RF Integrated Circuits for Medical Implants: Meeting the Challenge of Ultra Low-Power Communication Peter Bradley, Ph.D. System Engineering Manager, Ultra Low-Power Communications Division, Zarlink Semiconductor, (Email: [email protected]) Outline – The MICS Band – Applications for Medical Devices – Ultra Low-Power (ULP) Design Challenges – Design Solutions – Design Examples ZL70100: The Implantable Transceiver ZL70081: The Swallowable Camera Pill Transmitter ZL70262: ULP Audio Transmitter (Hearing Aids) – Conclusion [Page 1] History – Implanted Medical Telemetry 1980s – Inductive Telemetry – – – – Near field (sub 1 MHz) at data rates <50 kHz Low power (<1 mA) Pick up in implant using small coil Very short range (10 cm max) requiring close skin contact Inductive Wand IMD ~10 cm max range 1999 – RF Telemetry – – – – – – – Medical Implant Communication Service (MICS) Band 402-405 MHz frequency allocation FCC was petitioned in mid–1990s, spectrum allocated in 1999 2003 Biotronik release MICS device (non-compliant) 2004 Medtronic release MICS device 2005 Guidant release ISM band (915 MHz) device ISM bands (13.56, 433, 868, 915 MHz) are sometimes used 2002 - Ultrasonic Telemetry [Page 2] Programmer The MICS Band Medical Implant Communication Service (MICS) – 402-405 MHz frequency allocation FCC was petitioned in mid-1990s, allocated in 1999 – Short-range, wireless link to connect low-power implanted medical devices with monitoring and control equipment Implanted Medical Devices (IMD) such as cardiac pacemakers, implantable cardioverter defibrillator (ICD), neurostimulators, etc. – Why introduce MICS ? - Removes limitations associated with existing short range inductive links (low data rate, very short range requires body contact) - Opportunity for improved healthcare and new applications – Why 402-405 MHz? - Reasonable signal propagation characteristics in the human body - Compatibility with incumbent users of the band (e.g. weather balloons) - General world-wide acceptance (US, Europe, Japan, Australia etc) [Page 3] Why was MICS Introduced? Need for higher data rates – To upload patient events captured in the IMD’s memory to the base station for analysis – Shorten doctor/patient consultancy times Need for longer range – Simplify home-monitoring for elderly – Locate the base station (programmer) outside of the sterile field during surgery – Broaden possible applications: Bedside monitor for emergency Competitive pressure of medical device industry – Higher data rates enable new, value-added services [Page 4] MICS Applications Deep brain stimulation Stimulatory Devices – Pacemaker – Implantable Cardioverter/Defibrillator (ICD) – Neurostimulators and pain suppression devices – Cochlea implants/hearing aids Measurement/Control/Other Devices – Drug infusion and dispensing – Artificial heart and heart assist devices – Implanted sensors – Control of other artificial organs and implanted devices [Page 5] Cochlea Neuro stimulation Defibrillator Cardiac pacemaker Heart Sensor Drug delivery/ Insulin pump Bladder control devices MICS Benefits – Operating Room Today [Page 6] Future with MICS CONFIDENTIAL MICS Benefits – Home Monitoring Today [Page 7] Future with MICS CONFIDENTIAL MICS Benefits – Doctor’s Office Today [Page 8] Future with MICS CONFIDENTIAL Potential Driver: Reliability Monitoring Recall Medical device failures exceptionally costly – Example 1: Recent Guidant battery issues Recall and 15% sales drop – Example 2: St Jude cosmic radiation memory problem 60 reported failures out of 36000 devices Remote monitoring could substantially reduce patient impact and cost Extract from Physician Letter: Oct-6th-2005, St Jude http://www.sjm.com/ companyinformation/physicianletter.html [Page 9] Challenges Low Power Consumption - Low TX/RX current <6mA, battery considerations - Low sleep/listen current, ideally <100s of nA Minimum External Components - RF module <3x5x10 mm Module size 3 x 5 x 10 mm - Fewer components => higher reliability, lower cost, smaller size Reasonable