ONET4201LD Datasheet, PDF (2/26 Pages) Texas Instruments – 155-Mbps to 4.25-Gbps LASER DRIVER

ONET4201LD
SLLS677 – NOVEMBER 2005
www.ti.com
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.
DETAILED DESCRIPTION
BLOCK DIAGRAM
A simplified block diagram of the ONET4201LD 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 below.
OUTPOL
DIN+
DIN–
Input Buffer Stage
Current Modulator
MODSET
MODTC
IBMAX
Modulation Current Generator
MODSET
MODCTRL
MODTC
IMODEN IMODMON
OUT+ OUT–
Active Termination
Bias Current Generator
IBMAX
BIAS
VCC
GND
DISABLE
FLTMODE
4
VCC _Reference
Voltage
3
and Bias
GND ^Generation
IBEN IBMON IBSET ^MONB
Automatic Power Control
(APC)
IMODEN IMODMON IBEN IBMON
IBSET
CAPC
MONP
DISABLE
Control
APCCTRL
APCMON
APCCTRL
PD
APCMON APCSET
FLTMODE
SDOWN
MOD+
MOD–
BIAS
MONB
CAPC
MONP
PD
APCSET
SDOWN
Figure 1. Simplified Block Diagram of the ONET4201LD
B0092-02
2
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