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ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User
Guide
The ONET4201LD and ONET4211LD are laser drivers for fiber optic applications up to 4.25Gbps.
The ONET4201LD has active back termination at the outputs while the ONET4211LD has standard
terminations. All other functionality between the devices is the same. The laser drivers accept CML
input data and provide bias and modulation currents for driving a laser diode. Laser bias current
automatic power control (APC), temperature compensation of modulation current, fault detection,
and current monitor features are also provided. The laser drivers have two fault modes: hard-fault
and soft-fault. In hard-fault mode, the bias and modulation currents are disabled when a fault is
detected. In soft-fault mode, the fault detection flag is set but the bias and modulation currents are
not disabled.
The evaluation module (EVM) is designed to demonstrate the electrical performance of the devices.
1
Rev. A September 2005
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Related Manuals for Texas Instruments ONET4201LD
Summary of Contents for Texas Instruments ONET4201LD
- Page 1 ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide The ONET4201LD and ONET4211LD are laser drivers for fiber optic applications up to 4.25Gbps. The ONET4201LD has active back termination at the outputs while the ONET4211LD has standard terminations. All other functionality between the devices is the same. The laser drivers accept CML input data and provide bias and modulation currents for driving a laser diode.
- Page 2 Figure 3: Bias and Modulation Current Adjustment Potentiometers in APC Mode ........7 Figure 4: ONET4201LD/ONET4211LD Schematic....................8 Figure 5: ONET4201LD at 4.25Gbps with K28.5 Pattern, I = 40mA ............9 Figure 6: ONET4201LD at 2.125Gbps with K28.5 Pattern, I = 40mA ............
- Page 3 2.1. Open Loop Mode (APC Disabled) with Soft Fault The ONET4201LD and ONET4211LD have automatic power control to maintain a constant bias current with temperature and aging. When actually driving a laser, this is typically done by connecting the output of the laser monitor photodiode to PD (pin 19). The EVM includes a photodiode emulation circuit that, when enabled, will source a pseudo photodiode current to PD.
- Page 4 Rotate potentiometers P3 (fine adjust) and P4 (course adjust) fully clockwise to set the MONB fault point at its lowest level. Figure 2: Bias and Modulation Current Adjustment Potentiometers for Open Loop Operation ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide Rev. A September 2005...
- Page 5 P38. The modulation current can be directly read from the VCC_IMOD_2 power supply or using an ammeter. SDOWN LED D2 should be off. Rev. A September, 2005 ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide...
- Page 6 Rotate potentiometers P1 (fine adjust) and P2 (course adjust) fully counterclockwise to set the MONP fault point at its highest level, avoiding a fault triggered by high photodiode current. ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide Rev. A September 2005...
- Page 7 Once the reason for the fault has been corrected, the device fault condition can be cleared by pressing and releasing the disable pushbutton SW2. For more detailed information on the operation of the ONET4201LD or ONET4211LD, please refer to the respective data sheet.
- Page 8 Serial Link Products 3. Schematic Figure 4: ONET4201LD/ONET4211LD Schematic ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide Rev. A September 2005...
- Page 9 Serial Link Products 4. Measurement Results Figure 5: ONET4201LD at 4.25Gbps with K28.5 Pattern, I = 40mA Figure 6: ONET4201LD at 2.125Gbps with K28.5 Pattern, I = 40mA Rev. A September, 2005 ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide...
- Page 10 Serial Link Products Figure 7: ONET4201LD at 1.0625Gbps with K28.5 Pattern, I = 40mA ONET4201LD/ONET4211LD 4.25Gbps Laser Driver EVM User Guide Rev. A September 2005...
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