NB3W800L
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12
SIGNAL AND FEATURE OPERATION
CLK_IN, CLK_IN#
The differential input clock is expected to be sourced from
a clock synthesizer with an HCSL−compatible output, e.g.
CK420BQ, CK−NET, CK−uS, or CK509B or another
driver.
OE# and Output Enables (Control Registers)
Each output can be individually enabled or disabled by
SMBus control register bits. Additionally, each output of the
DIF[7:0] has a dedicated OE# pin. The OE# pins are
asynchronous asserted−low signals. The Output Enable bits
in the SMBus registers are active high and are set to enable
by default.
The disabled state for the NB3W800L low power NMOS
Push−Pull outputs is Low/Low.
Please note that the logic level for assertion or deassertion
is different in software than it is on hardware. Output is
enabled if OE# pin is pulled low and still maintains software
programming logic with output enabled if OE register is true.
The assertion and de−assertion of this signal is absolutely
asynchronous.
OE# Assertion (Transition from ‘1’ to ‘0’)
All differential outputs that were tristated will resume
normal operation in a glitch free manner.
OE# De−Assertion (Transition from ‘0’ to ‘1’)
Corresponding output will transition from normal
operation to tri−state in a glitch free manner.
100M_133M# − Frequency Selection
The 100M_133M# is a hardware pin, which programs the
appropriate output frequency of the DIF pairs. Note that the
CLK_IN frequency is equal to CLK_OUT frequency. An
external pull−up or pull−down resistor is attached to this pin
to select the input/output frequency.
PWRGD/PWRDN#
PWRGD/PWRDN# is a dual function pin. PWRGD is
asserted high and de−asserted low. De−assertion of PWRGD
(pulling the signal low) is equivalent to indicating a
powerdown condition. PWRGD (assertion) is used by the
NB3W800L to sample initial configurations such as
frequency select condition and SA selections.
After PWRGD has been asserted high for the first time,
the pin becomes a PWRDN# (Power Down) pin that can be
used to shut off all clocks cleanly and instruct the device to
invoke power savings mode. PWRDN# is a completely
asynchronous active low input. When entering power
savings mode, PWRDN# should be asserted low prior to
shutting off the input clock or power to ensure all clocks
shut down in a glitch free manner. When PWRDN# is
asserted low by two consecutive rising edges of DIF#, all
differential outputs are held tri−stated on the next DIF# high
to low transition. The assertion and de-assertion of
PWRDN# is absolutely asynchronous.
WARNING: Disabling of the CLK_IN input clock prior
to assertion of PWRDN# is an undefined
mode and not recommended. Operation in
this mode may result in glitches, excessive
frequency shifting, etc.
Table 18. PWRGD/PWRDN# FUNCTIONALITY
PWRGD/PWRDN# DIF DIF#
0 Tri−state Tri−state
1 Running Running
HBW_BYPASS_LBW#
The HBW_BYPASS_LBW# is a tri level function input
pin. It is used to select between PLL high bandwidth, bypass
mode and PLL low bandwidth mode.
POWER FILTERING EXAMPLE
V3P3
FB1
R1
VDDA
Place at pin
VDD for PLL
FERRITE
2.2
C9
1 mF
C7
0.1 mF
R2
2.2
C10
1
mF
VDDR
C8
0.1 mF
VDD for Input Receiver
C5
0.1 mF
VDD_DIF
C6
0.1 mF
C1
10 mF
C2
0.1 mF
C4
0.1 mF
C3
0.1 mF
C5
0.1 mF
C6
0.1 mF
Figure 7. Schematic Example of the NB3W800L Power Filtering
VDD_DIF
