AMS OSRAM: SFH 7018 ENABLES IMPROVED QUALITY OF HEART RATE AND BLOOD OXYGEN MEASUREMENTS FOR WEARABLES
The new SFH 7018 red/green/IR LED increases total radiant intensity by more than 40 percent over the previous generation product.
ams OSRAM released a new multi-LED package which offers more than 40 percent higher radiant intensity than the previous generation product, resulting in higher accuracy PPG (photoplethysmography) measurements in smartwatches, wristbands and other wearable devices.
The SFH 7018 features a highly reflective QFN (Quad Flat No Leads) package for significantly increased light output. In addition, an improved two-cavity design separates the green LED from the red LED and infrared (IR) LED: the spacing and optical isolation ensure that the light sources are optimally placed relative to their photodiodes and reduce interference between the green light (for heart rate measurements) and the red light and IR source (for blood oxygen saturation, or SpO2, measurements). Furthermore, the green chip does not cause the red and IR chips to fluoresce due to cross-excitation from the shorter wavelength.
The optimized form factor of the surface-mount QFN package – just 0.6 mm high – makes it easy to integrate the module into any type of wearable device. Despite its compact size, the SFH 7018 provides dual driving capability with optimized forward voltage headroom and reduced overall power consumption.
Product Picture SFH 7018A (Image Rights: ams OSRAM)
Higher radiant intensity increases the signal-to-noise ratio
The SFH 7018’s improvement in radiant intensity is dramatic: the red and IR LEDs are more than 40 percent brighter than in the existing SFH 7016, and the green LED in the SFH 7018A version of the product is 80 percent brighter, while in the SFH 7018B version, the green LED is more than twice as bright. The brightness of the SFH 7018 at each of the red, green and IR wavelengths also greatly exceeds that of today’s best-performing competing product.
Since all vital signs monitoring devices face the challenge to detect little modulations of already small light signals, the result of scattering and absorption in tissue (depending on various factors), the amount of light emitted by the LEDs strongly affects system performance. When more light is modulated by the blood flow and subsequently reaches the photodiode, signal quality improves, yielding higher accuracy and better repeatability of measurements. The SFH 7018 enables this superior performance by emitting more light into the body.
The SFH 7018 is available in two versions: SFH 7018A is optimized for low forward voltage at high currents, allowing for operation without a costly voltage booster. SFH 7018B is optimized for maximum radiant intensity.
Product Picture SFH 7018B (Image Rights: ams OSRAM)