data rates - Pacemaker applications >20 kbps and higher projected in the future Operating range - Require ~2 m to improve on existing links (short range inductive) - Antenna matching, fading and body loss typically 40-45 dB Reliability - Data and link integrity, selectivity and interference rejection [Page 10] Design Solutions Key Concept – Duty Cycle - Duty cycle normal data exchange for given data rate - Duty cycle sniffing for wake-up - Turn off sub-systems in chip when not required Use the highest possible data rate for required sensitivity - Apply concept even for systems that require low data rates (low kHz range) - Sending data in short bursts conserves power - Reduces time window for interference and easier supply decoupling High Data Integrity - Reed-Solomon Forward Error Correction, CRC error detection - Capable of several years continuous operation without error High Level of Integration - Sub-micron CMOS RF technology [Page 11] ULP Implantable Transceiver (ZL70101) MICS and ISM Band Transceiver: • Negligible standby current • high data and low error rates in a small footprint Technology: 0.18 um RF CMOS Supply Voltage: 2.1 - 3.5 V Battery Radio Frequency: 402-405 MHz (MICS-Band) Type of RF link Bi-directional, half duplex Modulation Scheme: FSK Raw Bit Rate: 800 / 400 / 200 kbits/s Operating Current: 5mA TX/RX down to <1mA Sleep Current: < 250 nA Ext. comps: 3 (excluding antenna matching) BER: <1.5 x 10-10 Range: ~2 m [Page 12] ZL70101 Key Features 12 Channels Extremely Low Power – 402-405 MHz (10 MICS) – 433-434 MHz (2 ISM) Selectable Data Rate – 200/400/800 kbps raw data rate High Performance Media Access Controller (MAC) – Auto error handling and flow control, Reed-Solomon, CRC – Typically <1.5 x10-10 BER Min. External Components – 3 pieces plus antenna matching [Page 13] – 5 mA continuous TX/RX – <1mA low power TX/RX Ultra Low-Power Wake-up Circuit – <250 nA Multiple Start-up Methods – 2.45 GHz signal – Pin Control (for Emergency messages, 400 MHz sniffing, low frequency inductive link sniffing or other wake-up methods) Standards Compatible – MICS, FCC, IEC ZL70101 MICS System Base Station Wake-up link Implanted Medical Device (IMD) RF data link 402-405 MHz 2m operating range* * Dependent on antenna performance [Page 14] Wake-Up Receiver Problem: MICS band limited to 25 uW (-16 dBm) Solution: Use band with more power 2.45 GHz (up to 20 dBm) and design synthesizer-less receiver – High Gain LNA and OOK detector – Manchester coding of pulses – 250 nA average current for 1.15 second latency Possible to use for other sniffing/wake-up applications WU_EN [Page 15] ZL70100 Block Diagram XTAL2 Zarlink MICS Transceiver - ZL70100 XTAL1 24 MHz 400 MHz Transceiver ADCanalog Inputs Media Access Controller PLL 4 To ADC Mux RS Encoder Whitening Power Amplif ier CRC Generation Message Storage Mixer tx_data TX 400 MHz RF 400 MHz TX TX IF Modulator + TX Control tx_clk 4 Analog Inputs 4 Peak Detector Antenna Matching RX 400 MHz RF 400 MHz 5bit ADC Mixer RX rx_data ADC RX RX Control RS Decode Clock Recov ery 2.45 GHz Wake-Up Receiver RF 2.45 GHz Message Storage Test Mode Control By pass of on-chip Cry stal Oscillator Control Regulator 1.85 -2.0V Select IMD or Base Transceiv er Wakeup IMD 68 nF Decoupling Capacitor VSSD VDDD VDDA VSSA Enable Battery or Other Supply [Page 16] CRC Decode Input Pin Pull-down Control VSUP Antenna Matching Ultra Low Power Oscillator Wake-Up Control RX Programmable PO[3:0] IO PI[2:0] SPI_CS_B SPI SPI_CLK Interface SPI_SDI SPI_SDO IRQ Correlator RX IF Filter and FM Detector RX 2.45 GHz Interf ace SPI Control DataBus RSSI VDDIO Low Noise Amplif ier 3 2 MODE[1:0] PDCTRL XO_BYPASS IBS WU_EN ZL70101 Block Diagram MICS Transceiver XTAL1 XTAL2 Improvement on ZL70100 (matching and power regulation) Media Access Controller 400 MHz Transceiver ADC analog Inputs (TESTIO [4:1] pins) 4 To ADC Mux PLL Power Amplifier RF_TX RF 400 MHz Whitening Mixer CRC Generation RS Encoder tx_data TX TX IF Modulator + tx_clk TX Control Peak Detectors 5 Analog