Renesas Electronics 8T49N240 FemtoClock® Frequency Translators

The 8T49N240 accepts up to two differential or single-ended input clocks and a fundamental-mode crystal input. The internal PLL can lock to either of the input reference clocks or just to the crystal to behave as a frequency synthesizer. The PLL can use the second input for redundant backup of the primary input reference, but in this case, both input clock references must be integer related in frequency.

The device supports hitless reference switching between input clocks. The device monitors both input clocks for Loss of Signal (LOS) and generates an alarm when an input clock failure is detected. Automatic and manual hitless reference switching options are supported. LOS behavior can be set to support gapped or un-gapped clocks.

The 8T49N240 supports holdover. The holdover has an initial accuracy of ±50ppB from the point where the loss of all applicable input reference(s) has been detected. It maintains a historical average operating point for the PLL that may be returned to holdover at a limited phase slope.

The PLL has a register-selectable loop bandwidth from 0.2Hz to 6.4kHz.

The device supports Output Enable and Clock Select inputs and Lock, Holdover, and LOS status outputs.

The device is programmable through an I²C interface. It also supports I²C master capability to allow the register configuration to be read from an external EEPROM. Factory pre-programmed devices are also available using the on-chip One Time Programmable (OTP) memory.

The Renesas Electronics 8T49N240 FemtoClock® Frequency Translator is available in a 6.0mm x 6.0mm VFQFN-40 package with an exposed pad for increased thermal performance.