IRU1010 查看數據表（PDF） - International Rectifier
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IRU1010 Datasheet PDF : 10 Pages
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IRU1010
Assuming the following specifications:
VIN = 5V
VF = 0.5V
VOUT = 2.85V
IOUT(MAX) = 0.8A
TA = 358C
To set the output DC voltage, we need to select R1 and
R2:
4) Assuming R1 = 121V, 1%:
( ) ( ) R2 =
VOUT
VREF
-1
3R1 =
2.85
1.25
-1
3121 = 154.8V
Where: VF is the forward voltage drop of the D1 diode as
shown in Figure 5.
Select R2 = 154V, 1%.
The steps for selecting the right package with proper
board area for heatsinking to keep the junction tempera-
ture below 1358C is given as:
D1
5V
C1
10uF
V IN
V OUT
IRU1010
2.85V
C2
22uF
1) Calculate the maximum power dissipation using:
PD = IOUT 3 (VIN - VF - VOUT)
PD = 0.8 3 (5 - 0.5 - 2.85) = 1.32W
2) Calculate the maximum θJA allowed for our example:
Adj
R1
121
1%
R2
154
1%
uJA(MAX) =
TJ - TA
PD
=
135 - 35
1.32
= 75.68C/W
Figure 5 - Final Schematic for half of the
GTL+ termination regulator.
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.
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. 1.7
02/03/03
IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105
TAC Fax: (310) 252-7903
Visit us at www.irf.com for sales contact information
Data and specifications subject to change without notice. 02/01
www.irf.com
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