Electronic Components Datasheet Search |
|
LT1497 Datasheet(PDF) 9 Page - Linear Technology |
|
LT1497 Datasheet(HTML) 9 Page - Linear Technology |
9 / 12 page 9 LT1497 or power plane layer either inside or on the opposite side of the board. Copper board stiffeners and plated through- holes can also be used to spread the heat generated by the device. Table 1 lists the thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with 2oz copper. This data can be used as a rough guideline in estimating thermal resistance. The thermal resistance for each appli- cation will be affected by thermal interactions with other components as well as board size and shape. Table 1. Fused 16-lead and 8-lead SO Packages TOTAL θJA θJA TOPSIDE BACKSIDE COPPER AREA (16-LEAD) (8-LEAD) 2500mm2 2500mm2 5000mm2 40 °C/W 80 °C/W 1000mm2 2500mm2 3500mm2 46 °C/W 92 °C/W 600mm2 2500mm2 3100mm2 48 °C/W 96 °C/W 180mm2 2500mm2 2680mm2 49 °C/W 98 °C/W 180mm2 1000mm2 1180mm2 56 °C/W 112 °C/W 180mm2 600mm2 780mm2 58 °C/W 116 °C/W 180mm2 300mm2 480mm2 59 °C/W 118 °C/W 180mm2 100mm2 280mm2 60 °C/W 120 °C/W 180mm2 0mm2 180mm2 61 °C/W 122 °C/W Calculating Junction Temperature The junction temperature can be calculated from the equation: TJ = (PD)(θJA) + TA TJ = Junction Temperature TA = Ambient Temperature PD = Power Dissipation θJA = Thermal Resistance (Junction-to-Ambient) As an example, calculate the junction temperature for the circuit in Figure 1 assuming an 85 °Cambienttemperature. The device dissipation can be found by measuring the supply currents, calculating the total dissipation and then subtracting the dissipation in the load and feedback net- work. Both amplifiers are in a gain of –1. The dissipation for each amplifier is: PD = (1/2)(86.4mA)(30V) – (10V)2/(200||560) = 0.62W The total dissipation is 1.24W. When a 2500mm2 PC board with 2oz copper on top and bottom is used, the thermal resistance is 40 °C/W. The junction temperature TJ is: TJ = (1.24W)(40°C/W) + 85°C = 135°C The maximum junction temperature for the LT1497 is 150 °C, so the heat sinking capability of the board is adequate for the application. If the copper area on the PC board is reduced to 180mm2 the thermal resistance increases to 61 °C/W and the junc- tion temperature becomes: TJ = (1.24W)(61°C/W) + 85°C = 161°C which is above the maximum junction temperature indi- cating that the heat sinking capability of the board is inadequate and should be increased. APPLICATIONS INFORMATION COPPER AREA (2oz) 560 Ω – 15V 560 Ω 560 Ω 560 Ω 86.4mA 15V 200 Ω 200 Ω 1497 F01 A –10V 10V f = 2MHz Figure 1. Thermal Calculation Example Slew Rate Unlike a traditional op amp, the slew rate of a current feedback amplifier is not independent of the amplifier gain configuration. There are slew rate limitations in both the input stage and the output stage. In the inverting mode and for higher gains in the noninverting mode, the signal amplitude on the input pins is small and the overall slew rate is that of the output stage. The input stage slew rate is related to the quiescent current in the input devices. Referring to the Simplified Schematic, for noninverting applications the two current sources in the input stage slew the parasitic internal capacitances at the bases of Q3 and Q4. Consider a positive going input at the base of Q1 and Q2. If the input slew rate exceeds the internal slew rate, |
Similar Part No. - LT1497 |
|
Similar Description - LT1497 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | 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 |