BM1117 查看數據表（PDF） - Unspecified

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BM1117

Voltage Regulators

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SPECIFICATION

BM1117

Connected as shown above , RP is not

multiplied by the divider ratio

In the case of fixed voltage devices the top

of R1 is connected Kelvin internally, and

the ground pin can be used for negative

side sensing.

Thermal Considerations

The BM1117 series have internal power

and thermal limiting circuitry designed to

protect the device under overload

conditions. However maximum junction

temperature ratings of 125°C should not be

exceeded under continuous normal load

conditions.

Careful consideration must be given to all

sources of thermal resistance from junction

to ambient. For the surface mount package

SOT-223 additional heat sources mounted

near the device must be considered. The

heat dissipation capability of the PC board

and its copper traces is used as a heat sink

for the device. The thermal resistance from

the junction to the tab for the BM1117 is

15°C/W. Thermal resistance from tab to

ambient can be as low as 30°C/W.

The total thermal resistance from junction

to ambient can be as low as 45°C/W. This

requires a reasonable sized PC board with

at least on layer of copper to spread the

heat across the board and couple it into the

surrounding air.

Experiments have shown that the heat

spreading copper layer does not need to be

electrically connected to the tab of the device.

The PC material can be very effective at

transmitting heat between the pad area,

attached to the pad of the device, and a

ground plane layer either inside or on the

opposite side of the board. Although the

actual thermal resistance of the PC material

is high, the Length/Area ratio of the thermal

resistance between layers is small. The data

in Table 1, was taken using1/16” FR-4 board

with 1 oz. copper foil, and it can be used as a

rough guideline for estimating thermal

resistance.

For each application the thermal resistance

will be affected by thermal interactions with

other components on the board. To

determine the actual value some

experimentation will be necessary.

The power dissipation of the BM1117 is equal

to:

PD = ( VIN - VOUT )( IOUT )

Maximum junction temperature will be equal

to:

TJ = TA(MAX) + PD

PD :Thermal esistance (junction-to-ambient)

Maximum junction temperature must not

exceed 125°C.

Table 1.

COPPER AREA

TOP SIDE*

BACK SIDE

2500 Sq. mm

2500 Sq. mm

1000 Sq. mm

2500 Sq. mm

225 Sq. mm

2500 Sq. mm

100 Sq. mm

2500 Sq. mm

1000 Sq. mm

1000 Sq. mm

1000 Sq. mm

0

BOARD AREA

2500 Sq. mm

2500 Sq. mm

2500 Sq. mm

2500 Sq. mm

1000 Sq. mm

1000 Sq. mm

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

45°C/W

45°C/W

53°C/W

59°C/W

52°C/W

55°C/W

BOOKLY MICRO ELECTRONICS LIMITED CORP.

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