Electronic Components Datasheet Search |
|
LT1739 Datasheet(PDF) 10 Page - Linear Technology |
|
LT1739 Datasheet(HTML) 10 Page - Linear Technology |
10 / 16 page 10 LT6301 sn6301 6301f which looks very much like noise, it is easiest to use the RMS values of voltages and currents for estimating the driver power dissipation. The voltage and current levels shown for this example are for a full-rate ADSL signal driving 20dBm or 100mWRMS of power on to the 100Ω telephone line and assuming a 0.5dBm insertion loss in the transformer. The quiescent current for the LT6301 is set to 10mA per amplifier. The power dissipated in the LT6301 is a combination of the quiescent power and the output stage power when driving a signal. The two pairs of amplifiers are configured to place a differential signal on two lines. The Class AB output stage in each amplifier will simultaneously dissipate power in the upper power transistor of one amplifier, while sourc- ing current, and the lower power transistor of the other amplifier, while sinking current. The total device power dissipation is then: PD = PQUIESCENT + PQ(UPPER) + PQ(LOWER) PD = (V+ – V–) • IQ + (V+ – VOUTARMS) • ILOAD + (V – – VOUTBRMS) • ILOAD With no signal being placed on the line and the amplifier biased for 10mA per amplifier supply current, the quies- cent driver power dissipation is: PDQ = [24V • 10mA] • 4 = 960mW This can be reduced in many applications by operating with a lower quiescent current value or shutting down the part during idle conditions. When driving a load, a large percentage of the amplifier quiescent current is diverted to the output stage and becomes part of the load current. Figure 7 illustrates the total amount of biasing current flowing between the + and – power supplies through the amplifiers as a function of load current for one differential driver. As much as 60% of the quiescent no load operating current is diverted to the load. At full power to both lines the total package power dissi- pation is: PD(FULL) = [24V • 8mA + (12V – 2VRMS) • 57mARMS + [|–12V – (– 2VRMS)|] • 57mARMS] • 2 PD(FULL) = [192mW + 570mW + 570mW] • 2 = 2.664W* The junction temperature of the driver must be kept less than the thermal shutdown temperature when processing a signal. The junction temperature is determined from the following expression: TJ = TAMBIENT (°C) + PD(FULL) (W) • θJA (°C/W) θJA is the thermal resistance from the junction of the LT6301 to the ambient air, which can be minimized by heat-spreading PCB metal and airflow through the enclo- sure as required. For the example given, assuming a maximum ambient temperature of 50 °C and keeping the junction temperature of the LT6301 to 150 °C maximum, the maximum thermal resistance from junction to ambient required is: θJA MAX CC W CW () – . ./ = °° =° 150 50 2 664 37 5 APPLICATIO S I FOR ATIO Figure 7. IQ vs ILOAD ILOAD (mA) (ONE DIFFERENTIAL DRIVER) –240 –200 –160 –120 –80 –40 0 40 80 120 160 200 240 10 15 20 6301 F07 5 0 25 *Design techniques exist to significantly reduce this value (See Line Driving Back Termination). |
Similar Part No. - LT1739 |
|
Similar Description - LT1739 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |