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LT3032 Series

3032fd

APPLICATIONS INFORMATION

If wiring modiﬁcations are not permissible for the applica-

tions, including series resistance between the power supply

and the input of the LT3032 also stabilizes the application.

As little as 0.1Ω to 0.5Ω, often less, is effective in damp-

ing the LC resonance. If the added impedance between

the power supply and the input is unacceptable, adding

ESR to the input capacitor also provides the necessary

damping of the LC resonance. However, the required ESR

is generally higher than the series impedance required.

Thermal Considerations

The power handling capability of the device is limited by

the maximum rated junction temperature (125°C). The

power dissipated by the device is made up of the follow-

ing components:

1. Output current of each side multiplied by the respective

input/output voltage differential: (IOUT)(VIN to VOUT),

and

2. GND pin current for each side multiplied by its input

voltage: (IGND)(VIN)

The GND pin current of each side is found by examining

the GND Pin Current curves in the Typical Performance

Characteristics. Total power dissipation equals the sum

for both channels of the components listed above.

The LT3032 has internal thermal limiting designed to pro-

tect each side of the regulator during overload conditions.

For continuous normal conditions, the maximum junction

temperature rating of 125°C must not be exceeded. It is

important to give careful consideration to all sources of

thermal resistance from junction to ambient. Additional

heat sources mounted nearby must also be considered.

The LT3032 is a surface mount device and heat sinking is

accomplished by using the heat spreading capabilities of

the PC board and its copper traces. Copper board stiffen-

ers and plated through-holes can also be used to spread

the heat generated by power devices.

Note that the exposed pads (Pins 15 and 16) are elect-

rically connected to ground (GND) and the negative input

(INN) respectively.

The following table lists thermal resistance as a function

of copper area on a ﬁxed board size. All measurements

were taken in still air on a 4-layer FR-4 board with 1oz

solid internal planes and 2oz external trace planes with a

total ﬁnished board thickness of 1.6mm.

Table 3. DE Package, 14-Lead DFN

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

32°C/W

1000mm2

2500mm2

33°C/W

225mm2

2500mm2

38°C/W

100mm2

2500mm2

43°C/W

*Device is mounted on topside

For further information on thermal resistance and using

thermal information, refer to JEDEC standard JESD51,

notably JESD51-12.

PCB layers, copper weight, board layout and thermal vias

affect the resultant thermal resistance. This table provides

thermal resistance numbers for best-case 4-layer boards

with 1oz internal and 2oz external copper. Modern, mul-

tilayer PCBs may not be able to achieve quite the same

level performance as found in this table.

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