Seamless Microsystems D i g i t i z i n g Yo u r W o r l d S e a m l e s s l y ADCs for Autonomous Driving Augustine Kuo VP Engineering Seamless Microsystems
Seamless Microsystems Background LiDAR and RADAR in Wireless and Consumer cars Wireline Comm. Medical Imaging SM250M SM400M SM250M SM250M 2
Silicon Valley Traffic 3
Tesla Autopilot! Available now! 4
Works most of the time, but… 5
Why Tesla’s autopilot might be failing? Tesla’s autopilot only uses cameras and radar for sensing 15 feet? 17 feet High resolution RADAR LiDAR 6
Comparison of sensors in various environments Sensor RADAR Camera/Vision LIDAR Range - Range resolution - Angular resolution - Works in bad weather Works in dark Works in bright light Radial velocity - Color/contrast 7
Most autonomous cars now use all three sensors LiDAR Camera RADAR (usually mounted behind body panels) 8
Time-of-Flight LiDAR Systems OPTICAL ANALOG DIGITAL Laser Full waveform capture LiDAR Rx 3-D Point PIN A ADC Detection Estimation Cloud APD 12Gb/s 300Mb/s Geiger/Single-Photon LiDAR Rx 3-D Point SPAD TDC Estimation Cloud array 9
Comparison of LiDAR receiver techniques LiDAR Geiger Full-Waveform Receiver Technique Mode Capture Processing simplicity/power consumption Cost Range/Resolution Quick Object Classification (reflectance data) Multi-return echo detection (ie foliage, poles/wires) Error-free from other LiDARs (interference) 10
Current LiDAR solutions use discrete chips ADC ADC ADC ADC Digital ADC ADC ADC ADC $1600 for ADCs alone (8 channels) 11
ADCs in LiDAR Are Bulky and Expensive Very hard to build ADC ADC ADC ADC Digital ADC ADC ADC ADC Large footprint Speed Resolution Power/ch. 0.9 GHz 10-bits 1W 12
LiDAR Receive Pulse Digitization Time domain Pulse + Noise LiDAR ADC Requirements ▪ Sampling speed > 0.5GHz ▪ Resolution > 10-bits 4ns LiDAR Received Frequency domain Pulse Bandwidth > 250MHz RX Chain ADC LPF 13
Problem 1: Power Hungry LPF Nyquist Alias Alias Alias Alias Alias Band Band 1 Band 2 Band 3 Band 4 Band 5 ADC 0 LPF LiDAR -5 Analog LPF Pulse -10 ▪ Significant SNR degradation due dB -15 Amplitude to noise aliasing -20 ▪ Requires expensive LPF to -25 minimize noise aliasing -30 • 8 th order LPF -35 • 4x AD8099 chips @ $14 -40 • 600mW 0 2.5 5 7.5 10 15 10 8 Frequency Hz Power hungry (600mW/ch.) and expensive ($14/ch) 14
Problem 2: Poor Jitter Tolerance ADC CLOCK LPF LiDAR Pulse ▪ Very accurate clock source requirement for ADC sampling ▪ <300fs rms jitter requirement for LiDAR ADCs ▪ Expensive • On-board clock generators: TI LMK61A2-100M00SIAT ~ $7.00 • On-chip (inside ADC) clock generators - Large Silicon area - Large cost 15
Problem 3: Power-Hungry ADC Input Driver SAR N SAR 2 RX Chain SAR 1 V REF Logic ADC LPF ▪ Switched-capacitor input interface is hard to drive • Needs power hungry buffer ▪ ADC input driver ~ 20% ADC power consumption 16
Best ADCs for LiDAR: Continuous-time DS ADCs ▪ Low-pass filtering using integrators before sampling Seamless’ Continuous -Time DS ADCs D OUT ò ò ò Calibration 4-bit SM + V IN SM - & Filtering ADC 12-bit Merged SMOA-RC Integrator-ADC 4-bit SCDAC ANALOG DIGITAL ▪ High speed sigma delta ADCs ▪ Resistive input impedance • Enabled by SMI’s patented technology • Low power ADC driver ▪ Simple digital calibration ▪ Inherent over-sampling • No requirement for anti-alias filter 17
ISO 26262 IP/Chip Requirements All IP/SoCs must meet functional safety requirements *Synopsys white paper – Data converters IP for Automotive SoCs D OUT SMSP CT + IN SD ADC - 12-bits 500MS/s SM250M F CLK = 3GHz D OUT SMSP CT + 4 channel ADC IN SD ADC 12-bits - 500MS/s SMSP CT D OUT + With 1 redundant IN SD ADC F CLK = 3GHz 12-bits - 500MS/s SMSP CT D OUT + IN SD ADC testing channel 12-bits F CLK = 3GHz - 500MS/s F CLK = 3GHz SMSP CT D OUT + IN SD ADC 12-bits - 500MS/s F CLK = 3GHz 18
IP or Chiplets? • Digital will be a large portion of the SoC DIGITAL DIGITAL • Done in lower CMOS nodes for power/cost savings • ADCs as chiplets • Does not need to be in same DIGITAL DIGITAL process as digital • Can be ISO 26262 qualified independently to reduce time-to- market ADC ADC ADC ADC ADC 19
Conclusions • For autonomous driving sensors, high bandwidth and high resolution ADCs will be needed • LiDAR/RADAR will definitely be used • Full-waveform capture needed for long range • Automotive components have long lead time • Products need to be done quickly so exhaustive tests can begin sooner • ISO 26262 compliance is easier if every component is already qualified 20
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