Datasheet

Detailed Description
The MAX3982 comprises a PC board receiver, a cable
driver, and a loss-of-signal detector with adjustable
threshold (Figure 4). Equalization is provided in the
receiver. Selectable preemphasis and selectable output
amplitude are included in the transmitter. The MAX3982
also includes transmit disable control for the output.
PC Board Receiver and Cable Driver
Data is fed into the MAX3982 through a CML input
stage and fixed equalization stage. The fixed equalizer
in the receiver corrects for up to 10in of PC board loss
on FR4 material at 4.25Gbps.
The cable driver includes four-state preemphasis to
compensate for up to 15m of 24AWG, 100Ω balanced
cable. Table 1 is provided for easy translation between
preemphasis expressions. The OUTLEV pin selects the
output amplitude. When OUTLEV is low, the amplitude
is 1200mV
P-P
. When OUTLEV is high, the amplitude is
1600mV
P-P
. Residual jitter of the MAX3982 is indepen-
dent of up to 0.20UI
P-P
source jitter.
Loss-of-Signal (LOS) Output
Loss-of-signal detection is provided on the data input.
Pullup resistors should be connected from LOS to a
supply in the range of +3.0V to +5.5V. The LOS output
is not valid until power-up is complete. Typical LOS
response time is 100ns.
The LOS assert and deassert levels are set by the
LOSLEV pin. When LOSLEV is LVTTL high or open, the
LOS assert threshold is 180mV
P-P
. When LOSLEV is
LVTTL low, the LOS assert threshold is 85mV
P-P
.
TX Disable
Transmit disable is provided to turn off the output when
desired. The TX_DISABLE pin can be connected to
LOS to automatically squelch the output when the
incoming signal is below the threshold set by LOSLEV
(see the Autodetect section).
MAX3982
SFP Copper-Cable Preemphasis Driver
______________________________________________________________________________________ 11
Figure 4. Functional Diagram
MAX3982
OUT+
OUT-
2
V
CC2
LVTTL
CML
FIXED
EQUALIZER
IN-
IN+
TX_DISABLE
V
CC1
PE0
PE1
10kΩ
LIMITER
OUTLEV
LOSLEV
LVTTL
PREEMPHASIS
LOS
SIGNAL DETECT
GND
CML
2
V
CC2
V
CC2
40kΩ
V
CC1
V
CC1
LVTTL
10kΩ
V
CC2
V
CC2
LVTTL
40kΩ
V
CC2
V
CC2