78Q2120C
10/100BASE-TX
Transceiver
DATA SHEET
January 2009
DESCRIPTION
The 78Q2120C is a 10BASE-T/100BASE-TX Fast
Ethernet transceiver. It includes integrated MII,
ENDECs, scrambler/descrambler, dual-speed clock
recovery, and full-featured auto-negotiation function.
The transmitter includes an on-chip pulse-shaper and
a low-power line driver. The receiver has an adaptive
equalizer and a baseline restoration circuit required
for accurate clock and data recovery. The transceiver
interfaces to Category-5 unshielded twisted pair (Cat-
5 UTP) cabling for 100BASE-TX/10BASE-T and
Category-3 unshielded twisted pair for 10BASE-T.
Connection to the line media is via 1:1 isolation
transformers. No external filter is required. Interface
to the MAC is accomplished through an IEEE-802.3
compliant Media Independent Interface (MII). The
product is fabricated in an advanced CMOS process
for high performance and low power operation.
FEATURES
•
10BASE-T/100BASE-TX IEEE-802.3 compliant
TX and RX functions requiring a dual 1:1
isolation transformer interface to the line
Integrated MII, 10BASE-T/100BASE-TX ENDEC,
100BASE-TX scrambler/descrambler, and full-
featured auto-negotiation function
Full duplex operation capable
PCS Bypass supports 5-bit symbol interface
Register-programmable transmit amplitude
Dual speed digital clock recovery
Automatic polarity correction during auto-
negotiation and 10BASE-T signal reception
Power-saving and power-down
including transmitter disable
modes
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LED indicators: LINK, TX, RX, COL, 100, 10,
FDX
User programmable Interrupt pin
64-Pin TQFP (JEDEC LQFP) package
Single 3.3 V
±
0.3V Supply
BLOCK DIAGRAM
4B/5B Encoder,
Scrambler,
Parallel/Serial
100M
NRZ/NRZI
MLT3 Encoder
TX CLK GEN
Pulse Shaper
Pulse Shaper
and Filter
TXOP/N
MDI
RXIP/N
Auto
Negotiation
10M
100M
RX_CLK
TX_CLK
RXD[3:0]
TXD[3:0]
Manchester Decoder,
Parallel/Serial
Serial/Parallel
Descrambler,
5B/4B Decoder
PS
VCC
GND
MII
Registers
&
Interface
Logic
10M
Parallel/Serial,
Manchester Encoder
Manchester Encoder
Carrier Sense,
Collision Detect
Collision Detect
CLK
Recovery
Adaptive EQ,
Baseline Wander Correct,
MLT3 Decode, NRZI/NRZ
MLT3 Decode, NRZI/NRZ
LEDs
Clock Reference
Clock Reference
CKIN
25MHz
LEDL
LEDBTX
LEDTX LEDCOL
LEDBT
LEDFX
LEDRX
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©
2009 Teridian Semiconductor Corporation
Rev 1.3
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
