IRU1010 International Rectifier, IRU1010 Datasheet - Page 5

• Manufacturer Part Number: IRU1010
• Description: 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR
• Manufacturer: International Rectifier

ing the proper regulator in a surface-mount package.
(See IRU1015 for non-surface-mount packages)
Assuming the following specifications:
Where: V
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:
2) Calculate the maximum
3) Select a package from the datasheet with lower
Rev. 1.4
06/29/01
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.
V
V
Vo = 2.85V
I
T
P
P
θ
OUT(MAX)
JA(MAX)
A
IN
F
D
D
= 35!C
= 0.5V
= 0.8 × (5 - 0.5 - 2.85) = 1.32W
= I
= 5V
F
OUT
is the forward voltage drop of the D1diode as
=
= 0.8A
× (V
T
J
P
- T
D
IN
A
- V
=
135 - 35
F
- V
1.32
JA
OUT
allowed for our example:
)
= 75.6!C/W
JA
To set the output DC voltage, we need to select R1 and
R2:
4) Assuming R1 = 121Ω, 1%
Select R2 = 154Ω, 1%
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.
5V
R
2
10uF
=o o o o o
Figure 5 - Final Schematic for half of the
C1
D1
V
V
OUT
REF
GTL+ termination regulator
-1p p p p p × R
Vin
IRU1010
Adj
1
=o o o o o
2.85
1.25
Vout
- 1p p p p p × 121 = 154.8Ω
R1
121
1%
R2
154
1%
IRU1010
1010app4-1.3
C2
22uF
2.85V
5