1. High Speed Analog Serialization EECS 713 Michael Blecha

2. Outline  Applications  Analog to Digital Converters (ADCs)  Low Voltage Differential Signaling (LVDS)  Project Deliverables 2

3. Application Examples  Oscilloscope Front End  Modern oscilloscopes have digital front ends  Analog information is digitized and sent to processing/display module  Radio Front End  RF signal is mixed down to baseband and digitized  Most modern radios use digital demodulation  Sensor networks  “Real world” information is analog  Most control loops and decision making processes occur in the digital domain 3

4. ADCs  Characteristics  Resolution: low (8 bit) to high (16 bit,24 bit +)  Sampling rate: 10s of kSPS to 100s of MSPS  Bandwidth: frequency range that can be sampled  Signal to noise ratio: Ratio of signal to noise introduced  Channels: number of simultaneous parallel data acquisitions  Resolution vs. sampling rate tradeoff  DSPS have finite processing power  Interface has finite bandwidth  DSP may be optimized for certain word sizes (8, 16, 24 bit) 4

5. ADC PCB Guidelines  Standard high speed digital design practices remain critical  Ground split  Often helpful, sometimes detrimental if done incorrectly  Star ground often used, connecting analog and digital grounds at single point  Analog and digital portions of ADCs often have different ground return paths (usually different ground pins/balls/pads)  Goal is to have digital return path far from analog section  Power split  Use separate supplies for analog and digital portions  Split power plane and connect with inductors or ferrite beads 5

6. LVDS  Serial data transmission interface  Point-point interconnections most common, but multi point fly-by topologies are possible  Low voltage: about 350mV peak to peak  Differential: differential signals terminated with 100 Ω load  Low susceptibility to noise because common mode noise is ignored  Low radiated emissions because opposite currents cancel magnetic fields  Low power consumption 6

7. LVDS Use Cases 7  PCB interconnect  Can connect components 10s of centimeters apart  Some I.C.s have built in terminations, others require external 100 Ω differential termination  Generally implemented as a pair of closely coupled 50 Ω single ended striplines or microstrips  Twisted pair  Up to meters in length  Higher speeds need more tightly specified cables (similar to Cat5 vs. Ca6 Ethernet cables)  Commonly used by video display standards (ex: FPD-Link)

8. LVDS Standards  Standardized by ANSI 644  Up to 1.9GBit/sec  Z o = 90 Ω - 132 Ω  1.2V common mode  250mV-450mV transmitted differential voltage  100mV differential sensitivity at receivers 8

9. Project Deliverables  Background information  ADCs  LVDS  High resolution serializer design  16 bit ADC at 50-100MSPS  LVDS serializer to export data to external DSP  Using separate ADC and serializer to perform timing analysis and determine timing interdependencies of ADC, LVDS driver, and clocking 9

10. References  http://www.ti.com/lit/an/slla038b/slla038b.pdf http://www.ti.com/lit/an/slla038b/slla038b.pdf  http://www.analog.com/static/imported- files/application_notes/5957542118600205599850975382 134073431740717454123180480718AN586.pdf http://www.analog.com/static/imported- files/application_notes/5957542118600205599850975382 134073431740717454123180480718AN586.pdf  http://www.analog.com/static/imported- files/application_notes/AN-1142.pdf http://www.analog.com/static/imported- files/application_notes/AN-1142.pdf  http://www.analog.com/static/imported- files/application_notes/AN-1177.pdf http://www.analog.com/static/imported- files/application_notes/AN-1177.pdf 10