SFP+ controller with digital LDD interface
The DS1878T+ is an SFP+ controller from Analog Devices that integrates a digital laser-diode driver (LDD) interface, handling both analog and digital input types and outputting a digital signal for closed-loop control of the SFP+ transceiver bias and modulation. Its 2.5 mA supply current keeps the controller's own draw low enough that the SFP+ module's total power budget — typically capped at 1.5 W per the SFF-8431 specification — is not eaten by the control logic, leaving headroom for the laser driver and TIA. Rated for operation from -40°C to 95°C, the part covers the industrial temperature band plus a 10°C margin above the standard 85°C, useful in outdoor or poorly ventilated OLT/ONU equipment where the module ambient settles above 85°C.
Package and board-fit for 28-TQFN
The DS1878T+ is supplied in a 28-lead TQFN package (5x5 mm body, 0.50 mm pitch) with an exposed pad — the same footprint as the 28-WFQFN variant, so the PCB land pattern is shared across both order codes. Without adequate thermal relief under the pad, the junction temperature will rise above the 95°C ambient ceiling even at the 2.5 mA supply current.