Datasheet LT6301 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | Dual 500mA, Differential xDSL Line Driver in 28-Lead TSSOP Package |
| Pages / Page | 16 / 9 — APPLICATIO S I FOR ATIO. Power Dissipation and Heat Management. Shutdown … |
| File Format / Size | PDF / 252 Kb |
| Document Language | English |
APPLICATIO S I FOR ATIO. Power Dissipation and Heat Management. Shutdown and Recovery
Model Line for this Datasheet
Text Version of Document
LT6301
U U W U APPLICATIO S I FOR ATIO
These modes can be useful for overall system power
Power Dissipation and Heat Management
management when full power transmissions are not nec- xDSL applications require the line driver to dissipate a essary. Contact LTC Applications for single supply design significant amount of power and heat compared to other information. components in the system. The large peak to RMS varia- tions of DMT and CAP ADSL signals require high supply
Shutdown and Recovery
voltages to prevent clipping, and the use of a step-up The ultimate power saving action on a completely idle port transformer to couple the signal to the telephone line can is to fully shut down the line driver by pulling the SHDN pin require high peak current levels. These requirements to within 0.4V of the SHDNREF potential. As shown in result in the driver package having to dissipate significant Figure 5 complete shutdown occurs in less than 10µs and, amounts of power. Several multiport cards inserted into more importantly, complete recovery from the shut down a rack in an enclosed central office box can add up to state to full operation occurs in less than 2µs. The biasing many, many watts of power dissipation in an elevated circuitry in the LT6301 reacts very quickly to bring the ambient temperature environment. The LT6301 has built- amplifiers back to normal operation. 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 VSHDN SHDNREF = 0V 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 AMPLIFIER OUTPUT exceeds 165°C).
Estimating Line Driver Power Dissipation
6301 F05 Figure 6 is a typical ADSL application shown for the
Figure 5. Shutdown and Recovery Timing
purpose of estimating the power dissipation in the line driver. Due to the complex nature of the DMT signal, 12V 20mA DC 24.9k – SETS IQ PER AMPLIFIER = 10mA 2V +IN + RMS SHDN 17.4Ω A – 1k 1:1.7 110Ω • • ILOAD = 57mARMS 100Ω 3.16VRMS 1000pF 110Ω 1k – 17.4Ω 6301 F06 B SHDNREF –IN + –12V –2VRMS
Figure 6. Estimating Line Driver Power Dissipation
sn6301 6301f 9
U U W U APPLICATIO S I FOR ATIO
These modes can be useful for overall system power
Power Dissipation and Heat Management
management when full power transmissions are not nec- xDSL applications require the line driver to dissipate a essary. Contact LTC Applications for single supply design significant amount of power and heat compared to other information. components in the system. The large peak to RMS varia- tions of DMT and CAP ADSL signals require high supply
Shutdown and Recovery
voltages to prevent clipping, and the use of a step-up The ultimate power saving action on a completely idle port transformer to couple the signal to the telephone line can is to fully shut down the line driver by pulling the SHDN pin require high peak current levels. These requirements to within 0.4V of the SHDNREF potential. As shown in result in the driver package having to dissipate significant Figure 5 complete shutdown occurs in less than 10µs and, amounts of power. Several multiport cards inserted into more importantly, complete recovery from the shut down a rack in an enclosed central office box can add up to state to full operation occurs in less than 2µs. The biasing many, many watts of power dissipation in an elevated circuitry in the LT6301 reacts very quickly to bring the ambient temperature environment. The LT6301 has built- amplifiers back to normal operation. 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 VSHDN SHDNREF = 0V 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 AMPLIFIER OUTPUT exceeds 165°C).
Estimating Line Driver Power Dissipation
6301 F05 Figure 6 is a typical ADSL application shown for the
Figure 5. Shutdown and Recovery Timing
purpose of estimating the power dissipation in the line driver. Due to the complex nature of the DMT signal, 12V 20mA DC 24.9k – SETS IQ PER AMPLIFIER = 10mA 2V +IN + RMS SHDN 17.4Ω A – 1k 1:1.7 110Ω • • ILOAD = 57mARMS 100Ω 3.16VRMS 1000pF 110Ω 1k – 17.4Ω 6301 F06 B SHDNREF –IN + –12V –2VRMS
Figure 6. Estimating Line Driver Power Dissipation
sn6301 6301f 9
