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## LME49600_14 Datasheet(数据表) 16 Page - Texas Instruments

 部件型号 LME49600 说明 High Performance, High Fidelity, High Current Audio Buffer 下载 22 Pages Scroll/Zoom 100% 制造商 TI1 [Texas Instruments] 网页 http://www.ti.com 标志 ## LME49600 Datasheet(HTML) 16 Page - Texas Instruments           16 page LME49600SNAS422D – JANUARY 2008 – REVISED MARCH 2008www.ti.comNOTEThe allowable thermal resistance is determined by the maximum allowable temperatureincrease:TRISE = TJ(MAX) - TA(MAX)Thus, if ambient temperature extremes force TRISE to exceed the design maximum, the part must be de-rated byeither decreasing PD to a safe level, reducing θJA further or, if available, using a larger copper area.Procedure1. First determine the maximum power dissipated by the LME49600, PD(MAX). For the simple case of the bufferdriving a resistive load, and assuming equal supplies, PD(MAX) is given by:PDMAX(AC) = (IS x VS) + (VS)2 / (2π2RL) (Watts)(2)PDMAX(DC) = (IS x VS) + (VS)2 / RL (Watts)where•VS = |VEE| + VCC (V)•IS =quiescent supply current (A)(3)Equation (2) is for sinusoidal output voltages and Equation (3) is for DC output voltages.2. Determine the maximum allowable die temperature rise,TRISE(MAX) = TJ(MAX) - TA(MAX) (°C)(4)3. Using the calculated value of TRISE(MAX) and PD(MAX), find the required value of junction to ambient thermalresistance combining Equation (1) and Equation (5) to derive Equation (9):θJA = TRISE(MAX) / PD(MAX)(5)4. Finally, choose the minimum value of copper area from Figure 30 based on the value forθJA.ExampleAssume the following conditions: VS = |VEE| + VCC = 30V, RL = 32Ω, IS = 15mA, sinusoidal output voltage, TJ(MAX)= 125°C, TA(MAX) = 85°C.Applying Equation (3):PDMAX = (IS x VS) + (VS)2 / 2π2RL= (15mA)(30V) + 900V2 / 142Ω= 1.86W(6)Applying Equation (5):TRISE(MAX) = 125°C – 85°C= 40°C(7)Applying Equation (9):θJA = 40°C/1.86W= 21.5°C/W(8)Examining the Copper Area vs.θJA plot indicates that a thermal resistance of 50°C/W is possible with a 12in2plane of one layer of 1oz copper. Other solutions include using two layers of 1oz copper or the use of 2ozcopper. Higher dissipation may require forced air flow. As a safety margin, an extra 15% heat sinking capability isrecommended.When amplifying AC signals, wave shapes and the nature of the load (reactive, non-reactive) also influencedissipation. Peak dissipation can be several times the average with reactive loads. It is particularly important todetermine dissipation when driving large load capacitance.The LME49600’s dissipation in DC circuit applications is easily computed using Equation (4). After the value ofdissipation is determined, the heat sink copper area calculation is the same as for AC signals.16Submit Documentation FeedbackCopyright © 2008, Texas Instruments IncorporatedProduct Folder Links: LME49600

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