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Medical buyers deMandMixed signal solutions
Equipment in themedical field increasingly requires high performance, small size and low power: enter the latest analogue and digital ICs fromLinear Technology
Fromhigh resolution imaging systems to drug delivery systems and implantable electronics, Linear Technology’s portfolio caters for a variety ofmedical applications.
Monitoring such as ECG/EEG and pulse oximetry, aswell as blood
and fluid analysis require precision analogue-to-digital conversion with sample rates up to 1Msps. Depending on the system architecture, 12 to 16-bit SAR type ADCs are good choices.
Linear Technology’s ADC designs achieve newSNR performance
with the LTC2379-18, 18-bit 250ksps to 1.6Msps SAR ADC family. The device automatically powers down between conversions,while reducing power dissipation as the sampling frequency decreases. Its no-latency operation is said to enable accurate one-shot measurements even after lengthy idle periodswith nominimum sample rate required.
Home health
Portable self-care systems can be used tomonitor vital signs such as blood pressure, blood sugar and temperature. Some measurements require analogue circuitry to run continuously, while other applications require a single reading per day. For occasional tests, the analogue circuitrymust only power up once, take themeasurement and then sit idle, running on a low power 'sleep'mode the rest of the day. Linear's LTC2470 family of 16-bit 1ksps delta-sigma ADCs with internal references and a choice of SPI or I2C interfaces are perfect for these portable applications.
Medical imaging
Medical imaging applications use a range of high performance data converters. Ultrasound, PET/SPECT,magnetic resonance imaging (MRI) and x-ray imaging all usemultichannel sampling systems to gather image data. Since these applications require awide dynamic range, the performance of the ADC is critical. High SNR and spurious free dynamic range (SFDR) are needed for optimal performance. Additionally, in applications such asMRI,where undersampling techniques are used, wide bandwidth sample and hold performance is critical.
Tomeet these demands, Linear Technology has a newline of
25Msps to 125Mspsmultichannel ADCs for imaging applications: the dual 16-bit LTC2195, 14-bit and 12-bit quad LTC2175 and dual LTC2268 ADCswith serial LVDS outputs consume a little over 1mW/Msps per channel.
High reliability imaging systems also require complex digital power
management to sequence, supervise,monitor andmargin a number of voltage rails. Typically these solutions require several discrete devices controlled by an FPGA or microcontroller,with significant time and effort required to develop the necessary firmware.
Alternatively, the LTC2978 octal digital power supplymanagerwith
EEPROMoffers an integrated,modular solution said to reduce debugging time and effort. It can sequence on, sequence off, monitor, supervise,margin and trimup to eight power supplies.
www.linear.com
Linear Technology's productmarketingmanager formixed signal products, Alison Steer, discusses emergingmedical applications
52 |March 2011
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