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LT3010

50mA, 3V to 80V Low Dropout Micropower Linear Regulator

Linear Technology 

LT3010/LT3010-5

APPLICATIONS INFORMATION

20

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

0

X5R

–20

–40

–60

Y5V

–80

–100

0 2 4 6 8 10 12 14 16

DC BIAS VOLTAGE (V)

30105 F03

Figure 3. Ceramic Capacitor DC Bias Characteristics

40

20

0

X5R

–20

–40

Y5V

–60

–80

BOTH CAPACITORS ARE 16V,

–100 1210 CASE SIZE, 10µF

–50 –25 0 25 50 75

TEMPERATURE (°C)

100 125

30105 F04

Figure 4. Ceramic Capacitor Temperature Characteristics

capacitance change over temperature. Capacitance change

due to DC bias with X5R and X7R capacitors is better than

Y5V and Z5U capacitors, but can still be significant enough

to drop capacitor values below appropriate levels. Capaci-

tor DC bias characteristics tend to improve as component

case size increases, but expected capacitance at operating

voltage should be verified.

Voltage and temperature coefficients are not the only

sources of problems. Some ceramic capacitors have a

piezoelectric response. A piezoelectric device generates

voltage across its terminals due to mechanical stress, simi-

lar to the way a piezoelectric accelerometer or microphone

works. For a ceramic capacitor the stress can be induced

by vibrations in the system or thermal transients.

Thermal Considerations

The power handling capability of the device will be lim-

ited by the maximum rated junction temperature (125°C,

LT3010E/LT3010MP or 140°C, LT3010H). The power dissi-

pated by the device will be made up of two components:

1. Output current multiplied by the input/output voltage

differential: IOUT • (VIN – VOUT) and,

2. GND pin current multiplied by the input voltage:

IGND • VIN

The GND pin current can be found by examining the GND

Pin Current curves in the Typical Performance Character-

istics. Power dissipation will be equal to the sum of the

two components listed above.

The LT3010 series regulators have internal thermal limiting

designed to protect the device during overload conditions.

For continuous normal conditions the maximum junction

temperature rating of 125°C (LT3010E/LT3010MP) or

140°C (LT3010H) must not be exceeded. It is important

to give careful consideration to all sources of thermal re-

sistance from junction to ambient. Additional heat sources

mounted nearby must also be considered.

For surface mount devices, heat sinking is accomplished

by using the heat spreading capabilities of the PC board

and its copper traces. Copper board stiffeners and plated

through-holes can also be used to spread the heat gener-

ated by power devices.

The following table lists thermal resistance for several

different board sizes and copper areas. All measurements

were taken in still air on 3/32" FR-4 board with one ounce

copper.

Table 1. Measured Thermal Resistance

COPPER AREA

THERMAL RESISTANCE

TOPSIDE BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)

2500 sq mm 2500 sq mm 2500 sq mm

40°C/W

1000 sq mm 2500 sq mm 2500 sq mm

45°C/W

225 sq mm 2500 sq mm 2500 sq mm

50°C/W

100 sq mm 2500 sq mm 2500 sq mm

62°C/W

30105fe

10

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