LT6300 UUWUAPPLICATIO S I FOR ATIO 45 VS = ±12V V+ = 12V 40 SHDN 35 V+ – 1.2V I ≈ S PER AMPLIFIER (mA) • 64 R 30 BIAS + 5k 25 R V+ – 1.2V BIAS = • 64 – 5k 20 IS PER AMPLIFIER (mA) PER AMPLIFIER (mA) SHDNREF 15 RBIAS I SUPPLY 10 5 0 4 7 10 30 50 70 90 100 130 150 170 190 210 230 250 270 290 RBIAS (kΩ) 6300 F03 Figure 3. RBIAS to Ground Current ControlTwo Control Inputs 12V OR VLOGIC RESISTOR VALUES (k Ω ) R R V SHDN SHDN TO VCC (12V)RSHDN TO VLOGIC LOGIC RC1 VLOGIC3V3.3V5V3V3.3V5V VC1 SHDN RSHDN 40.2 43.2 60.4 4.99 6.81 19.6 R 0V C0 V 2k R C0 C1 11.5 13.0 21.5 8.66 10.7 20.5 RCO 19.1 22.1 36.5 14.3 17.8 34.0 VVC1C0SUPPLY CURRENT PER AMPLIFIER (mA)HH 10 10 10 10 10 10 HL 7 7 7 7 7 7 SHDNREF LH 5 5 5 5 5 5 LL 2 2 2 2 2 2 One Control Input 12V OR VLOGIC RESISTOR VALUES (k Ω ) R R SHDN TO VCC (12V)RSHDN TO VLOGIC V SHDN LOGIC RC VLOGIC3V3.3V5V3V3.3V5V 0V VC SHDN RSHDN 40.2 43.2 60.4 4.99 6.81 19.6 R 2k C 7.32 8.25 13.7 5.49 6.65 12.7 VCSUPPLY CURRENT PER AMPLIFIER (mA)H 10 10 10 10 10 10 L 2 2 2 2 2 2 6300 F04 SHDNREF Figure 4. Providing Logic Input Control of Operating CurrentLogic Controlled Operating Current while maintaining less than 2Ω output impedance to frequencies less than 1MHz. This low power mode retains The DSP controller in a typical xDSL application can have termination impedance at the amplifier outputs and the I/O pins assigned to provide logic control of the LT6300 line driving back termination resistors. With this termina- line driver operating current. As shown in Figure 4 one or tion, while a DSL port is not transmitting data, it can still two logic control inputs can control two or four different sense a received signal from the line across the back- operating modes. The logic inputs add or subtract current termination resistors and respond accordingly. to the SHDN input to set the operating current. The one logic input example selects the supply current to be either The two logic input control provides two intermediate full power, 10mA per amplifier or just 2mA per amplifier, (approximately 7mA per amplifier and 5mA per amplifier) which significantly reduces the driver power consumption operating levels between full power and termination 8