CXB1818Q

The CXB1818Q is a high-speed monolithic Laser Diode Driver/Current Switch with ECL/PECL input level. Open collector outputs are provided at the output pins (Q, QBX) and have the capacity of driving modulation current of 50mAp-p at a maximum data rate of 622Mbps. Along with the modulation current generator there is the laser diode bias current generator which has capacity of sourcing up to 60mA (Bias). The laser diode bias current CXB1818Q can be controlled by either a voltage or current into the bias adjust pin (BiasAdj) and the bias set pin (SBias), depending on
how these pins CXB1818Q are configured. Control of the bias current is achieved through the APC (Automatic Power Control) circuit. In order to avoid having a large current go through the laser diode, this IC also provides an Activity detector function for laser protection. The Activity detector circuit detects data edge transitions and if no data transition occurs after a certain period, then both the modulation and bias currents are shutdown. The bias currents are shut it
down by in order to pull down the output voltage of APC OP.Amp.

When the automatic shutdown CXB1818Q is conducted, it is possible to select whether the laser diode alarm output is activated or not. Additionally, this IC has the DFF for the input signal correction and the internal Duty Cycle correction circuit that can control the falling edge of the input pulse up to a maximum of 1.0ns(Min.).