Maxim intros optical controller for GPON transceivers

May 29, 2007
MAY 29, 2007 -- The DS1865 integrates GPON power-leveling functionality, a laser bias average-power-control loop, video amplifier control, and SFF-8472 diagnostic and alarm features.

MAY 29, 2007 -- Maxim Integrated Products (search for Maxim) has introduced the DS1865, an optical control, calibration, and monitor IC. The DS1865 integrates GPON power-leveling functionality, a laser bias average-power-control (APC) loop, video amplifier control, and SFF-8472 diagnostic and alarm features. These capabilities make the DS1865 an excellent choice for all BPON and GPON triplexer applications, Maxim believes.

In the past a laser-diode driver intended for GPON transceiver applications needed to include the laser-bias APC loop or lookup table (LUT), some fault management circuitry to meet eye-safety requirements, and other control functionality. These additional features added extra complexity to a design and were expensive to implement in the high-speed processes required to meet the GPON specifications, Maxim says.

The DS1865 controller, however, is optimized to work with the MAX3643 burst-mode laser driver for a compact GPON system design. The DS1865 is based on CMOS technology. Implementing all control, monitoring, and fault management functions in a CMOS process minimizes the total cost for a GPON transceiver, Maxim says.

The DS1865 optical controller also integrates several analog functions that make the device's performance the best in its class, according to Maxim. An integrated 13-bit ADC includes input scaling, which provides 29 dB of dynamic range. The built-in temperature sensor is factory-calibrated and has 50% less error than competing devices in the developer's estimation. A tracking error lookup table enables compensation for laser-monitor diode error that occurs across temperature. This latter feature further increases the accuracy of the laser power control.

The DS1865 includes a 13-bit laser-bias DAC, which Maxim asserts is more than four times better than existing devices, to control the video amplifier and a second DAC to control the boost converter (MAX5026) for the APD bias. The APD bias can be controlled across temperature to ensure that the APD operates in the correct gain range. The RF output power of the video amplifier (MAX3654) is controlled using the MAX4003 to sense the output RF power, an op amp to make a feedback loop, and the DS1865's DAC output to provide a set point for the control loop.

The built-in capability enables the DS1865 to simplify GPON transceiver design in several ways. The APC loop controls the laser's bias across temperature and aging, thus removing the requirement for a laser-bias LUT. The modulation control DAC and APC loop have eight bits of resolution and another three levels of scaling: +0 dB, -3 dB, and -6 dB. This scaling ability enables a single register to control the ONU power level. The DS1865 memory map conforms to SFF-8472 specification, making this device simple to use and design in.

The DS1865 is available now in a 28-pin 5x5-mm TQFN. It operates from a 2.85-V to 5.5-V power supply over a -40 degrees Celsius to +95 degrees Celsius temperature range, and is priced at $1.98 (10k-up, FOB USA). An evaluation kit is available.

Also available is the DS1863 burst-mode PON controller, which does not include the additional DACs for video amplifier and APD bias control. The DS1863 is available in a 16-pin TSSOP package, and is priced at $1.55 (10k-up, FOB USA). An evaluation kit is available.

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