Ultra-thin sensor for blood-oxygen monitoring fits tiny devices

ams has claimed the industry’s thinnest sensor designed for blood oxygen saturation (SpO2) measurement. The new blood-oxygen monitoring sensor enables OEMs of small consumer devices such as earbuds, smart watches, and wristbands to add the capability for remote monitoring.

The AS7038RB  SpO2 sensor also can be used in medical devices such as patches and oximeters. Thanks to the sensor’s high performance it is suitable for applications in remote diagnostic equipment, such as disposable patches used for SpO2 and electro-cardiogram (ECG) measurement in hospital emergency rooms. The benefit for both medical teams and patients is the greater flexibility to choose how, where and when measurements of these vital signs are taken using non-invasive methods for fast response, said ams.

The sensor, housed in a 3.7 x 3.1 x 0.65-mm package, integrates a highly sensitive photo-diode, four LED drivers, an analog front end, and a sequencer. It is supplied with application software for SpO2 and heart rate measurement. The analog front end also supports concurrent ECG measurement complying with the requirements of the IEC 6060-2-47 medical standard.

The device offers high accuracy with the SPO2 measurements closely matching the outputs from medical-grade pulse oximeters used in hospital testing facilities, according to the company. This is thanks in part due to the unique on-wafer interference filter technology developed by ams. The filter enables the AS7038RB to capture optical signals in the 590 nm-710 nm and near infrared (800 nm-1050 nm) wavelength bands of interest for SpO2 measurement, while blocking interference from ambient light at other wavelengths.

The high-sensitivity photodiode, which has a large light-sensitive area of 2.5 mm2, produces a very high optical signal-to-noise ratio, said ams, which eases implementation in optically challenging applications such as disposable chest patches, wristbands, and smart watches.

In addition, the provision for up to four external LEDs enables designers to place the LEDs in the best position for the application, such as at the wrist, chest, forehead, finger, etc. The integrated LED drivers also help designers balance system power consumption and measurement performance by enabling the adjustment of the drive current. This helps extends run-time between battery charges.

ams also introduced the AS7038GB, a version of the sensor with peak sensitivity at the 525 nm (green) wavelength for use in heart rate (HRM) and heart rate variability (HRV) measurement. A modular version, the AS7030B HRM/HRV sensor, integrates two 535-nm LEDs in a single package measuring 3.55 x 6.2 x 1mm.

The AS7038RB for blood-oxygen monitoring is sampling now. Mass production is scheduled in October.