LT6301CFE#TR Linear Technology, LT6301CFE#TR Datasheet - Page 9

• Manufacturer Part Number: LT6301CFE#TR
• Description: IC XDSL LINE DRIVER DUAL 28TSSOP
• Manufacturer: Linear Technology
• Type: Driverr

Specifications of LT6301CFE#TR

• Number Of Drivers/receivers: 2/0
• Protocol: xDSL
• Voltage - Supply: 5 V ~ 12 V
• Mounting Type: Surface Mount
• Package / Case: 28-TSSOP Exposed Pad, 28-eTSSOP, 28-HTSSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LT6301CFETR

APPLICATIO S I FOR ATIO
These modes can be useful for overall system power
management when full power transmissions are not nec-
essary. Contact LTC Applications for single supply design
information.
Shutdown and Recovery
The ultimate power saving action on a completely idle port
is to fully shut down the line driver by pulling the SHDN pin
to within 0.4V of the SHDNREF potential. As shown in
Figure 5 complete shutdown occurs in less than 10 s and,
more importantly, complete recovery from the shut down
state to full operation occurs in less than 2 s. The biasing
circuitry in the LT6301 reacts very quickly to bring the
amplifiers back to normal operation.
SHDNREF = 0V
AMPLIFIER
OUTPUT
V
SHDN
Figure 5. Shutdown and Recovery Timing
1000pF
U
+IN
–IN
U
110
110
20mA DC
W
Figure 6. Estimating Line Driver Power Dissipation
–
+
+
–
A
B
1k
1k
–12V
12V
6301 F05
I
LOAD
SHDN
SHDNREF
24.9k – SETS I
–2V
U
2V
= 57mA
RMS
RMS
17.4
17.4
RMS
Q
PER AMPLIFIER = 10mA
1:1.7
6301 F06
Power Dissipation and Heat Management
xDSL applications require the line driver to dissipate a
significant amount of power and heat compared to other
components in the system. The large peak to RMS varia-
tions of DMT and CAP ADSL signals require high supply
voltages to prevent clipping, and the use of a step-up
transformer to couple the signal to the telephone line can
require high peak current levels. These requirements
result in the driver package having to dissipate significant
amounts of power. Several multiport cards inserted into
a rack in an enclosed central office box can add up to
many, many watts of power dissipation in an elevated
ambient temperature environment. The LT6301 has built-
in thermal shutdown circuitry that will protect the ampli-
fiers if operated at excessive temperatures, however data
transmissions will be seriously impaired. It is important in
the design of the PCB and card enclosure to take measures
to spread the heat developed in the driver away to the
ambient environment to prevent thermal shutdown (which
occurs when the junction temperature of the LT6301
exceeds 165 C).
Estimating Line Driver Power Dissipation
Figure 6 is a typical ADSL application shown for the
purpose of estimating the power dissipation in the line
driver. Due to the complex nature of the DMT signal,
100
3.16V
RMS
LT6301
sn6301 6301f
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