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Pulse Oximeter | Cypress Semiconductor

Block Diagram

PSoC programmable analog & digital resources integrate everything shown in light blue below. Click on the colored blocks to view or sample the recommended PSoC Components.

 

The flexibility of PSoC allows you to customize each colored block, or PSoC Component, to meet your design requirements through the easy-to-use PSoC Creator Software IDE.  These Components are available as pre-built, pre-characterized IP elements in PSoC Creator.

Design Considerations

A Pulse Oximeter is a non-invasive device for measuring the percentage of arterial blood (or hemoglobin) that is saturated with oxygen. This device can also measure heart rate. Pulse Oximeters are used in medical, sports training and home appliance applications. Knowing the percentage of hemoglobin that is saturated with oxygen is important to provide anesthesia, to determine the effectiveness of a patient's respiratory system, as well as help to diagnose various illnesses.

The principle of operation of a Pulse Oximeter is based on measuring the absorption of red and infrared light that passes through a patient's finger or ear lobe by utilizing light sensors. Hemoglobin that transports oxygen (oxy-hemoglobin) absorbs infrared wavelength (800-940 nm) of light and hemoglobin that does not transport oxygen (deoxy-hemoglobin), absorbs visible RED wavelength (600-700 nm) of light. Backgrounds such as fluid, tissue and bone are factored out of the measurement by monitoring the steady state of absorption from bone, tissue, venous blood and arterial blood. LEDs are used as the light source and are sequentially pulsed at a fast rate. During a heartbeat, blood volume increases and this AC component of the photodetector's current is used to calculate the absorption of oxy- and deoxy-hemoglobin.

PSoC enables a scalable one chip pulse oximeter solution that flexibly integrates all the basic and advance requirements of a pulse oximeter. PSoC can also enable more advanced features for innovating Pulse Oximeters including USB, Graphics Display, and CapSense buttons. Finally, PSoC can also integrate numerous vital sign functions such as Blood Pressure Monitor, IR Thermometer, and Pulse Oximeter into a single chip solution.
 

Application Notes

  • AN52927 demonstrates how easy it is to drive a segment LCD glass using the integrated LCD driver in PSoC 3 and PSoC 5LP. This application note gives a brief introduction to segment LCD drive features and provides a step-by-step procedure to design Segment LCD applications using the PSoC Creator tool.

  • AN57821 introduces basic PCB layout practices to achieve 12- to 20-bit performance for the PSoC 3, PSoC 4, and PSoC 5LP family of devices.

  • AN58304 provides an overview of the analog routing matrix in PSoC® 3 and PSoC 5LP. This matrix is used to interconnect analog blocks and GPIO pins. A good understanding of the analog routing and pin connections can help the designer make selections to achieve the best possible analog performance. Topics such as LCD and CapSense routing are not covered in this application note.

  • AN58827 discusses how internal trace and switch resistance can affect the performance of a design and how these issues can be avoided by understanding a few basic details about the PSoC® 3 and PSoC 5LP internal analog architecture.

  • This application note describes how to configure the PSoC® 3 and PSoC 5LP IDACs as a flexible analog source. It presents different approaches for using the IDACs in applications, and discusses the advantages and disadvantages of the topologies presented. This application note will: help you to understand compliance voltage and why it is important; explain how to generate an “any range” or “any ground” VDAC; describe an implementation for a multiplying VDAC; give details on how to build a rail-to-rail low-output impedance 9-bit VDAC from a single IDAC, an opamp, and a resistor; and provide information on how to build a current scaling circuit with an opamp and two resistors.

  • AN60590 explains diode-based temperature measurement using PSoC® 3, PSoC 4, and PSoC 5LP.

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Software and Drivers

  • PSoC Creator

    PSoC Creator is a state-of-the-art software development IDE combined with a revolutionary graphical design editor to form a uniquely powerful hardware/software co-design environment.

  • PSoC Designer

    PSoC Designer is the revolutionary Integrated Design Environment (IDE) that you can use to customize PSoC to meet your specific application requirements. PSoC Designer software accelerates system bring-up and time-to-market.