Microchip Technology Inc

Low Power Blood Pressure Meter Demonstration

PIC24FJ128GC010 Family

A blood pressure meter, or sphygmomanometer, is a device that is used to measure blood pressure. The meter is used with an inflatable cuff for restricting blood flow and a pump to inflate the cuff. Digital blood pressure meters typically measure both systolic and diastolic pressures by an oscillometric detection method, using a piezoelectric pressure sensor.

The Microchip Blood Pressure Meter Demonstration was implemented using the system-on-a-chip PIC24FJ128GC010 MCU. The features of this MCU are:

  • eXtreme Low Power (XLP) technology
    • 18 nA Deep Sleep mode
    • 240 nA Watch Dog Timer operation in Deep Sleep modes
    • 180 µA/MHz Run mode
  • 16-bit Delta-Sigma Analog-to-Digital Converter (ADC): 2 differential channels
  • 12-bit 10 Msps pipeline ADC: 50 channels
  • Two 10-bit 1 Msps Digital-to-Analog Converter (DAC)
  • Two operational amplifiers
  • Three comparators
  • Three voltage references
  • Charge Time Measurement Unit (CTMU)
  • USB with Device/Host/OTG support with active clock tuning (no crystal required)
  • Segmented LCD driver with charge pump

This reference design helps to develop a low-cost, low-power, handheld or portable blood pressure meter with user interface.*

System Diagram

Demonstration Highlights

  • Measures both systolic and diastolic pressures
  • Measures heart rate
  • Low overall BOM cost due to high level of integration
  • eXtreme Low Power (XLP) operation
  • Measure While Inflating (MWI) algorithm used to reduce patient discomfort
  • Utilizes the PIC24FJ128GC010's integrated Pulse-Width Modulation (PWM) module to drive the air pump's motor in fast or slow speed mode
  • Integrated LCD controller generates the data and timing control required to directly drive a static or multiplexed LCD panel
  • High-pass filter implemented with one of the PIC24FJ128GC010 MCU's integrated operational amplifiers
  • MCP1802 LDO converts the 5V or 6V main input voltage to 3.3V VDD

Battery Life

Energizer® Application Support (from the makers of Energizer batteries) did extensive testing of Microchip's Low-Power Blood Pressure Meter demonstration. From that testing they were able to estimate that the long-term battery life of the Microchip Blood Pressure Meter demonstration was 700 uses when used with four standard alkaline AAA batteries. In contrast, they also ran the same tests on five popular name-brand blood pressure meters that don't use Microchip parts. For these meters, the battery life ranged from over 500 uses down to 75 uses with four standard alkaline AAA batteries. With 700 uses, the Microchip solution demonstrated a significant increase in battery life. Additionally, Energizer found that by using their Ultimate Lithium AAA batteries in the demonstration, the number of uses increased to almost 1,200.

Resources

Downloads

Related Pages

Contact your local sales representative to see a working demonstration of the Blood Pressure Meter demo.

Development Made Easy

Start with the free download of the application note, schematics and 'C' source code that can easily be modified to your specific application needs. To download, see the Resources section.

*Microchip medical reference designs and demos are intended for evaluation and development purposes only. Use of Microchip devices in life support and/or safety applications is entirely at the buyer's risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use.

Blood Pressure Video Channel