Datasheet

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DETAILED DESCRIPTION
BLOCK DIAGRAM
B0092-01
VCC
GND
DIN+
DIN–
MOD+
MOD–
MODSET
CurrentModulator
OUTPOL
MODTC
BIAS
MONB
IBMAX
MONP
PD
APCSET
SDOWN
DISABLE
CAPC
FLTMODE
InputBufferStage
ModulationCurrentGenerator
MODCTRLMODSET
IMODEN
MODTC
IMODMON
Reference
Voltage
andBias
Generation
VCC
GND
4
3
BiasCurrentGenerator
BIASIBMAX
IBEN IBMON IBSET
MONB
Control
IMODEN IMODMON
IBEN
IBMON
DISABLE
SDOWN
APCCTRL
APCMON
FLTMODE
AutomaticPowerControl
(APC)
IBSET
APCMON
APCCTRL
MONP
APCSET
PD
CAPC
ONET4211LD
SLLS688A – NOVEMBER 2005 – REVISED SEPTEMBER 2007
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
A simplified block diagram of the ONET4211LD is shown in Figure 1 .
This compact, low-power, 4.25-Gbps laser driver circuit consists of a high-speed data path and a
bias-and-control block.
The function of the data path is to buffer the input data and then modulate the laser diode current according to
the input data stream.
The bias-and-control block generates the laser diode bias current, contains automatic power control (APC) to
maintain constant optical output power, generates a modulation current that can be temperature compensated,
and controls power on during start-up and shutdown after failure detection. The circuit design is optimized for
high-speed and low-voltage operation (3.3 V).
The main circuit blocks are described in detail in the following paragraphs.
Figure 1. Simplified Block Diagram of the ONET4211LD
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Product Folder Link(s): ONET4211LD