XRT91L80 Просмотр технического описания (PDF) - Exar Corporation
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XRT91L80 Datasheet PDF : 45 Pages
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REV. P1.1.0
TRANSMITTER SECTION
NAME
LEVEL
ALTFREQSEL
LVTTL,
LVCMOS
VCXO_SEL
LVTTL,
LVCMOS
VCXO_LOCK
LVCMOS
VCXO_LOCKEN
LVTTL,
LVCMOS
CPOUT
LOOPBW
-
LVTTL,
LVCMOS
TXPCLKOP
TXPCLKON
LVDS
PRELIMINARY
XRT91L80
2.488/2.666 GBPS STS-48/STM-16 SONET/SDH TRANSCEIVER
TYPE
I
I
O
I
O
I
O
PIN
DESCRIPTION
P1 Reference Clock Frequency Select
This pin is used to select the frequency of the REFCLKP/N
clock input to the CMU.
"Low" = 77.76 MHz (83.31 MHz for FEC)
"High" = 155.52 MHz (166.63 MHz for FEC)
This pin is provided with an internal pull-up.
M6 De-Jitter VCXO Select Option
This pin selects either the normal REFCLKP/N or the de-jitter
VCXO_INP/N pin as a reference clock to the CMU.
"Low" = Normal REFCLKP/N reference clock
"High" = De-Jitter VCXO_INP/N reference clock
This pin is provided with an internal pull-down.
N8 De-Jitter PLL Lock Detect
If the de-jitter PLL lock detect is enabled with pin P3 and the de-
jitter VCXO mode is selected by pin M6, this pin will assert
"High" when the PLL is locked.
"Low" = VCXO Out of Lock
"High" = VCXO Locked
P3 De-Jitter PLL Lock Detect Enable
This pin enables the VCXO_INP/N lock detect circuit and
VCXO_LOCK pin N8 to be active.
"Low" = VCXO Lock Detect Disabled
"High" = VCXO Lock Detect Enabled
This pin is provided with an internal pull-down.
P8 Charge Pump Output (for external VCXO)
The nominal output of the charge pump current is 250µA
M7 CMU Loop Bandwidth Select
This pin is used to select the bandwidth of the clock multiplier
unit of the transmit path to a narrow or wide band. Use Wide
Band for clean reference signals and Narrow Band for noisy ref-
erences.
"Low" = Wide Band (4x)
"High" = Narrow Band (1x)
This pin is provided with an internal pull-down.
P10 Transmit Parallel Clock Output
P11 This 622.08 MHz clock can be used for the downstream device
to generate the TXDI[3:0]P/N data and TXPCLKIP/N clock
input. This enables the downstream device and the STS-48/
STM-16 transceiver to be in synchronization.
NOTE: The XRT91L80 can output a 666.51 MHz transmit clock
output for Forward Error Correction (FEC).
7
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