Precision Clock Generator
The 5T940 generates a high precision FEC (Forward Error Correction)or non-FEC source clock for SONET/SDH systems as well as asource clock for Gigabit Ethernet systems. This device also has clockregeneration capability: it creates a "clean" version of the clock input byusing the internal oscillator to square the input clock's rising and fallingedges and remove jitter. In the event that the main clock input fails, thedevice automatically locks to a backup reference clock using a hitlessswitchover mechanism.This device detects loss of valid CLKIN and leaves the VCO of the PLL atthe last valid frequency while an alternate input REFIN is selected. If CLKINand REFIN are different frequencies, the multiplication factor will be adjusted toretain the same output frequency.The 5T940 can act as a translator from a differential LVPECL, LVDS, orsingle-ended LVTTL input to LVPECL or LVDS outputs. The 5T940-10has LVDS outputs and the 5T940-30 has LVPECL outputs.The three modes of output frequency range are controlled by the SELmode,which is a 3-level pin. When SELmode is high or low, the QOUT is a multipliedversion of the input clock while QREG is a regenerated version of the input clock.When SELmode is mid, the QOUT is a multiplied version of the input clock whileQREG is QOUT/4.The 5T940 features a selectable loop bandwidth.The 5T940 features a selectable loop bandwidth.
- Input frequency:- For SONET non-FEC: 19.44MHz, 38.88MHz, 77.76MHz, 155.52MHz,311.04MHz, or 622.08MHz- For SONET FEC: 20.83MHz, 41.66MHz, 83.31MHz, 166.63MHz,333.26MHz, or 666.52MHz
- - For 10GE copper: 19.53MHz, 39.06MHz, 78.125MHz, 156.25MHz,312.5MHz, or 625MHz
- - For 10GE optical: 20.14MHz, 40.28MHz, 80.56MHz, 161.13MHz,322.26MHz, or 644.53MHz
- 3-level inputs for feedback divide ratio and output frequency rangeselection
- 1x, 2x, 4x, 8x, 16x, and 32x outputs on QOUT
- Regenerated input clock or QOUT/4 on QREG
- Lock indicator
- Power-down modeLVPECL or LVDS outputs
- Three modes of output frequency range- Mode 0: QOUT range 155.5 - 166.6MHz. QREG is a regenerated versionof the input clock.- Mode 1: QOUT range 622 - 666.5MHz. QREG output 155.5-166.6MHz.- Mode 2: QOUT range 622 - 666.5MHz. QREG is a regenerated version- Mode 2: QOUT range 622 - 666.5MHz. QREG is a regenerated versionof the input clock frequency.
- Selectable loop bandwidths
- Hitless switchover
- Differential LVPECL, LVDS, or single-ended LVTTL input interface