Inputs 4 MATCH1 MATCH2 5bit ADC 3 DataBus RSSI Control Interface SPI Matching nework Linear Amplifier RF_RX RF 400 MHz Mixer RX ADC RX RX Control rx_data RS Decode Clock Recovery 2.45 GHz Wake-Up Receiver Regulator 1.85 - 2.0V ULPOsc RF 2.45 GHz RX IRQ CRC Decode Message Storage Test Mode Control Input Pin Pull-down Control Bypass of on-chip Crystal Oscillator Control Regulator 1.85 - 2.0V Wake-Up Control Select IMD or Base Transceiver Wakeup IMD Select one or two regulators [Page 17] 68nF 68nF VDDIO VSSD Decoupling Capacitors VDDD VDDA VSUP VSSA Analog Test TESTIO[6:5] 2 Battery or Other Supply Programmable IO PO[4:0] PI[2:0] SPI_CS_B SPI_CLK SPI SPI_SDI Interface SPI_SDO Correlator RX IF Filter and FM Detector RX_245 Message Storage 2 MODE[1:0] PDCTRL XO_BYPASS IBS WU_EN VREG_MODE ZL70100 Example Implant Design VDDA2 To VSUP (main supply) MODE1* MODE0* PI2* PI1* PI0* VSSD PO3 PO2 PO1 PO0 XO_BYPASS Optional DC-blocking capacitor IBS* VDDA1 VDD (internal regulator) VSSD VDDIO VSUP RX_245A SPI_SDI RX_245B SPI_SDO SPI_CLK VSSA_WAKE_LNA VSSA_GEN1 ZL70100 RF_TX Matching network dependent on antenna VSSD VSSA_RF_PA VDDD PDCTRL* (3 x 4 mm2) RF_RX VSSD SPI_CS_B VSSA_RF_LNA WU_EN TESTIO4 TESTIO3 TESTIO2 TESTIO1 XTAL2 IRQ XTAL1 VSSA_RF_XO VSSA_GEN4 VSSA_GEN3 CLF_REF CLF2 CLF1 TESTIO[6] TESTIO[5] VSSA_RF_VCO VSSA_GEN2 RBIAS To VDD Note 1: *Inputs connected via internal pull-down to ground. Right-hand side pins do not need to be bonded out Note 2: Two supply voltages are required VSUP (the main supply,2.1-3.6V) and VDDIO (the digital IO voltage which may be 1.5V to VSUP) VDD is an on-chip derived regulated supply which requires a 68 nF decoupling capacitor and connection of VDDA to VDDD [Page 18] Application Interface RF Module Technology for Implants Ceramic, FR4, Rigid Flex I/O Connectivity Flex [Page 19] WireBond / Solder LGA / BGA ULP Medical Transmitter (ZL70081) Very high data rate transmitter low power small footprint designed for imaging applications Technology: 0.35µm CMOS Supply Voltage 2.6 - 3.2 V Battery Radio Frequency: 400 - 440 MHz Type of RF link: Transmit only Bit Rate: 2700 kbits/s Operating Power: 5.2 mW Ext. comps: 10 [Page 20] The Diagnostic Procedure (Company: Given Imaging) Healthy Small Bowel [Page 21] The Camera Pill (1) Size: 11 x 26 mm Weight: < 4 gram View: 140 deg Approximately 57,000 pictures during 8 hours [Page 22] The Camera Pill (2) World’s only Swallowable Camera Capsule, from Given Imaging, including Zarlink’s ULP RF Transmitter [Page 23] CONFIDENTIAL ULP Audio Transceiver (ZL70262) Hearing Aid wireless link: • Device programming • Ear to ear volume control • Ear to ear communication for active noise cancellation and directional hearing Technology: 0.18 µm RF CMOS Radio Frequency: 915 MHz (Americas) / 863-865 MHz (Europe) Type of RF link: Bi-directional, half duplex Bit Rate: 186 kbits/s Current Consumption: <2 mA from 1.05 - 1.5 V Battery (cf ~90 mA Bluetooth) Range: 4 meters Externals: 2 (Xtal,Res) [Page 24] Summary RF integrated circuits for the MICS and ISM bands will open up a new range of clinical applications for next-generation medical devices. The development of such circuits requires leading-edge technology and design with specific attention to power consumption Integrated circuits, modules are available now and are being used in the latest medical devices development [Page 25] Opportunities for Research and Development Further characterization of RF propagation in and around the body is required, fading effects, interferer analysis in various countries Electrically small antennas for the body environment Ultra Low-Power architectures Ultra Low-Power coding schemes Development of MEDS band – MEdical Data Service – Regulatory approval and definition still in progress – 401-402 and 405-406 MHz, 100 kHz channels – For external medical applications (eg blood oximeters, ECG) Currently servicing existing applications but… miniaturized radios and associated power systems can open up new applications [Page 26] Zarlink Semiconductor