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] 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 2] 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 3] 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 4] Cochlea Neuro stimulation Defibrillator Cardiac pacemaker Heart Sensor Drug delivery/ Insulin pump Bladder control devices MICS - Applications Clinical Setting - Consultations and Operating room RF Link Cardiologist with Programmer Patient with Pacemaker / ICD Home Monitoring [Page 5] Transfer to Hospital Challenges Low Power Consumption - Low TX/RX current <6mA, battery considerations - Low sleep/listen current, ideally <100s of nA Minimum External Components - Implantable RF module <5x5x12 mm Module size 2 x 5 x 12 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 and body loss typically 40 dB Reliability - Data and link integrity, selectivity and interference rejection [Page 6] Design Solutions Key Concept - Duty Cycle - Duty cycle normal data exchange for given data rate - Duty cycle sniffing for wakeup - 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 7] ULP Implantable Transceiver (ZL70100) 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: < 200 nA Ext. comps: 2 (excluding antenna matching) BER: <1.5 x 10-10 Range: ~2 m [Page 8] ZL70100 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 – 2 pieces plus antenna matching [Page 9] – 5 mA continuous TX/RX – <1mA low power TX/RX Ultra Low Power Wake-up Circuit – <200 nA Multiple Startup Methods – 2.45 GHz signal – Pin Control (for Emergency messages, 400 MHz sniffing, low frequency inductive link sniffing or other wakeup methods) Standards Compatible – MICS, FCC, IEC ZL70100 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 10] ZL70100 Block Diagram XTAL2 Zarlink MICS Transceiver - ZL70100 XTAL1 24 MHz 400 MHz Transceiver Media Access Controller PLL ADCanalog Inputs 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 3 Analog Inputs 4 Peak Detector Antenna Matching Mixer RX rx_data ADC RX RX Control Correlator RX IF Filter and FM Detector 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 VSUP Enable Battery or Other Supply [Page 11] CRC Decode Input Pin Pull-down Control Wake-Up Control RX Antenna Matching Ultra Low Power Oscillator VSSA RX 2.45 GHz Interf ace SPI Control VDDIO RF 400 MHz DataBus RSSI Low Noise Amplif ier RX 400 MHz 5bit ADC Programmable PO[3:0] IO PI[2:0] SPI_CS_B SPI SPI_CLK Interface SPI_SDI SPI_SDO IRQ 2 MODE[1:0] PDCTRL XO_BYPASS IBS WU_EN ZL70100 Typical 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 VSUP VDDIO RX_245A SPI_SDI RX_245B SPI_SDO VSSA_WAKE_LNA SPI_CLK VSSA_GEN1 VSSD ZL70100 RF_TX Matching network dependent on antenna VSSA_RF_PA VDDD PDCTRL* (3 x 4 mm2) RF_RX VSSD VSSA_RF_LNA SPI_CS_B TESTIO4 TESTIO3 TESTIO2 TESTIO1 XTAL2 IRQ XTAL1 VSSA_RF_XO VSSA_GEN4 VSSA_GEN3 CLF_REF CLF2 CLF1 WU_EN 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 12] Application Interface RF Module Technology for Implants Ceramic, FR4, Rigid Flex I/O Connectivity Flex [Page 13] 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 14] The Diagnostic Procedure (Company: Given Imaging) Healthy Small Bowel [Page 15] The Camera Pill Size: 11 x 26 mm Weight: < 4 gram View: 140 deg Approximately 57,000 pictures during 8 hours [Page 16] The Camera Pill World’s Only Swallowable Camera Capsule, from Given Imaging, including Zarlink’s ULP RF Transmitter Size: 11 x 26 mm, Weight: < 4 gram, View: 140 deg Approximately 57,000 pictures during 8 hours Zarlink’s RF chip A Real ”Fantastic Voyage” [Page 17] 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 18] Summary RF integrated circuits for the MICS and ISM bands will open up a new range of clinical applications for the next generation medical devices. The development of such circuits requires cutting edge technology and design with specific attention to power consumption Chips for implantable medical products and complete RF modules solutions are available now ! [Page 19] SIMPLY COMMUNICATING