IRU1010(2001) 查看數據表（PDF） - International Rectifier

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IRU1010
(Rev.:2001)

1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR

International Rectifier 

IRU1010

ing the proper regulator in a surface-mount package. To set the output DC voltage, we need to select R1 and

(See IRU1015 for non-surface-mount packages)

R2:

Assuming the following specifications:

VIN = 5V

VF = 0.5V

Vo = 2.85V

IOUT(MAX) = 0.8A

TA = 35!C

Where: VF is the forward voltage drop of the D1diode as

shown in Figure 5.

The steps for selecting the right package with proper

board area for heatsinking to keep the junction tempera-

ture below 135!C is given as:

1) Calculate the maximum power dissipation using:

PD = IOUT × (VIN - VF - VOUT)

PD = 0.8 × (5 - 0.5 - 2.85) = 1.32W

2) Calculate the maximum θJA allowed for our example:

θJA(MAX) =

TJ - TA

PD

=

135 - 35

1.32

= 75.6!C/W

3) Select a package from the datasheet with lower θJA

than the one calculated in the previous step.

Selecting TO-252 (D-Pak) with at least 0.5" square

of 0.062" FR4 board using 1 oz. copper has 70°C/W

which is lower than the calculated number.

4) Assuming R1 = 121Ω, 1%

R2 =oVVOREUFT -1p× R1 =o21..8255 - 1p× 121 = 154.8Ω

Select R2 = 154Ω, 1%

D1

5V

C1

10uF

Vin

Vout

IRU1010

Adj

2.85V

C2

22uF

R1

121

1%

R2

154

1%

1010app4-1.3

Figure 5 - Final Schematic for half of the

GTL+ termination regulator

Layout Consideration

The output capacitors must be located as close to the

Vout terminal of the device as possible. It is recom-

mended to use a section of a layer of the PC board as a

plane to connect the Vout pin to the output capacitors to

prevent any high frequency oscillation that may result

due to excessive trace inductance.

Rev. 1.4

06/29/01

5

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