Maxim aims for clinical-grade vital signs monitoring with pulse sensor/AFE chips
Maxim already serves this market space with a number of products, primarily for the “fitness wearables” market domain. At present, a company spokesman said, that business is much greater than the corresponding delivery of product to the clinical part of the market. Now, however, Maxim sees a convergence between the two, with its “fitness” customers seeking to obtain approval (FDA in the USA) for products certified as having the performance to operate as clinical devices – yielding data that can be the basis of medical diagnosis and treatment. Examples quoted include product categories such as an ECG patch, in which the front-end signal capture and processing moves to the (potentially, consumable/disposable) skin patch; and continuous blood-glucose monitoring by non-invasive means.
The two device familes in this announcement comprise the MAX86140 and MAX86141 optical pulse oximeter/heart rate sensor ICs and the MAX30001 electrocardiogram (ECG) and bioimpedance (BioZ) analogue front end (AFE).
MAX30001 is a complete, biopotential and bioimpedance (BioZ), AFE for wearables. It has two channels; a bioimpedance (skin resistance) channel that has an excitation current source and voltage measurement connection; and an ECG input that measures the body’s own potentials. Specifications (product page here) include clinical-grade ECG data conversion of 15.9 bits ENOB with 3.1 µVPP (typ) noise for ECG; and 17 bits ENOB with 1.1 µVPP noise for BioZ applications. Power usage of 85 µW at 1.1V supply voltage (or 158 µW for BioZ operation) extends battery life in continuous monitoring. The MAX30001 is a single biopotential channel providing ECG waveforms, heart rate and pacemaker edge detection, plus a single bioimpedance channel capable of measuring respiration.
The biopotential and bioimpedance channels have ESD protection, EMI filtering, internal lead biasing, DC leads-off detection, ultra-low-power, leads-on detection during standby mode, and calibration voltages for built-in self-test. Soft power-up sequencing ensures no large transients are injected into the electrodes. Both channels also have high input impedance, low noise, high CMRR, programmable gain, various low-pass and high-pass filter options, and a high resolution analogue-to-digital converter. The biopotential channel is DC coupled, can handle large electrode voltage offsets, and has a fast recovery mode to quickly recover from overdrive conditions, such as defibrillation and electro-surgery. The bioimpedance channel includes integrated programmable current drive, works with common electrodes, and has the flexibility for 2 or 4 electrode measurements. It also has AC lead off detection. MAX30001 meets IEC60601-2-47, clinical ECG standards. Features include two parallel input channels with “voting” to detect poor contact with the subject, and therefore to validate “good signal” conditions.
MAX86140 and MAX86141 are sensor chips that can be used to measure PPG (photo-plethysmography) signals on the wrist, finger, and ear to detect heart rate, heart rate variability, and pulse oximetry. In common with other such sensor devices, the ICs drive multiple LEDs (three channels, up to six LEDs) of different wavelengths and detect blood flow through the skin; parameters such as pulse rate and blood-oxygen saturation are derived by embedded algorithms. Compared to competitive solutions, Maxim asserts, the MAX86140 and MAX86141 require less than half the power and are approximately one third smaller.
MAX86140 is available for $3.05 and MAX86141 for $3.35 (1000), in a 20-pin WLP (2.048 x 1.848 mm) and operate over the -40 to +85C operating temperature range; their MAX86140EVSYS# evaluation kit, which evaluates both MAX86140 and MAX86141, is $100.
MAX30001 costs $5.83 (1000) in a 28-pin TQFN and 30-bump WLP (2.7 x 2.9 mm); operates over the 0 to 70C range; and its MAX30001EVSYS# evaluation kit is also $100.
Maxim; www.maximintegrated.com/products/MAX86140; www.maximintegrated.com/products/MAX86141; www.maximintegrated.com/products/MAX30001
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