APPLICATION NOTE 3790

MAX3967A: Improving Speed Performance of Slow LEDs Using the MAX3967A with Added Peaking Elements


Abstract: This application note presents a simple shunt peaking technique that significantly improves LED eye quality and edge speed. The use of Long Wave LEDs is particularly attractive for low data rate, low power applications where cost is a critical parameter. The MAX3967A is a programmable LED driver for fiber optic transmitters operating at data rates up to 270Mbps. The circuit contains a high-speed current driver with programmable temperature coefficient (tempco), adjustments for LED pre-bias voltage, and a disable feature. The circuit accepts PECL data inputs, and operates from a single +2.97V to +5.5V power supply. The SFP LED driver can switch up to 100mA into typical high-speed light-emitting diodes. The modulation current is programmed with a single external resistor. As temperature increases, the device's modulation current increases with a tempco that is programmable from 2500ppm/°C to 12,000ppm/°C. The large modulation current capability makes the MAX3967 a good candidate for exchanging drive for an improved response time.