Description
The 8V19N478 is a fully integrated FemtoClock NG jitter
attenuator and clock synthesizer designed as a high-performance
clock solution for conditioning and frequency/phase management
of 10/40/100/400 Gigabit-Ethernet line cards. The device is
optimized to deliver excellent phase noise performance as
required to drive physical layer devices, and provides the clean
clock frequencies of 625MHz, 500MHz, 312.5MHz, 250MHz,
156.25MHz, and 125MHz.
A two-stage PLL architecture supports both jitter attenuation and
frequency multiplication. The first stage PLL is the jitter attenuator,
and uses an external VCXO for best possible phase noise
characteristics. The second stage PLL locks on the VCXO-PLL
output signal, and synthesizes the target frequency. This PLL has
a VCO circuit at 2500MHz.
The 8V19N478 generates the output clock signals from the VCO
by frequency division. Four independent frequency dividers are
available; three support integer-divider ratios, and one integer as
well as fractional-divider ratios. Delay circuits can be used for
achieving alignment and controlled phase delay between clock
signals. The two redundant inputs are monitored for activity. Four
selectable clock switching modes are provided to handle clock
input failure scenarios. Auto-lock, individually programmable
output frequency dividers, and phase adjustment capabilities are
added for flexibility.
The device is configured through an I2
C interface and reports lock
and signal loss status in internal registers and via a lock detect
(LOCK) output. Internal status bit changes can also be reported
via the nINT output. The device is ideal for driving converter
circuits in wireless infrastructure, radar/imaging, and
instrumentation/medical applications. The device is a member of
the high-performance clock family from IDT.

Features
▪ High-performance clock RF-PLL:
• Optimized for low phase noise: -157.7dBc/Hz (1MHz offset;
156.25MHz clock), design target
• Integrated phase noise, RMS (12kHz–20MHz): 73fs
(typical), design target
▪ Dual-PLL architecture:
• 1st-PLL stage with external VCXO for clock jitter attenuation
• 2nd-PLL stage with internal FemtoClock NG PLL at
2500MHz
▪ Four output banks with a total of 18 outputs, organized in:
• Three clock banks with one integer frequency divider and
four differential outputs
• One clock bank with one fractional divider and six
differential outputs
• One VCXO-PLL output bank with one selectable LVDS and
two LVCMOS outputs
▪ Four output banks contain a phase delay circuit with steps of
the VCO clock period (400ps)
▪ Supported clock output frequencies include:
• From the integer dividers: 2500MHz, 1250MHz, 625MHz,
500MHz, 312.5MHz, 250MHz, 156.25MHz, and 125MHz
• From the fractional divider: 80–300MHz
▪ Low-power LVPECL and LVDS outputs support configurable
signal amplitude, DC and AC coupling, and LVPECL, LVDS,
and line termination techniques
▪ Redundant input clock architecture:
• Two inputs
• Individual input signal monitor
• Digital holdover
• Manual and automatic clock selection
• Hitless switching
▪ Status monitoring and fault reporting:
• Input signal status
• Hold-over and reference loss status
• Lock status with one status pin
• Mask-able status interrupt pin
▪ Voltage supply:
• Device core supply voltage: 3.3V
• Output supply voltage: 3.3V, 2.5V, or 1.8V
• I/O voltage: 1.8V or 3.3V (selectable), and 3.3V tolerant
inputs when set to 1.8V
▪ Package: 11  11  1 mm ball pitch 100-FPBGA
▪ Temperature range: -40°C to +85°C