Laser Driver handles medium reach optical communications.

Press Release Summary:

Suited for Vertical Cavity Surface Emitting Laser Diodes, 3.2 Gbps Model LTC5100 maintains very low noise transmission eye diagrams. Digital controller with on-chip A/D and D/A converters provides continuous closed-loop monitoring and control of critical laser parameters. Driver can be operated in standalone mode or controlled by external microprocessor via built-in I2C(TM) Serial Interface port. Automatic Power Control mode and Constant Current Control mode are user-selectable.

Original Press Release:

A Highly Integrated 3.2Gbps Laser Driver for Vertical Cavity Surface Emitting Laser Diodes

MILPITAS, CA - January 6, 2004 - Linear Technology Corporation introduces a highly integrated 3.2Gbps VCSEL (Vertical Cavity Surface Emitting Laser) diode driver for short reach and medium reach optical communications. The LTC5100 maintains a clean, very low noise transmission eye diagram. It incorporates a feature-rich digital controller with on-chip A/D and D/A converters to provide continuous closed-loop monitoring and control of critical laser parameters. The LTC5100 is targeted for Gigabit Ethernet and Fibre Channel optical links, multi-rate medium (under-20km) and short range fiber optic datalinks, short reach SONET links, and short-haul backplane-interconnect systems.

The LTC5100's digital controller offers unprecedented programmability and range to accommodate a wide variation of VCSEL laser operating characteristics. The user can set the desired laser bias current, modulation current, laser power, peaking characteristics, and first- and second-order temperature coefficients of a particular laser diode, while storing the setup data in a small and inexpensive external EEPROM. Using a digital feedback loop that monitors the on-chip temperature sensor, the LTC5100's on-board controller drives the laser to the desired optical power levels while compensating for any temperature drift of the laser parameters. The user can select one of two operating modes, Automatic Power Control or Constant Current Control. This closed-loop control removes diode variations, resulting in better manufacturability and consistent quality in the end-product. Moreover, the digital programmability of the laser drive system facilitates automated production setup instead of costly manual adjustments.

The LTC5100 produces consistent and low jitter eye diagrams. Unlike prior laser drivers, the LTC5100 output eye shows minimal variation with temperature, or with laser bias or modulation current level. The precisely controlled true 50Ù output termination minimizes the problem of reflection-induced distortion of the eye diagram, while allowing placement of the laser diode at an arbitrary distance from the driver output with minimal effect. The LTC5100's grounded cathode output topology significantly reduces EMI (Electro Magnetic Interference) emission. On the input side, the LTC5100's differential port is AC coupled and is 50Ù terminated, so that no external components are required. The LTC5100 thus enables a high speed, compact optical transmitter to be built in a highly cost-efficient package.

The LTC5100 can be operated in standalone mode, or controlled by an external microprocessor via a built-in I2C(TM) Serial Interface port. The LTC5100 has extensive fault detection and eye safety features, including the monitoring of overpower, over-current, under power, and undervoltage.

The LTC5100 operates from a single 3.3V supply. It draws 50 mA of current when transmitting.The LTC5100 is offered in a 4mm x 4mm 16-lead plastic QFN surface mount package, consuming a small PC board space. Pricing starts at $5.15 each in 1,000 piece quantities.

Summary of Features: LTC5100
155Mbps to 3.2Gbps Laser Diode Driver for VCSELs
60ps Rise & Fall Times, 10ps Deterministic Jitter
On-Chip ADC & DACs for Complete Digital Closed-Loop Monitoring & Control of Laser Current & Voltage Over Temperature, to Ensure Low Noise, High Quality Eye Diagrams Across the Modulation Range & Over Temperature
On-Chip Digital Controller for Standalone Operation, or Microprocessor Controlled Digital Setup via I2C(TM) Serial Interface
Built-In Selectable Automatic Power Control or Constant Current Control Modes
Extensive Fault Detection for Laser Eye Safety
Fewest External Components to Fit Small Form Factor Applications

Company Background
Linear Technology Corporation was founded in 1981 as a manufacturer of high performance linear integrated circuits. Linear Technology products include operational, instrumentation and audio amplifiers; voltage regulators,power management devices, DC-DC converters and voltage references; comparators; monolithic filters; communications interface circuits; one-chip data acquisition sub-systems; pulse-width modulators and sample-and-hold devices; and high frequencydevices. Applications for Linear Technology's high performance circuits include wireless and broadband telecommunications infrastructure, cellular telephones, networking products and satellite systems, notebook and desk top computers, computer peripherals, video/multimedia, industrial and medical instrumentation, automotive electronics, factory automation, process control, military and space systems, and high-end consumer products including digital cameras, MP3 players and other electronic products.

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