SNLU245 February   2019 ONET1130EC

 

  1.   ONET1130EC-EVM 11.7-Gbps transceiver with dual CDRs and modulator user’s guide
    1.     Trademarks
    2. 1 Hardware and Equipment
    3. 2 EVM Block Diagram
    4. 3 EVM Connections
    5. 4 Measurement Setup
      1. 4.1 USB2ANY GUI Installation
      2. 4.2 Open-Loop Operation Without Fault Detection or Digital Monitoring
      3. 4.3 Closed-Loop Operation With Fault Detection and Digital Monitoring
    6. 5 LED Indicators
    7. 6 Typical Performance Results
    8. 7 Schematics
    9. 8 ONET1130EC-EVM PCB Layout
    10. 9 Bill of Material

4.3 Closed-Loop Operation With Fault Detection and Digital Monitoring

  1. Place a jumper between pins 1 and 2 of JMP26 to supply -2.5V to the photodiode current mirror to configure the part for automatic power control with digital monitoring and fault detection.
  2. Go to the Core Configuration page.
  3. Disable the laser bias current to prevent a fault from occurring when the Fault Detection is enabled: Reg 0x01[2] = 0'b
  4. Enable the Fault Detection (Reg 0x01[3] = 1'b) and enable the Fault Trigger on MONP Pin (Reg 0x01[7] = 1'b).
  5. Set the TX Bias Current Control to Closed Loop (Reg 0x01[4] = 0'b) and initially use the default 770uA photodiode current range (Reg 0x01[6:5] = 00'b).
  6. Enable the laser bias current: Reg 0x01[2] = 1'b
  7. Enable the ADC (Reg 0x03[7] = 1'b) and ADC oscillator (Reg 0x03[6] = 1'b) in the Analog to Digital Conversion box and select the desired parameter to be monitored using reg 0x03[2:0]).
  8. Set the bias current monitor fault threshold and power monitor fault threshold to max: TXBMF[7:0] Reg 0x11 = TXPMF[7:0] Reg 0x12 = 0xFF. To enable fault detection for these two conditions, set Reg 0x10 [6:5] = 11'b.
  9. Select Digital Bias Current and Digital Photodiode current: Reg 0x10 [6:5] = 11'b.
  10. Set the TX Output Mode to Single-Ended (OUTP): Reg 0x0D[6] = 1'b.
  11. Set the desired TX laser bias current, transmitter modulation current, and TX cross point: Reg 0x0F[7:0] = 0x60, 0x0C[7:0] = 0x50, 0x0E[7:0] = 0xAF
  12. Reduce bias current monitor fault threshold TXBMF[7:0] Reg 0x11 until fault occurs. When the TX_FLT goes high, increase TXBMF[7:0] by at least 16 steps.
  13. Toggle the enable laser bias current by setting Reg 0x01[2] = 0'b followed by Reg 0x01[2] = 1'b to clear the fault and restore the transmit output.
  14. Reduce the power fault threshold TXPMF[7:0] Reg 0x12 until a fault occurs. Increase the power fault threshold level by at least 16 steps.
  15. Toggle the enable laser bias current by setting Reg 0x01[2] = 0'b followed by Reg 0x01[2] = 1'b to clear the fault and restore the transmit output.
  16. Read Reg 0x28[9:2] and Reg 0x29[1:0] content to read the value from the ADC source.