When designing multisource agreement
(MSA) optical transceiver modules such
as SFP and SFP+, you need a superior
compact laser driver and a photo diode
amplifier to provide the performance
expected in 10-Gbit/s applications.
Maxim Integrated Products’ MAX3798
gets the job done (see the figure). Expected
uses include 1/2/4/8-Gbit/s Fibre
Channel and 10G Ethernet (10GE)
including 10GBaseSR, 10GBaseLR, and
10GBaseLRM. Speeds to 10.32 Gbits/s
using NRZ are possible.
The receiver amplifier takes the signal
from the PIN photo diode and transimpedance
amplifier in differential form
and limits it into a CML-level differential output. Typical receiver sensitivity
is 3 mV p-p. The laser
driver is designed for use with
vertical-cavity surface-emitting
lasers (VCSELs) operating at
1310 nm. The VCSEL driver
provides for modulation and
bias current adjustment.
The average optical power is
controlled by an average power
control (APC) loop implemented
by a controller that
interfaces to the VCSEL driver
through a three-wire interface.
The three-wire interface permits
a wide range of advanced
RX and TX modes and settings.
On-chip digital-to-analog
converters (DACs) allow
the use of an external controller
to program the functions
desired.
The MAX3798 is available
in a 32-pin, 5- by 5-mm thin
quad flat no-lead (TQFN)
package. Prices for the device
start at $6.18 in quantities of
10,000 or more.
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