APPLICATION NOTE 7487

Power Supply Subsystem for MAX30001-Based ECG Remote Patient Vital Sign Monitor

By: Marc Smith

Abstract:

This application note is part of a series providing guidance for its readers to implement and validate a proven switch-mode power supply circuit for use in remote vital sign monitoring devices using Maxim Biosensing Analog Front Ends (AFEs). This document focuses on a vital sign monitor using the MAX30001 ECG AFE. Within this application note, readers will find reference schematics and layout (in popular EDA and PDF formats), validation check lists, and trouble-shooting guideline.


The figure below, shows a block diagram where the MAX30001 AFE device requires two power channels to power the digital supply, analog supply, and the OVDD (Logic Interface Voltage) supply.

This subsystem passes the performance limit criteria as specified by IEC60601 201.12.4.4.106 System Noise testing.

Design Limits

Input (VBATT) Output (VDIG, VANA) Noise, RTO
ViMIN ViMAX VoMIN VoMAX VPP(max)
3.0V1 4.2V1 1.6V 2.0V 30mVPP
2.0V2 3.6V2 1.6V 2.0V 30mVPP

1: Secondary cell battery (LiPo)
2: Primary cell battery (Li coin cell)

MAX30001-Based ECG Remote Patient Vital Sign Monitor.
MAX30001-Based ECG Remote Patient Vital Sign Monitor.

Design Configuration Battery Implementation Board Area Layout Considerations
Discrete Primary (Coin Cell)
Secondary (Li & LiPo)
  • Implements separate discrete circuits
  • Integrated Secondary (Li & LiPo)
  • Uses single integrated circuit for minimal board area requirements
  • Supports secondary batteries only
  • Discrete Design Description

    This DC-DC converter design is used to regulate two output power supply rails for use in a remote patient vital sign monitor subsystem. Powered by a rechargeable lithium polymer battery or a primary Li Cell battery, this circuit provides proper line and load regulation while maintaining low output noise levels needed to preserve biosensing SNR performance.

    ECG Subsystem Using Discrete MAX38640A PS Devices.
    ECG Subsystem Using Discrete MAX38640A PS Devices.

    Key Components

    Designator Component Description
    U1 DC-DC Converter Power Converter Device (MAX38640A)
    L1 2.2μH Inductor Low ESR Inductor (Energy) Storage Component1
    C1 22μF Capacitor Low ESR Capacitor (Energy) Storage Component1

    Notes:
    1) L1 & C1 are specially selected passive components that are critical to the performance of the DC-DC converter (A.K.A., switch-mode power supply).

    1.8V SMPS Circuit Using the MAX38640A Device

    The following MAX38640A circuit illustrates typical input and output power supply levels for a properly operating Switch-Mode Power Supply (SMPS) device in remote patient vital sign monitor applications. As shown below, digital multimeters (DMM) can be used to probe the input and output ports to validate the supply voltage levels. Please note that power supply output levels can vary due to various factors such as:

    • Discharging battery
    • Changing loads (i.e., device mode changes, devices waking up from sleep mode, etc.)


    1.8VDC MAX38640A SMPS Circuit for Wearable/Healthcare Applications.

    MAX38640A Reference Design Files

    Click the following link to access the MAX38640A circuit reference design page to obtain land patterns, schematic symbols in various formats, and CAD data: MAX38640A Reference Design.

    Click the following link to access the MAX38640A Validation Data Report: Validation Data Report for Discrete SMPS Circuits.

    1.8V SMPS Circuit Validation Checklist

    Click on the following link for access to a circuit validation checklist.

    1.8V SMPS Circuit Troubleshooting Guide

    Click on the following link for access to a circuit troubleshooting guide.

    Integrated Design Description

    This DC-DC converter design is used to regulate two output power supply rails for use in a remote patient vital sign monitor subsystem. Powered by a rechargeable lithium polymer battery, this circuit provides proper line and load regulation while maintaining low output noise levels needed to preserve biosensing SNR performance.

    ECG Subsystem Using an Integrated MAX77642 PS Device.
    ECG Subsystem Using an Integrated MAX77642 PS Device.

    Key Components

    Designator Component Description
    U1 DC-DC Converter Power Converter Device (MAX77642)
    L1 2.2μH Inductor Low ESR Inductor (Energy) Storage Component1
    C1 22μF Capacitor Low ESR Capacitor (Energy) Storage Component1

    Notes:
    1) L1 & C1 are specially selected passive components that are critical to the performance of the DC-DC converter (A.K.A., switch-mode power supply).

    1.8V/1.8V SMPS Circuit Using the MAX77642 Device

    The following MAX77642 circuit illustrates typical input and output power supply levels for a properly operating Switch-Mode Power Supply (SMPS) device in wearable Medical/Healthcare applications. As shown below, digital multimeters (DMM) can be used to probe the input and output ports to validate the supply voltage levels. Please note that power supply output levels can vary due to various factors such as:

    • Discharging battery
    • Changing loads (i.e., device mode changes, devices waking up from sleep mode, etc.)


    Integrated 1.8V/1.8V MAX77642 SMPS Circuit for remote Patient Vital Sign Monitor Applications.

    MAX77642 Reference Design Files

    Click the following link to access the MAX77642 circuit reference design page to obtain land patterns, schematic symbols in various formats, and CAD data: MAX77642 Reference Design.

    Click the following link to access the MAX38640A Validation Data Report: Validation Data Report for Integrated SMPS Circuits.

    1.8V/1.8V SMPS Circuit Validation Checklist

    Click the following link for access to the circuit validation checklist.

    1.8V/1.8V SMPS Circuit Troubleshooting Guide

    Click the following link for access to the circuit troubleshooting guide.