1. Wireless data and power Brian McKinney Michael Vincent

2. What we are doing • Ultimate goal is to create a device capable of precisely stimulating tissue in-vivo without connection to outside • Lack of external connection implies IC needs to derive both power and data from RF signal

3. Transmitter • Not a mixed signal IC but needed for simulation and testing purposes • Generates random data • Frames random data (e.g. start/stop and parity bits) • Modulates carrier (ASK) with framed data

4. Example

5. Rectifier • Converts AC to DC • analog begin V(vout) <+ abs(vin); end

6. Regulator • “Buck” type step down switching regulator

7. Functional Design RampGenerator – Makes ramp signal with specified period and amplitude Regulator – Pulse Width Modulator, compares output voltage with ramp, adjusts duty cycle of square wave to produce desired output voltage

8. Specs (theoretical) • Designed to source 25 mW at 3.3V • Switching frequency: 100 kHz • Inductor and capacitor values: • Make square wave coming from switch look DC • While supplying sufficient current to load during both phases (charge and discharge) • In our case, L = 1 uH and C = 10 uF (used switching frequency as a start and then a lot of trial and error) • Corner frequency ~ 50 kHz • Ripple current ~ 112.1 uA => 10.1% ripple

9. So far…

10. Data Path Envelope Detector Input: AM Signal (4MHz) Output: 100 Kbps “Dirty Data” Clock Recovery Input: 100 Kbps “Dirty Data” Output: 100 KHz Synchronous Clock Timing Control Inputs: 100 Kbps “Dirty Data” 100 KHz Clock Outputs: Clean Clock, Clean Data, Frame Strobe

11. Envelope Detector

12. Envelope Detector Simulation

13. Clock Recovery

14. Clock Recovery (Cont.)

15. Timing Control • dirtyData shifted into register on rising edges of dirtyClk • Search for start frame • Two start bits • Eight zero data bits • Valid Parity and Stop bits • Enable Output and start sync counter

16. Timing Control (Cont.) • Strobe signal indicates valid frame data is about to start • Valid clock and data (with frame info) shifted out • Invalid bytes will result in “dead time” on output clock, data and strobe lines

17. Timing Results

18. Conclusions and Q&A