ADI公司的低成本無線ECG Holter監(jiān)視器解決方案主要采用12位精密模擬微控制器ADuC7022, 高性能ISM頻段FSK/ASK收發(fā)器 ADF7022, 低成本儀表放大器AD623, 微功耗精密CMOS運算放大器AD8500和低功耗JFET放大器AD8641等器件.本文介紹了典型的單通道心電圖方框圖, 低功耗低成本無線ECG Holter 監(jiān)視器方框圖以及主要器件的主要特性和應(yīng)用電路.
The ECG signal is characterized by six peaks and valleys labeled with successive letters of the alphabet P, Q, R, S, T, and U.
圖1.心電圖(ECG)的信號波形
圖2. 典型的單通道心電圖方框圖
Awireless Holter monitor–small enough to fit on the back side of an electrode–provides more accurate signals than traditional designs because noise and interference are greatly reduced. The circuit is inexpensive and capable of providing diagnostic-quality 1-lead ECG traces. A driven leg eliminates the need for a 60 Hz notch filter. Depending on the frequency band used, the transceiver (the ADF702x is shown below) and its surrounding circuitry will change. Patient comfort and privacy is greatly improved because all circuitry can be worn under clothing.
圖3.低功耗低成本無線ECG Holter 監(jiān)視器方框圖(1)
圖4.低功耗低成本無線ECG Holter 監(jiān)視器方框圖(2):ADuC7022替代AD7466+MCU
主要元件性能介紹:
ADUC7022: Precision Analog Microcontroller, 12-Bit Analog I/O, ARM7TDMI® MCU
The ADuC7019/20/21/22/24/25/26/27/28 are fully integrated, 1 MSPS, 12-bit data acquisition systems incorporating high performance multichannel ADCs, 16-bit/32-bit MCUs, and Flash/EE memory on a single chip.
The ADC consists of up to 12 single-ended inputs. An additional four inputs are available but are multiplexed with the four DAC output pins. The four DAC outputs are only available on certain models (ADuC7020 and ADuC7026). However, in many cases where the DAC outputs are not present, these pins can still be used as additional ADC inputs, giving a maximum of 16 ADC input channels. The ADC can operate in single-ended or differential input modes. The ADC input voltage is 0 V to VREF. A low drift band gap reference, temperature sensor, and voltage comparator complete the ADC peripheral set.
Depending on the part model, up to four buffered voltage output DACs are available on-chip. The DAC output range is programmable to one of three voltage ranges.
The devices operate from an on-chip oscillator and a PLL generating an internal high frequency clock of 41.78 MHz. This clock is routed through a programmable clock divider from which the MCU core clock operating frequency is generated. The microcontroller core is an ARM7TDMI, 16-bit/32-bit RISC machine, which offers up to 41 MIPS peak performance. Eight kilobytes of SRAM and 62 kilobytes of nonvolatile Flash/EE memory are provided on-chip. The ARM7TDMI core views all memory and registers as a single linear array.
ADuC7022應(yīng)用:
Industrial control and automation systems
Smart sensors, precision instrumentation
Base station systems, optical networking
圖5.ADuC7026功能方框圖
http://www.analog.com/static/imported-files/data_sheets/ADUC7019_7020_7021_7022_7024_7025_7026_7027_7028.pdf
High Performance, ISM Band, FSK/ASK Transceiver IC ADF7020
The ADF7020 is a low power, highly integrated FSK/ASK/OOK transceiver designed for operation in the license-free ISM bands at 433 MHz, 868 MHz, and 915 MHz, as well as the proposed Japanese RFID band at 950 MHz. A Gaussian data filter option is available to allow either GFSK or G-ASK modulation, which provides a more spectrally efficient modulation. In addition to these modulation options, the ADF7020 can also be used to perform both MSK and GMSK modulation, where MSK is a special case of FSK with a modulation index of 0.5. The modula-tion index is calculated as twice the deviation divided by the data rate. MSK is spectrally equivalent to O-QPSK modulation with half-sinusoidal Tx baseband shaping, so the ADF7020 can also support this modulation option by setting up the device in MSK mode.
ADF7020主要特性:
Low power, low IF transceiver
Frequency bands
431 MHz to 478 MHz
862 MHz to 956 MHz
Data rates supported
0.15 kbps to 200 kbps, FSK
0.15 kbps to 64 kbps, ASK
2.3 V to 3.6 V power supply
Programmable output power
−16 dBm to +13 dBm in 0.3 dBm steps
Receiver sensitivity
−119 dBm at 1 kbps, FSK
−112 dBm at 9.6 kbps, FSK
−106.5 dBm at 9.6 kbps, ASK
Low power consumption
19 mA in receive mode
26.8 mA in transmit mode (10 dBm output)
−3 dBm IIP3 in high linearity mode
On-chip VCO and fractional-N PLL
On-chip 7-bit ADC and temperature sensor
Fully automatic frequency control loop (AFC) compensates for ±25 ppm crystal at 862 MHz to 956 MHz or±50 ppm at 431 MHz to 478 MHz
Digital RSSI
Integrated Tx/Rx switch
Leakage current of <1 μA in power-down mode
ADF7020應(yīng)用:
Low cost wireless data transfer
Remote control/security systems
Wireless metering
Keyless entry
Home automation
Process and building control
Wireless voice
圖6. ADF7020方框圖
圖7.ADF7020應(yīng)用電路
http://www.analog.com/static/imported-files/data_sheets/ADF7020.pdf
AD623: Single Supply, Rail-Rail, Low Cost Instrumentation Amplifier
The AD623 is an integrated single-supply instrumentation amplifier that delivers rail-to-rail output swing on a 3 V to 12 V supply. The AD623 offers superior user flexibility by allowing single gain set resistor programming and by conforming to the 8-lead industry standard pinout configuration. With no external resistor, the AD623 is configured for unity gain (G = 1), and with an external resistor, the AD623 can be programmed for gains up to 1000.
The AD623 holds errors to a minimum by providing superior ac CMRR that increases with increasing gain. Line noise, as well as line harmonics, are rejected because the CMRR remains constant up to 200 Hz. The AD623 has a wide input common-mode range and can amplify signals that have a common-mode voltage 150 mV below ground. Although the design of the AD623 was optimized to operate from a single suppl
