Download Design of Low Power and High Speed Laser Driver

Design of High-Speed Laser Driver Using
a Standard CMOS Technology for Optical
Data Transmission
Dissertation Defense Presentation
By
Seok Hun Hyun
Advisor: Martin A. Brooke
November 2004
Outline
 Introduction
 Background
 Design of A High Current Laser Driver
 Design of A Low Power Laser Driver
 Thin Film Laser Integration onto CMOS circuits
 Conclusion and Future Research
Introduction
 Objective
 Design of laser driver for optical data
transmission
 Using a standard CMOS technology
 Studying the behavior of circuit performance
with parasitic components
 Working at commercially interesting highspeed and low power consumption
Introduction
 Fundamental constraints in electronic
communication links
 Noise, Interference, Power, Cost, etc.
 Use of optics as a replacement for electronics
 LAN, MAN, board-to-board and chip-to-chip
interconnects
Background
 Optoelectronic Links
Background
 Eye Diagram
Jitter
EYE
Signal Distortion
Logic “1”
Noise
Margin
Logic “0”
Background
 CMOS technology
 Low power
 Low cost
 High yield
 Higher degree of integration
 Vast standard cell library
 TSMC 0.18 um mixed-signal CMOS
Background
 Laser Driver
 The electro-optic interface limits the maximum
speed of system
 Simple current switch responses to the input
signal modulated with data stream
 Critical challenge: To deliver large current with
very short rise and fall times since the
bandwidth is trade off for large current.
Background
 Examples of laser driver
Reference: Jerry D. Gibson, The Communications Handbook, CRC press, 1996.
High Current Laser Driver
 Required to be other types of lasers
 FP, DFB, MQW, etc.
 More than 20 mA modulation currents
 A driver for LVDS standards
 Input: 100 mVp-p
 Speed : > 10 Gbps
 Output current: Mod. 0~40 mA, Bias : 0~30 mA
High Current Laser Driver
 Hard to design a current switch with LVDS
input amplitude (100 mVp-p)
 Require pre-driver stages
 Bandwidth Enhancement Technique
 Shunt peaking
 Source degeneration
 Cherry-Hooper topology
High Current Laser Driver
 Shunt peaking
High Current Laser Driver
 Source degeneration
High Current Laser Driver
 Cherry-Hooper topology
High Current Laser Driver
 Pre-drive stage
(a) Active inductor
(b) CH topology
High Current Laser Driver
 Laser driver with CH topology
High Current Laser Driver
 Eye diagram at 10 Gbps
High Current Laser Driver
 Laser driver and simulation at 10 Gbps
High Current Laser Driver
 Eye diagram at 10 Gbps
High Current Laser Driver
 Specifications
Performance
LD with the CH
LD with active
inductors
Speed
10 Gbps
10 Gbps
Input
100mVp-p
100mVp-p
Output
Power
Mod: 40mAp-p
Bias: 30mA
694 mW
Mod: 40mAp-p
Bias: 30mA
312 mW
High Current Laser Driver
 Comparison
Speed
Mod.
Input
Power
Petersen’s work
[Ref]
10 Gbps
30 m
500 m
492.2 mW
This research
10 Gbps
40 m
100 m
312 mW
[Ref]:A. K. Petersen, K. Kiziloglu, T. Yoon, F. Williams, Jr., and M. R. Sandor, "Front-end
CMOS chipset for 10 Gb/s communication," presented at Proceedings of 2002 IEEE
Radio Frequency Integrated Circuits Symposium RFIC, 2-4 June 2002, Seattle, WA,
USA, 2002.
