Datasheet LT3010, LT3010-5 (Analog Devices) - 10

LT3010/LT3010-5
APPLICATIONS INFORMATION
20
Thermal Considerations
BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF 0 The power handling capability of the device will be lim- X5R ited by the maximum rated junction temperature (125°C, –20 LT3010E/LT3010MP or 140°C, LT3010H). The power dissi- –40 pated by the device will be made up of two components: 1. Output current multiplied by the input/output voltage –60 CHANGE IN VALUE (%) Y5V differential: IOUT • (VIN – VOUT) and, –80 2. GND pin current multiplied by the input voltage: –100 IGND • VIN 0 2 4 6 8 10 12 14 16 DC BIAS VOLTAGE (V) 30105 F03 The GND pin current can be found by examining the GND Pin Current curves in the Typical Performance Character-
Figure 3. Ceramic Capacitor DC Bias Characteristics
istics. Power dissipation will be equal to the sum of the two components listed above. 40 The LT3010 series regulators have internal thermal limiting 20 designed to protect the device during overload conditions. 0 For continuous normal conditions the maximum junction X5R temperature rating of 125°C (LT3010E/LT3010MP) or –20 140°C (LT3010H) must not be exceeded. It is important –40 Y5V to give careful consideration to all sources of thermal re- –60 CHANGE IN VALUE (%) sistance from junction to ambient. Additional heat sources mounted nearby must also be considered. –80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10µF For surface mount devices, heat sinking is accomplished –100–50 –25 0 25 50 75 100 125 by using the heat spreading capabilities of the PC board TEMPERATURE (°C) 30105 F04 and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the heat gener-
Figure 4. Ceramic Capacitor Temperature Characteristics
ated by power devices. capacitance change over temperature. Capacitance change The following table lists thermal resistance for several due to DC bias with X5R and X7R capacitors is better than different board sizes and copper areas. All measurements Y5V and Z5U capacitors, but can still be significant enough were taken in still air on 3/32" FR-4 board with one ounce to drop capacitor values below appropriate levels. Capaci- copper. tor DC bias characteristics tend to improve as component case size increases, but expected capacitance at operating
Table 1. Measured Thermal Resistance
voltage should be verified.
COPPER AREA THERMAL RESISTANCE
Voltage and temperature coefficients are not the only
TOPSIDE BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
sources of problems. Some ceramic capacitors have a 2500 sq mm 2500 sq mm 2500 sq mm 40°C/W piezoelectric response. A piezoelectric device generates 1000 sq mm 2500 sq mm 2500 sq mm 45°C/W voltage across its terminals due to mechanical stress, simi- 225 sq mm 2500 sq mm 2500 sq mm 50°C/W lar to the way a piezoelectric accelerometer or microphone 100 sq mm 2500 sq mm 2500 sq mm 62°C/W works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. 30105fe 10 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Applications Information Typical Applications Package Description Revision History Typical Application Related Parts