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CS5204-3GT3 Datasheet(PDF) 7 Page - ON Semiconductor |
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CS5204-3GT3 Datasheet(HTML) 7 Page - ON Semiconductor |
7 / 10 page CS5204−1, CS5204−3, CS5204−5 http://onsemi.com 7 Calculating Power Dissipation and Heat Sink Requirements The CS5204−x series of linear regulators includes thermal shutdown and current limit circuitry to protect the device. High power regulators such as these usually operate at high junction temperatures so it is important to calculate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is used. The case is connected to VOUT on the CS5204−x, electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators such as these. The thermal characteristics of an IC depend on the following four factors: 1. Maximum Ambient Temperature TA (°C) 2. Power dissipation PD (Watts) 3. Maximum junction temperature TJ (°C) 4. Thermal resistance junction to ambient RqJA (°C/W) These four are related by the equation TJ + TA ) PD R QJA (1) The maximum ambient temperature and the power dissipation are determined by the design while the maximum junction temperature and the thermal resistance depend on the manufacturer and the package type. The maximum power dissipation for a regulator is: PD(max) + {VIN(max) * VOUT(min)}IOUT(max) ) VIN(max)IQ (2) where: VIN(max) is the maximum input voltage, VOUT(min) is the minimum output voltage, IOUT(max) is the maximum output current, for the application IQ is the maximum quiescent current at IOUT(max). A heat sink effectively increases the surface area of the package to improve the flow of heat away from the IC and into the surrounding air. Each material in the heat flow path between the IC and the outside environment has a thermal resistance. Like series electrical resistances, these resistances are summed to determine RqJA, the total thermal resistance between the junction and the surrounding air. 1. Thermal Resistance of the junction to case, RqJC ( °C/W) 2. Thermal Resistance of the case to Heat Sink, RqCS ( °C/W) 3. Thermal Resistance of the Heat Sink to the ambient air, RqSA (°C/W) These are connected by the equation: R QJA + RQJC ) RQCS ) RQSA (3) The value for RqJA is calculated using equation (3) and the result can be substituted in equation (1). The value for RqJC is 3.5°C/W for a given package type based on an average die size. For a high current regulator such as the CS5204−x the majority of the heat is generated in the power transistor section. The value for RqSA depends on the heat sink type, while RqCS depends on factors such as package type, heat sink interface (is an insulator and thermal grease used?), and the contact area between the heat sink and the package. Once these calculations are complete, the maximum permissible value of RqJA can be calculated and the proper heat sink selected. For further discussion on heat sink selection, see application note “Thermal Management,” document number AND8036/D, available through the Literature Distribution Center or via our website at http://onsemi.com. ORDERING INFORMATION Orderable Part Number Type Package Shipping† CS5204−1GT3 4.0 A, Adj. Output TO−220−3, STRAIGHT 50 Units / Rail CS5204−1GDP3 4.0 A, Adj. Output D2PAK−3 50 Units / Rail CS5204−1GDPR3 4.0 A, Adj. Output D2PAK−3 750 / Tape & Reel CS5204−3GT3 4.0 A, 3.3 V Output TO−220−3, STRAIGHT 50 Units / Rail CS5204−3GDP3 4.0 A, 3.3 V Output D2PAK−3 50 Units / Rail CS5204−3GDPR3 4.0 A, 3.3 V Output D2PAK−3 750 / Tape & Reel CS5204−5GT3 4.0 A, 5.0 V Output TO−220−3, STRAIGHT 50 Units / Rail †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. |
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Similar Description - CS5204-3GT3 |
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