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Dallas controller ICs monitor SFF optical transceivers

Posted: 27 Jan 2003 ?? ?Print Version ?Bookmark and Share

Keywords:dallas semiconductor? ds1854? ds1857? ds1858? optical transceiver controller?

The DS1854, DS1857, and DS1858 integrated optical controller-monitors from Dallas Semiconductor Corp. control laser-driver bias and modulation currents, and manage system-monitoring functions required for SFF-847-compatbile optical transceivers.

Control functionality is comprised of two 256-position, nonvolatile variable resistors with temperature indexed look-up tables. To control bias and modulation currents, the module designer determines the desired value for each resistor across temperature in 20C intervals and stores the data in the on-chip EEPROM look-up tables.

The devices then measure temperature, check readings against the EEPROM look-up table, and adjust resistance automatically.

The DS1854, DS1857, and DS1858 provide monitoring through an integrated 12-bit ADC and temperature sensor, monitoring two or three external analog signals, as well as Vcc and temperature. Programmable alarm trip points for all monitored signals enable the device to alert the system to out-of-tolerance conditions.

The devices also have a flexible EEPROM-addressing architecture, allowing the user to set the memory in different configurations. They can be configured to support 128 bytes each of GBIC/SFP MSA memory and SFF-8472 memory. They can also be configured to support 256 bytes of SFF-8472 memory only.

The monitors communicate over a 2-wire serial interface. The DS1854 and DS1857 also provide a resistor-disable control input for open-circuiting the two variable resistors. In addition, the DS1857 provides an input for an external temperature sensor and three address inputs that allow up to eight devices on a common serial bus.

The DS1854, DS1857, and DS1858 are packaged in a 4-by-4mm BGA and a 16-pin TSSOP. They operate from a 2.7V to 5.5V supply over a -400C to 950C temperature range.

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