Low power, low cost, wireless ECG monitor design skills

In addition to performance, reliability, low power and cost, wireless ECG monitor design must support dedicated telemetry band, so that the monitors ECG data quickly, accurately and safely transmitted to the data collector.

How to design a low-power, low cost, wireless ECG monitor? this article will give you directions.

Traditional cardiac monitor usually needs to carry record monitor, placed near the neck or wrist pocket, while wireless ECG monitoring instrument of noise and interference dramatically lower, size reduced to even can be installed on the back of the electrodes, is able to provide more accurate than traditional solutions.

This circuit cheap, and can provide diagnostic quality 1-lead ECG traces, driver leg eliminates on 60Hz notch filter needs. All of the circuit can be dressed in clothes, comfort and privacy for patients. Patient monitoring data through encryption, every few minutes automatically uploaded to the hospital, nursing institutions or conservation institutions in the field of acquisition and analysis system. The patient can be scheduled time (daily or weekly) to the doctor's Office or clinic in the uploaded information without having to remove the monitor or reposition the electrode. Wireless ECG monitor can also install the storage card, mobile phone or a local area network for data transfer. In addition to performance, reliability, low power and cost, wireless ECG monitor design must support dedicated telemetry band, so that the monitors ECG data quickly, accurately and safely transmitted to the data collector.

Solution

In North America, and wireless medical telemetry service (WMTS) frequency bands as well as other non-authorized industrial, scientific and medical (ISM) band provides dedicated spectrum, to ensure that data transfers without interference, reliable connection.

ADI's ADF7021 high performance, Narrowband ISM Transceiver IC support WMTS band and 433MHz, 868MHz and 915MHz ISM band. ADF7021 has the best of receiver sensitivity, in as-123dBm 1kbps, built-in T/R switch, VCO tank, RF/IF filter, fully automatic frequency control (AFC) and automatic gain control (AGC) circuitry. In order to extend battery life, power consumption can be set in the ADF7021 is extremely low sleep mode current consumption, reduced to A less than 0 μ.

ADF7021 and low-power microcontroller, average standby current of less than 2 μ A.

WMTS optimized radio reference design (EVAL-ADF7021DBZ6) including schematics and layout for users as wireless ECG monitor design.

AD623 is an integrated single-power amps, rail-to-rail output swing and low power consumption (3V voltage power for 1.5mW).

Its central node for common-mode signal access residues. AD8500 low power, high precision CMOS operational amplifier maximum supply current is 1 μ A maximum offset voltage 1mV, typical input offset current 1pA, rail-to-rail input and output, using 1.8V ~ 5.5V single power or ± 0.9V ~ ± 2.75V dual supply. AD8641 low power, rail-to-rail output pn junction field effect transistor (JFET) amplifier with high input impedance, high-precision performance and low-cost, input impedance greater than 681 k Ω. AD7466 is a 12-bit ADC, small package, and requires very little power, 3.6V/50 kSPS, power 480 W μ. It uses 6 Sot. For a wider dynamic range and higher signal to noise ratio design, PulSAR ADC can provide AD7685 16-bit resolution, 2.5V/100 kSPS, power consumption is 1.35mW, it uses 3mm × 3mm QFN (LFCSP) package. These scenarios (see figure below) require low-power microcontroller. Another way to achieve this signal chain solutions is the use of ADC and MCU ADuC7022 instead. ADuC7022 built-in 16-bit/32-bit MCU, chip integrates a performance up to 1MSPS ADC. ADC provides the necessary dynamic range to meet the medical standards, detection of changes in ECG waveform. ARM7 architecture including 32-bit registers so that it can perform real-time ECG signal FIR filter.