JESD204B Compliant Fanout Buffer
and Divider
8V79S680
Datasheet
Description
Features
▪ Supports high-speed, low phase noise converter clocks
The 8V79S680 is a fully integrated, clock and SYSREF signal fanout
buffer for JESD204B applications. It is designed as a high-performance
clock and converter synchronization solution for wireless base station
radio equipment boards with JESD204B subclass 0, 1 and 2
▪ Distribution, fanout, phase-delay of clock and SYSREF signals
▪ Very low output noise floor: -158.8dBc/Hz noise floor
(245.76MHz)
compliance. The main function of the device is the distribution and
fanout of high-frequency clocks and low-frequency system reference
signals generated by a JESB204B clock generator such as the IDT
8V19N480, extending its fanout capabilities and providing additional
phase-delay. The 8V79S680 is optimized to deliver very low phase noise
clocks and precise, phase-adjustable SYSREF synchronization signals
as required in GSM, WCDMA, LTE, LTE-A radio board implementations.
Low-skew outputs, low device-to-device skew characteristics and fast
output rise/fall times help the system design to achieve deterministic
clock and SYSREF phase relationship across devices.
▪ Supports clock frequencies up to 3GHz, including clock output
frequencies of 983.04MHz, 491.52MHz, 245.76MHz and
122.88MHz
▪ 4 output channels with a total of 16 differential outputs, organized
in:
— 8 dedicated clock outputs
— 8 outputs configurable as SYSREF outputs with individual
phase delay stages, or configurable as additional clock outputs
▪ Each channel contains:
The device distributes the input clock (CLK) and JESD204B SYSREF
signals (REF) to four fanout channels. In each channel, both input clock
and SYSREF signals are fanned-out to multiple clock (QCLK) and
SYSREF (QREF) outputs. Clock signals can be frequency-divided in
each channel. Configurable phase-delay circuits are available for both
clock and SYSREF signals. The propagation delays in all signal paths
are fully deterministic to support fixed phase relationships between clock
and SYSREF signals within one device. Clock divider can be bypassed
for low-latency clock paths. The device facilitates synchronization
between frequency dividers within the device and across multiple
devices, removing phase ambiguity introduced in dividers between
power and configuration cycles.
— frequency dividers: ÷1, ÷2, ÷4, ÷6, ÷8, ÷12, ÷16
— clock phase delay circuits
▪ Clock phase delay circuits
— Clock: delay unit is the clock period; 256 steps
— SYSREF: Configurable precision phase delay circuits: 8 steps
of 131ps, 262ps, 393ps or 524ps
▪ Flexible differential outputs:
— LVDS/LVPECL configurable
— Amplitude configurable
— Power-down modes for unused outputs
— Supports DC and AC coupling
Each channel supports clock frequencies up to 3GHz. In an alternative
configuration, for instance JESD204B subclass 0 and 2, the SYSREF
(QREF) outputs can be configured as regular clock outputs adding
additional clock fanout to the device.
— QREF (SYSREF) output pre-bias feature to prevent glitches
when turning output on or off
▪ Supply voltage:
All outputs are very flexible in amplitude configuration, output signal
termination and allow both DC and AC coupling. Outputs can be
disabled and powered-down when not used. The SYSREF output
pre-bias feature supports prevention of power-on glitches and enables
AC-coupling of the system synchronization signals.
— 3.3V core and signal I/O
— 1.8V Digital control SPI I/O (3.3V-tolerant inputs)
▪ 64 VFQFN-P package (9mm x 9mm x 0.85mm)
▪ Ambient temperature range: -40°C to +85°C
The device is configured through a 3-wire SPI serial interface. The
device is packaged in a lead-free (RoHS 6) 64-lead VFQFN package.
The extended temperature range supports wireless infrastructure,
telecommunication and networking end equipment requirements. The
device is a member of the high-performance clock family from IDT.
Typical Applications
▪ JESD204B low phase noise clock and SYSREF signal distribution
▪ Supports JESD204 subclass 0, 1 and 2
▪ Clock distribution device for jitter-sensitive ADC and DAC circuits
▪ Wireless infrastructure
▪ Radar and imaging
▪ Instrumentation and medical
©2016 Integrated Device Technology, Inc.
1
August 4, 2016
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