Ultra-Low Power, High Precision, Compact Size! 3PEAK's Continuous Glucose Monitoring System (CGM) Solution

2024-04-26

Traditional Blood Glucose Monitors (BGMs) involve frequent finger pricking for blood samples, causing discomfort and posing a potential risk of infection. Moreover, BGMs have blind spots for glucose monitoring and cannot effectively monitor glucose levels at night. While these issues may be manageable for patients with type 2 diabetes, they are significantly more troublesome for those with type 1 diabetes.

To address these challenges, CGMs have emerged. CGMs greatly improve upon two key issues found with traditional BGMs. By utilizing a subcutaneously implanted sensor, they offer a compact and comfortable solution. CGMs can continuously monitor glucose levels for 7 to 14 days. A common product design is shown in the picture below.

3PEAK Products for CGM Applications

Glucose measurement in CGMs is based on extracting glucose from the blood, which reacts with glucose oxidase on test strips to generate a measurable current. These products are typically powered by a single button cell battery, requiring at least two weeks of continuous operation. This necessitates a high demand for low power consumption in the built-in device.

Ultra-Low Power Operational Amplifiers

CGM devices are categorized into integrated Analog Front Ends (AFEs) and discrete solutions. The latter requires an operational amplifier for I-V conversion amplification and to apply an excitation power source, facilitating a current flow induced by an enzymatic reaction. The current generated by this reaction typically ranges from a few nanoamps to tens of nanoamps, necessitating an operational amplifier with an Input Bias Current (Ibias), paired with megaohm-level I-V conversion resistors. Considering battery life, power consumption needs to be minimized. Additionally, due to the product's compact size, a smaller package is preferred. Depending on the electrode configuration, operational amplifiers typically require two to four channels.

For varying resolution requirements, 3PEAK recommends its ultra-low power devices TPA5512 and TP2112, both supporting rail-to-rail input and output. The TPA5512 device consumes only 650-nA, has a maximum Offset Voltage (Vos) of 30-uV, a temperature drift coefficient of 0.025-uV/°C, and an Ibias of only 20-pA, making it highly suitable for precise CGM applications. It supports a supply range as low as 1.7-V, catering to 1.8-V battery-powered applications. Notably, TPA5512 offers various package options (SOIC-8, MSOP-8, and DFNX2-8), with the DFN package being ideal for space-sensitive applications. If the requirements for Vos are moderate (for instance, calibrated through software), the TP2112 device can be considered. It has a power consumption of only 500-nA and an Ibias as low as 1-pA. Available in SOIC-8 and MSOP-8 packages, it offers exceptional value for applications.

TPA5512 Specifications

Power Supply Range: 1.7 V to 3.6 V
Number of Channels: 2
Typical Quiescent Power: 650 nA
Maximum Vos: 30 μV
Temperature Drift Coefficient of Vos: 0.025 μV/°C
Typical Ibias: 20 pA
Bandwidth and Slew Rate: 9 kHz and 3 mV/μs
Noise Indicator: 354 nV/√Hz @ 100Hz
Package: SOIC-8, MSOP-8, DFN2X2-8

TP211x Specifications

Power Supply Range: 1.8V to 5.5V
Typical Quiescent Power: 500 nA
Maximum Vos: 1.5 mV
Temperature Drift Coefficient of Vos: 0.4 μV/°C
Typical Ibias: 1 pA
Bandwidth and Slew Rate: 10 kHz and 6 mV/μs
Package: SOIC-8, MSOP-8

Ultra-Low Power Boost Devices

As batteries deplete during use, their output voltage decreases. A boost device is necessary to stabilize voltage output and extend battery life. The introduction of batteries as low as 1.5-V has made boost devices even more essential for powering MCUs.

The TPQ05100 ultra-low-power boost chip from 3PEAK is a synchronous boost converter suitable for low-voltage systems. With an input voltage range of 0.9-V to 5.5-V, it can support even lower input voltages. The output voltage is adjustable from 2.5-V to 5.5-V. Its unique small packages, QFN2X2-6 and WLCSP (0.8 mm × 1.2 mm), are highly suitable for space-constrained applications.

Due to the continuous dormancy of CGM for the majority of time, it only operates intermittently at a fixed frequency. This implies that the battery-powered load operates in PWM form rather than in a continuous mode, as illustrated below.

The device is in sleep mode for over 99% of the time, necessitating a high demand for efficient quiescent current to extend battery lifespan. During this time, the load is minimal, measured in microamperes, but spikes to milliampere levels for less than 1% of the time. Such high-current pulses often result in significant surge currents, affecting battery capacity and longevity. The TPQ05100 includes an internal current-limiting circuit to effectively reduce surge currents during these pulses, thereby enhancing battery life. Despite the pulses lasting only milliseconds, including pulse setup and sampling times, shortening these durations can significantly prolong battery usage. The TPQ05100's rapid transient response efficiently minimizes pulse setup times, leading to faster sampling and reduced current consumption.

TPQ05100 Specifications

Power Supply Range: 0.9 V to 5.5 V
Output Range: 2.5 V to 5.5 V (fixed output versions available)
Maximum Output Current: 600 mA
Typical Quiescent Current: 260 nA
Package: WLCSP-6, DFN2X2-6

Ultra-Low Power Low Dropout Regulator (LDO)

The battery's voltage output fluctuates significantly. Directly powering operational amplifiers from the battery can affect their output precision. For this scenario, 3PEAK recommends its ultra-low power LDO, the TPL710. This low-voltage LDO boasts an extremely low quiescent current and quick response to dynamic loads. It stabilizes with just a 2.2-μF ceramic capacitor and features current limiting and over-temperature protection, significantly improving product reliability. With EN control, it outputs fixed voltages between 1.0-V and 3.6-V, available in various packages, including SOT23-3, SOT23-5, and the compact DFN1X1-4.

TPL710Fxx Specifications

Power Supply Range: 2.4 V to 6.0 V
Maximum Output Current: 200 mA
Typical Output Accuracy: 1%
Typical Quiescent Current: 1.4 μA
Dropout Voltage: 170 mV @ 200 mA
PSRR: 54 dB @ 1 kHz

As the number of patients with diabetes continues to increase each year, the demand for comfortable CGM devices is also on the rise. These devices, with their unique medical attributes, require both measurement accuracy and reliability. 3PEAK, with years of dedication in the signal chain and power supply domains, leads in performance and strict quality control. Boasting a comprehensive delivery system and partnerships with key domestic healthcare clients, 3PEAK is a trusted partner you can rely on.