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DS1873 Analog LDD interface SFP+ controller

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DS1873 Analog LDD interface SFP+ controller

DS1873 - Basic Description

The DS1873 controls and monitors all functions for SFF, SFP, and SFP+ modules including all SFF-8472 functionality. The DS1873 provides APC loop, modulation current control, and eye safety functionality. The DS1873 continuously monitors for high output current, high bias current, and low and high transmit power to ensure that laser shutdown for eye safety requirements are met without adding external components. Six ADC channels monitor VCC, temperature, and four external monitor inputs (MON1–MON4) that can be used to meet all monitoring requirements. MON3 is differential with support for common mode to VCC. Two digital-to-analog (DAC) outputs with temperatureindexed lookup tables (LUTs) are available for additional monitoring and control functionality. The DS1873 integrates the control and monitoring functionality required to implement an SFP or SFP+ system.

Features - DS1873

♦ Meets All SFF-8472 Control and Monitoring Requirements
♦ Four 10-Bit Delta-Sigma Outputs with 36 Entry Temperature LUTs Laser Bias Controlled by APC Loop and Temperature LUT to Compensate for Tracking Error Laser Modulation Controlled by 72-Entry Temperature LUT Two Additional DACs Controlled by One 72-Entry and One 36-Entry Temperature LUT
♦ Digital I/O Pins: Five Inputs, Five Outputs
♦ Comprehensive Fault-Measurement System with Maskable Laser Shutdown Capability
♦ Flexible, Two-Level Password Scheme Provides
Three Levels of Security
♦ 120 Bytes of Password-1 Protected Memory
♦ 128 Bytes of Password-2 Protected Memory in Main Device Address
♦ 256 Additional Bytes Located at A0h Slave Address
♦ I2C-Compatible Interface
♦ +2.85V to +3.9V Operating Voltage Range
♦ -40°C to +95°C Operating Temperature Range
♦ 28-Pin TQFN (5mm x 5mm) Package

Information useful for application

Power-Supply Decoupling:
To achieve best results, it is recommended that the power supply is decoupled with a 0.01μF or a 0.1μF capacitor. Use high-quality, ceramic, surface-mount capacitors, and mount the capacitors as close as possible to the VCC and GND pins to minimize lead inductance.

SDA and SCL Pullup Resistors:
SDA is an open-collector output on the DS1873 that requires a pullup resistor to realize high logic levels. A master using either an open-collector output with a pullup resistor or a push-pull output driver can be utilized for SCL. Pullup resistor values should be chosen to ensure that the rise and fall times listed in the I2C AC Electrical Characteristics table are within specification.


♦SFF, SFP, and SFP+ Transceiver Modules


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