Low Power CMOS Laser Driver
 Parallel Optical Interconnects (POI) are
available for rack-to-rack communication at
bandwidth of up to 30 Gbps with 12 channels
of 2.5 Gbps operation
 Next generation POIs will operate at 10 Gbps
 The key to demonstrate such links is low power
laser driver and receiver
Low Power CMOS Laser Driver
 Design Goal
Specifications
Goal
Speed
Greater than 10 Gbps
Current
Bias: > 10 mA
Mod.: > 10 mA
Power
As low as possible
Current density
< 1 mA/um2
 Differential topology
 Immune to delta I noise
Low Power CMOS Laser Driver
 Simulation Process
 IC technology, Circuit topology
 Schematic-based simulations
 Verification of function of circuits
 Layout of circuit
 Parameter extraction from layout
 Re-simulations with the extracted
 Check the specifications
Low Power CMOS Laser Driver
 Schematics
VDD
VDD
For Electrical Test
Z
Z
Z1
In+
InCurrent Switch
IBIAS
Z
Z
IMOD
VSS
VSS
Low Power CMOS Laser Driver
 High speed laser model
Low Power CMOS Laser Driver
 Simulation without packaging parasitics
 Input : 800 mVp-p PRBS  Mod. : up to 10 mAp-p
 Speed : 10 Gbps
 Power : 62.5 mW
Low Power CMOS Laser Driver
 Simulation with packaging parasitics
 Wire-bonding parasitics
 Traces on test board
 Soldering and cable
Low Power CMOS Laser Driver
Current (A)
 Transient response with line parasitics
Voltage (V)
 Wirebonding : 2 nH
 Trace line : 5 nH
 Soldering, cable : 10 nH  Speed : 10 Gbps
Low Power CMOS Laser Driver
 Decoupling capacitors
Low Power CMOS Laser Driver
Current (A)
 Simulations with parasitics and decoupling
capacitors
Voltage (V)
 Input : 800 mVp-p PRBS  Mod. : up to 10 mAp-p
 Speed : 10 Gbps
 Power : 62.5 mW
Low Power CMOS Laser Driver
 Temperature Variations
Current (A)
 Yellow : 27 oC
 Red : 100 oC
 Cyan : 200 oC
Voltage (V)
Low Power CMOS Laser Driver
 Layout of Laser Driver
MiM Capacitors
ESD protection circuitry
 Multiple finger structure
 A symmetrical layout
 Current density consideration
Low Power CMOS Laser Driver
 TSMC 0.18um Chip Layout
Transimpedance
amplifier
Laser Drivers
Calibration
transistors
Low Power CMOS Laser Driver
 ESD protection circuitry
 Positive ESD Pulse are
clamped to the
ESD_VDD
 Negative ESD pulse
are clamped to the
ESD_VSS
Low Power CMOS Laser Driver
 Test Setup
Low Power CMOS Laser Driver
 Test board
5 GHz
S(21) dB
-2 dB
-5 dB
Frequency (Hz)
 Transmission characteristics (S21) of the traces
on the test board using HPADS
10 GHz
Low Power CMOS Laser Driver
 Transient response test
@ 1 Gbps
 Error-Free Operation
@ 5 Gbps
Low Power CMOS Laser Driver
 Transient response test
@ 10 Gbps
 3.11 x 10
-14
@ 12 Gbps
BER at 10 Gbps
Low Power CMOS Laser Driver
 SONET OC-192 eye mask
Low Power CMOS Laser Driver
 Simulation vs. Measurement
 Simulation
 Measurement
Low Power CMOS Laser Driver
 Optimized specifications of the laser driver
Specifications
Conditions
Laser modulation
up to 12 mA
Power Dissipation
65.5W
Speed
over 10 Gbps
BER
> 3.11 X 10-14
Area
825 X 613 μm
Technology
TSMC 0.18 μm CMOS
Low Power CMOS Laser Driver
 Published laser drivers
Authors
Speed
Modulation
Bias
Input
Chan G.C
2.5 Gbps
20 mAp-p
Chan C.T
2.5 Gbps
20 mAp-p
Petersen A. K
10 Gbps
30 mAp-p
Cao, J
10 Gbps
8 mAp-p
N/A
LVDS
0.18 um
CMOS
Eo, J.Y
10 Gbps
N/A
N/A
250 mVp-p
InGaP HBT
Alexandru A.C
10 Gbps
20 mAp-p
10 mA 800 mVp-p
N/A
N/A
40 mA 500 mVp-p
10 mA 400 mVp-p
Technology
0.35 um
0.18 um
CMOS
0.18 um
CMOS
SiGe HBT
Low Power CMOS Laser Driver
 A detailed comparison
 Low power consumption
 Up to 12 Gbps operation
 The lowest input voltage
Speed
Mod.
Input
Power
Eo’s work
10 Gbps
N/A
250 mV
65 mW
Petersen’s work
10 Gbps
30 m
500 mV 492.2 mW
This research
12 Gbps
10 m
800 mV
65.5 mW
This research
10 Gbps
40 m
100 mV
312 mW
Thin Film Laser Integration onto
CMOS Circuits
 Edge emitting laser
20 mA
0 mA
 developed by GT
optoelectric group
Thin Film Laser Integration onto
CMOS Circuits
 Thin film integration
 Separate fabrication
 Independent optimization
 Reduce packaging parasitics
Thin Film Laser Integration onto
CMOS Circuits
S(21) dB
S(21) dB
 Metal line experiments
 500 um length and 20 um spacing b/w lines
 3 um SiO2 on a silicon substrate
Thin Film Laser Integration onto
CMOS Circuits
 A photograph of the fabricated optical
transmitter
Thin film Laser integration onto
CMOS chip
 Simulation and Measurement
 Simulation
 L-I measurement
Conclusion and Future Work
 High-speed and low power CMOS laser driver
was designed and tested
 High-speed laser diode and parasitics in
packaging were modeled and incorporated in
the driver design
 Low power consumption at 10 Gbps speed
 The driver compatible with LVDS IEEE standard
was designed, simulated
 The first demonstration of thin film laser onto
CMOS laser driver
Conclusion and Future Work
 Future Work
 Speed verification of the optical transmitter with
a thin film laser
 Additional function blocks such as a multiplexer
 Verification of high-current LVDS driver circuitry
 Implementation of optical transceiver with
optical receivers.
Questions