Description
The 8V19N490 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 wireless base
station radio equipment boards. The device is optimized to deliver
excellent phase noise performance as required in GSM, WCDMA,
LTE, and LTE-A radio board implementations. The device supports
JESD204B subclass 0 and 1 clocks.
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.
The device supports the clock generation of high-frequency clocks
from the selected VCO and low-frequency synchronization signals
(SYSREF). SYSREF signals are internally synchronized to the clock
signals. Delay functions exist for achieving alignment and controlled
phase delay between system reference and clock signals and to
align/delay individual output signals. The four 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 a 3-wire SPI 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 8V19N490 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 with support for JESD204B
▪ Optimized for low-phase noise: -150dBc/Hz (800kHz offset;
245.76MHz clock)
▪ Integrated phase noise of 80fs RMS typical (12kHz–20MHz)
▪ Dual-PLL architecture
▪ First PLL stage with external VCXO for clock jitter attenuation
▪ Second PLL with internal FemtoClock NG PLL: 2949.12MHz
▪ Six output channels with a total of 19 outputs, organized in:
— Four JESD204B channels (device clock and SYSREF output)
with two, four and six outputs
— One clock channel with two outputs
— One VCXO output
▪ Configurable integer clock frequency dividers
▪ Supported clock output frequencies include: 2949.12, 1474.56,
983.04, 491.52, 245.76, and 122.88MHz
▪ Low-power LVPECL/LVDS outputs support configurable signal
amplitude, DC and AC coupling and LVPECL, LVDS line
terminations techniques
▪ Phase delay circuits:
— Clock phase delay with 256 steps of 339ps and a range of 0 to
86.466ns
— Individual SYSREF phase delay with 8 steps of 169ps
— Additional individual SYSREF fine phase delay with 25ps
steps
— Global SYSREF signal delay with 256 steps of 339ps and a
range of 0 to 86.466ns
▪ Redundant input clock architecture with four inputs, including:
— Input activity monitoring
— Manual and automatic, fault-triggered clock selection modes
— Priority controlled clock selection
— Digital holdover and hitless switching
— Differential inputs accept LVDS and LVPECL signals
▪ SYSREF generation modes include internal and external trigger
mode for JESD204B
▪ Supply voltage: 3.3V
▪ SPI and control I/O voltage: 1.8V/3.3V (selectable)
▪ Package: 11  11mm 100-CABGA
▪ Temperature range: -40°C to +85°C