Data centers are gradually adding 40-Gbit/s capability as their 10-Gbit/s traffic increases and aggregation needs expand. However, power consumption is inhibiting that growth. The MAX3948 laser driver-controller chipset from Maxim Integrated Products, though, provides four lanes of 11.3-Gbit/s laser driver capability to boost data handling speed while holding the line on power consumption.
The 40-Gbit/s technology of choice is Ethernet 40GBASE-LR4 QSFP+. The MAX3948 fits this technology as well as Fibre Channel and Sonet. The chipset’s quad small form-factor plugable plus (QSFP+) modules supply four times the data throughput in only one and a half times the area of a single-channel SFP+ module. The chipset also enables the QSFP+ modules to consume less power per channel than a single SFP+ module.
The MAX3948 has a single-channel power consumption of 383 mW at 3.3 V. The resulting power consumption of a four-channel driver is less than 2 W. This enables a QSFP+ module with a power of less than 3.5 W. The lower power consumption is the outcome of the dc-coupled laser driver, which is a patent pending feature.
The other key part of the chipset is the Maxim DS4830 optical microcontroller. Optimized for use in optical transceivers, this 16-bit processor provides a complete optical module control, calibration, and monitoring solution with low power consumption. It also offers an on-chip 13-bit analog-to-digital converter (ADC) and dedicated round-robin offloads. The processor’s single-cycle DSP multiply accumulate (MAC) capability readily implements filters and can maintain four average power control (APC) loops while consuming minimal power.
The figure shows one channel of the MAX3948 driver and the transmit optical subassembly (TOSA) along with the connections to the DS4830 optical microcontroller. Note the optical diode sensor in the TOSA that provides laser output monitoring capability.
The Maxim MAX3948 four-channel laser driver and the DS4830 optical microcontroller form a complete chipset for implementing a 40-Gbit/s QSFP+ optical module. Only one channel of the driver is shown.
The MAX3948 laser driver comes in a 3- by 3-mm, 16-pin thin quad flat no-leads (TQFN) package, and pricing starts at $5 for quantities or 1000 or more. The DS4830 comes in a 5- by 5-mm 40-pin TQFN package. Its pricing begins at $2.85 in quantities of 1000 or more.
