutions
PPG functionality relies on the cooperation of LED illumination and photodiode signal reception. Even if LEDs are lit intermittently at low frequencies, the accumulated power consumption over long-term wear remains high, directly limiting wearable device battery life. Additionally, the instantaneous current surge each time the LED lights up can easily cause supply voltage droop. Given PPG sampling's high precision, voltage droop can lead to distorted sampling data, forcing the system to extend lighting time to ensure accurate data sampling. Furthermore, after load transient stabilization, the supply ripple must remain highly consistent over multiple sampling periods; significant ripple differences directly degrade sampling data consistency.
Thus, PPG presents two core challenges for the power supply:
First, the load transient response speed must be fast.
Second, the ripple consistency after load transient stabilization must be good. These two factors directly determine the battery life and monitoring accuracy of wearable devices.
Addressing these stringent requirements, the AWP3770X series demonstrates excellent performance: load transient recovery time is controlled within 10μs, outperforming the industry norm of over 15μs; ripple deviation after multiple transients remains within 10mV, significantly better than the typical 25mV+ seen in competing products. With fast response and excellent ripple control, this solution effectively improves battery life and monitoring accuracy, highly matching the power supply needs of PPG applications.
Figure 1 AWP3770X Dynamic Transient Results
II. VCM Power Supply Pain Points and Solutions
1. Energy Waste from Fixed-Voltage Supply and Solutions
In imaging systems, traditional VCM (Voice Coil Motor) solutions often use a fixed high-voltage LDO power supply. Since the VCM load impedance is fixed, its operating current changes dynamically with AF (Auto Focus)/OIS (Optical Image Stabilization) conditions. In low-current operating scenarios, the voltage actually required by the VCM should ideally decrease accordingly, but the fixed high-voltage supply continues to output the rated high voltage, causing excess voltage to be converted into wasted power. This not only increases system heat but also directly shortens device battery life.
Therefore, adopting a dynamic voltage adjustment scheme, where the supply voltage matches the motor's operating current in real-time to fundamentally eliminate energy waste, has become an inevitable trend in VCM power supply design.
Figure 2 Traditional VCM Power Supply Scheme
Targeting the energy efficiency bottleneck of traditional fixed-voltage VCM supplies in imaging systems, AWINIC introduces the AWP37702 Buck-Boost dynamic power supply chip, providing an efficient and easy-to-implement solution. Compared to traditional solutions, dynamic voltage supply offers two core advantages:
On one hand, the supply voltage can be dynamically adjusted based on the motor's actual operating current, reducing wasted power at the source. The chip follows AF/OIS control signals in real-time, flexibly adjusting output voltage to precisely match the motor's instantaneous current demand, avoiding energy waste caused by fixed high voltage. This reduces power consumption, lowers heat generation, and extends battery life without affecting autofocus speed or stabilization performance.
On the other hand, the Buck-Boost switching architecture is significantly more efficient than traditional LDOs. Traditional LDOs use linear step-down, resulting in low efficiency and significant heat generation when the voltage difference is large. The AWP37702 uses a switching Buck-Boost architecture, achieving higher power conversion efficiency. For example, under 4V to 3.3V/0.2A conditions, efficiency can reach 95%, far higher than the roughly 82.5% of traditional LDOs.
Actual tests show that compared to traditional fixed-voltage solutions, the VCM dynamic voltage supply based on the AWP37702 achieves an average power saving of about 33%, making it an ideal choice for next-generation imaging system power design.
Figure 3 VCM Dynamic Voltage Supply Scheme
Figure 4 Power Consumption Comparison: Traditional VCM Supply vs. Dynamic Voltage Supply
AWP3770X Product Introduction
· Input Voltage Range: 2.2V ~ 5.5V
· Output Voltage Range: 2.025V ~ 5.2V (AWP37701Z) / 1.4V ~ 4.575V (AWP37702)
· Ultra-Low Quiescent Current: 2.8μA
· Ultra-Low Shutdown Current: 0.3μA
· Supports Dynamic Voltage Scaling Control
o AWP37701Z Slew Rate: 1V/ms, 2.5V/ms, 5V/ms, 10V/ms
o AWP37702 Slew Rate: 2V/ms, 5V/ms, 10V/ms, 20V/ms
· Auto PFM Mode and Forced PWM Mode
· Up to 1MHz I2C Interface (supports 1.2V I/O level)
· Maximum Continuous Output Current:
o Up to 0.8A at VIN ≥ 2.2V, VOUT = 3.5V
o Up to 1A at VIN ≥ 2.5V, VOUT = 3.5V
o Up to 1.5A at VIN ≥ 3.3V, VOUT = 3.5V
· Miniaturized Solution: WLCSP 1.3mm×1.3mm-9B chip + 0603 inductor (1.6mm×0.8mm), capable of meeting 1.5A load requirements.
Figure 5 AWP3770X Package Information
Figure 6 AWP3770X Typical Application Diagram
From precision PPG power supply for wearables to dynamic voltage scaling for VCM in imaging systems, AWINIC's AWP3770X series Buck-Boost chips deliver lower quiescent current, faster transient response, and higher conversion efficiency, effectively solving the dual challenges of battery life and performance in portable devices. As end products continue to trend towards thinner, lighter, and more multi-functional designs, efficient power solutions have become key to enhancing product competitiveness. Moving forward, AWINIC will continue to deeply explore power technologies, providing better components and solutions to drive sustained momentum for wearables, imaging systems, and more smart terminal applications.
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