Automatic external defibrillators (AEDs) monitor a person's heart rhythm and deliver a defibrillation pulse if the person experiences ventricular fibrillation or fast ventricular tachycardia. ECG-analysis algorithms used to identify heart rhythms and abnormalities require reliable, high performance circuitry. Yet, this equipment must be compact while maintaining low power usage and a competitive price.

Low Cost, Low Power, High Performance AED

The AD8224 precision, dual-channel, JFET input instrumentation amplifier has a minimum common-mode rejection ratio (CMRR) of 94 dB at dc and a minimum CMRR of 84 dB at 10 kHz for G = 10. Maximum input bias current is 25 pA and typically remains below 300 pA over the entire industrial temperature range. Despite the JFET inputs, the AD8224 typically has a noise corner of only 10 Hz. It draws 750 μA of quiescent current per amplifier. It is available in a 16-lead LFCSP requiring the same board area as a typical single in-amp yet doubling the channel density.

The AD7685 is a 16 bit, 250 kSPS, successive approximation analog-to-digital converter. Power scales linearly with throughput. The AD7685 consumes 15 mW at 5 V and draws less power at lower data rates. With a signal-to-noise ratio of 91.5 dB, the AD7685 interfaces with a SPI-compatible port, and is available in 10-lead MSOP and LFCSP (QFN) packaging.

Analog Devices' precision analog microcontrollers combine precision analog functions, such as high resolution ADCs and DACs, a voltage reference, and temperature sensor, with an industry-standard microcontroller and flash memory. For example, the ADuC7022 ARM7TDMI integrates 62 kB flash, 8 kB SRAM, and a host of on-board peripherals including a multichannel 1 MSPS, 12-bit analog-to-digital converter, four 12-bit voltage output digital-to-analog converters, and 3-phase PWM–all of this and more is available in a 6 mm × 6 mm, 40-lead LFCSP package.

As an alternative, the Blackfin® processor enables the integration of signal processing and microcontroller functions in a single device. This functionality enables seamless control of 32 MB SDRAM, 2 MB flash-to-code storage, compact flash-to-data exchange, and an LCD display. Blackfin is available in a 400-ball miniBGA.

 Low Cost, Low Power, High Performance AED

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