PM8620 datasheet(45/190 Pages) PMC

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NSE-20G™ Standard Product Data Sheet

Preliminary

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

Document ID: PMC-2000170, Issue 3

The LVDS system is comprised of the LVDS Receiver (RXLV), LVDS Transmitter (TXLV), ),

Transmitter reference (TXREF), data recovery unit (DRU), parallel to serial converter (PISO and

Clock Synthesis Unit (CSU).

9.1.1

LVDS Receiver (RXLV)

The RXLV block is a 777.6 Mbit/s Low Voltage Differential Signaling (LVDS) Receiver

according to the IEEE 1596.3-1996 LVDS Specification.

The RXLV block is the receiver in Figure 8, accepting 777.6 Mbit/s LVDS signals from the

transmitter, over RP[X]/RN[X] pins, amplifying them and converting them to digital signals, then

passing them to a data recovery unit (DRU). Holding to the IEEE 1596.3-1996 specification, the

RXLV has a differential input sensitivity better than 100 mV, and includes at least 25 mV of

hysteresis. There are 32 RXLV blocks in the NSE.

9.1.2

LVDS Transmitter (TXLV)

The TXLV block is a 777.6 Mbit/s Low voltage Differential Signaling (LVDS) Transmitter

according to the IEEE 1596.3-1996 LVDS Specification.

The TXLV accepts 777.6 Mbit/s differential data from a “parallel-in, serial-out” (PISO) circuit

and then transmits the data off-chip as a low voltage differential signal on TP[X]/TN[X] pins.

The TXLV uses a reference current and voltage from the TXREF block to control the output

differential voltage amplitude and the output common-mode voltage.

There are 32 instances of the TXLV block in the NSE-20G.

9.1.3

LVDS Transmit Reference (TXREF)

The TXREF provides an on-chip bandgap voltage reference (1.20 V ±5%) and a precision current

to the TXLV (777.6 Mbit/s LVDS Transmitter) block’s. The reference voltage is used to control

the common-mode level of the TXLV output, while the reference current is used to control the

output amplitude.

The precision currents are generated by forcing the reference voltage across an external, off-chip

3.16 k

Ω(±1%) resistor. The resulting current is then mirrored through several individual reference

current outputs, so each TXLV receives its own reference current.

There are two instances of the TXREF in the NSE-20G.

9.1.4

Data Recovery Unit (DRU)

The DRU is a fully integrated data recovery and serial to parallel converter that can be used for

777.6 Mbit/s NRZ data. 8B/10B block code is used to guarantee transition density for optimal

performance.

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