April Features: Switching power amplifier (AP) Power link and bidirectional. Demodulator. Modulator. User Interface

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1 April 2011 Introduction Power and data links Inductive link Choice of carrier frequency Transmitted power limits Inductive system modeling Conditioning and calibration techniques iscrete and integrated circuitries Power transfer Up and downlinks data transmission Modulation and demodulation atteries Miniature, rechargeable, etc. GM ispositifs Médicaux Intelligents 2 Features: Switching power amplifier (AP) Modulator emodulator Power link and bidirectional User Interface Local frequency generator Power source Processing - Power supply management - PA calibration - Inductive link coupling factor and resonance frequency calibration - Extensive data processing data Transfer by external inductor (antenna) GM ispositifs Médicaux Intelligents 3 1

2 Off chip inductor Rectifier LO Reg 1 Load Shift Key (LSK) Shunt regulator Encoder Switched Capacitor C/C AC LO Reg 2 LO Reg n M U X Analog Front- Ends (1..n) V1 V2 Vn Tissues contacts Start-up Circuit ASK/PSK emodulator Controller/ Stimulator Protection Circuit Clock Generator Circuit GM ispositifs Médicaux Intelligents 4 GM ispositifs Médicaux Intelligents 5 In most high-precision cases, even the voltage ripple after lowpass filtering is not acceptable Use a voltage regulator ~15 ua for the reference current; ~70 ua to break down the zener diodes. GM ispositifs Médicaux Intelligents 6 2

3 SET SET SET ata downlink ifferent applications ifferent data rates. GM ispositifs Médicaux Intelligents 7 ASK emodulator Vcc Manchester ecoder MANCH_IN G_CLOCK R C ATA_IN GM ispositifs Médicaux Intelligents 8 High > est efficiency, but Envelop transition time is limited by -factor of receiver Manchester encoding data rate is ~ MHz. Enhance ata Rate & Power Transfer by reducing carrier OFF period. igital decoder based on carrier signal attenuation Coil igitized direct in R1 R2 elay A Majority Env. R2 igitized attenuated in Attenuation Envelop etection Glitch Suppress GM ispositifs Médicaux Intelligents 9 3

4 Coil R1 R2 R2 elay A Majority Env. Toggling of attenuated carrier detected by toggling of direct carrier. Vdd + Vi irect coil VthH Att. coil VthL Vss - Vi ig. dir. in ig. att. in Aout out Env GM ispositifs Médicaux Intelligents 10 Walkins -Johnson Company Tech-nodes, Vol.7, No.5, GM ispositifs Médicaux Intelligents 11 ata transmission PSK emodulator (COSTAS Loop) Gilbert multiplier ata In m(t) sin(w1t+o1) m(t) = 1 or 1 2 sin(w1t+o2) VCO Arm LP Filter Low Pass Filter I branch ata out Phase Gilbert Shifter 90 multiplier 2 cos (w1t+o2) Arm LP Filter branch Gilbert multiplier Recover carrier/ data in the same loop GM ispositifs Médicaux Intelligents 12 4

5 V m VN VP VN Implementation of Costas loop circuit Gilbert Multiplier Arm Filter I branch out ata in Receiver Coil uadrature Signal Generator Voltage Controlled Oscillator (VCO) Loop Filter Gilbert Multiplier Gilbert Multiplier Arm Filter branch Requirements: 1) Fully integrated 2) Low power consumption 3) Fully differential GM ispositifs Médicaux Intelligents 13 Arm Filter I branch ata in Clk out uadrature signal generator VCO Loop Filter Chopper multiplier Receiver coil igital domain Arm Filter Analog domain branch GM ispositifs Médicaux Intelligents 14 ifferential exclusive OR Chopper multiplier VN A Z VIP VP VOP A Z VIN VON Verr 0 Output voltage versus phase error GM ispositifs Médicaux Intelligents 15 5

6 M16 M15 M18 M14 M13 M17 M10 M9 M1 M7 M3 M4 M8 M12 M2 M20 M19 M23 M22 M21 M24 SET SET V PSK input CP Von M5 M6 M11 Vop Received carrier Vinn Vinp CN Hard-limited carrier N VSS Fully differential comparator Simulation result of the comparator GM ispositifs Médicaux Intelligents 16 The voltage controlled oscillator (VCO) V M11 M12 P CP M13 M14 MP11 MP12 M3 M4 Voutp uadrature signal generator R1 Voutn Vinp Ic M1 M2 OUT M9 M10 i ctrl Vtune OUT Vinn M15 CN M17 MN14 M5 C1 M6 IN OUT M16 M18 MN13 M7 M8 IN OUT Gm Cell VSS Relaxation Oscillator GM ispositifs Médicaux Intelligents 17 ASK demodulators [LIU2000] [AKI1998] Monolithic implementation ata rate (kbps) Power consumption < 250 N/A < mw Simulation & Experimental results Parameters Transmitter Coil (PC) Receiver Coil (PC) Coefficient Tech CMOS Circuit area Carrier Freq. Supply Volt. VCO gain ata rate Power Cons. Simulated Measured 1.25 H 5 turns, = 3.5 cm 1.25 H 5 turns, = 2.7 cm 0.07 istance !m 0.18!m NA 0.19 mm MHz 10 MHz 1.8 V 1.8V/3.3V 14.7 M 13.5 M rad/s 1.51 Mbps 1.12Mbps 652 W 610 W ER NA 1.00E-04 GM ispositifs Médicaux Intelligents 18 6

7 Input Signal Vs(t) Sin(w1t+q2) VCO 90 - Phase Shifter Cos(w1t+q2) ata Out A Vd(t) - + ata Out I branch ata out Input Signal VCO Phase Shifter 90 branch ~10 Mbps < 1 mw GM ispositifs Médicaux Intelligents 19 Low-power transceiver GM ispositifs Médicaux Intelligents 20 Functional tests (electrical, mechanical,..) Circuits, Package, Heat, Reliability, Toxicity,. Self-test and fault detection after implantation Noise considerations and grounding (multichannel aspect) Analog/digital blocks, Scan and IST, overhead resources power/area In vivo measurement and validation Humidity, temperature, Ion concentration, ph, interface to tissues, Experiments in animals and humans: spontaneous or evoked activity Ethics, experimental protocol and approvals. GM ispositifs Médicaux Intelligents 21 7

8 RL RF Inductive Powering : attery Nominal Voltage = 1.55V GM ispositifs Médicaux Intelligents 22 RF Inductive Powering : attery GM ispositifs Médicaux Intelligents 23 RF Inductive Powering : attery Power Supply 5V Regulator ~3.7V C/C Up Converter 3.3V Control Unit Enable Recharge + - ischarge FPGA GN Voltage (V) 3 37ºC 200uA Load Rechargeable attery: 3V, 100mAh 1000 Cycles of 10% discharge 1 0 uration (h) GM ispositifs Médicaux Intelligents 24 8