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PDF IRU1117 Data sheet ( Hoja de datos )
| Número de pieza | IRU1117 | |
| Descripción | 800mA LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR | |
| Fabricantes | International Rectifier | |
| Logotipo |  |
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Data Sheet No. PD94136
IRU1117
800mA LOW DROPOUT POSITIVE
ADJUSTABLE REGULATOR
FEATURES
Guaranteed < 1.2V Dropout at 800mA Load
Current
Fast Transient Response
1% Voltage Reference Initial Accuracy
Built-In Thermal Shutdown
Available in SOT-223, D-Pak, Ultra Thin-PakTM
and 8-Pin SOIC Surface-Mount Packages
APPLICATIONS
VGA & Sound Card Applications
Low Voltage High Speed Termination Applications
Standard 3.3V Chip Set and Logic Applications
DESCRIPTION
The IRU1117 is a low dropout, three-terminal adjustable
regulator with minimum of 800mA output current capa-
bility. This product is specifically designed to provide
well regulated supply for low voltage IC applications such
as high speed bus termination and low current 3.3V logic
supply. The IRU1117 is also well suited for other applica-
tions such as VGA and sound cards. The IRU1117 is
guaranteed to have <1.2V dropout at full load current
making it ideal to provide well regulated outputs of 2.5V
to 3.6V with 4.75V to 7V input supply.
TYPICAL APPLICATION
D1
5V
C1
10uF
3VI N
IRU1117
2VO U T
Adj 1
2.85V / 800mA
R1
121
C2
R2 10uF
154
Figure 1 - Typical application of IRU1117 in a 5V to 2.85V SCSI termination regulator.
PACKAGE ORDER INFORMATION
TJ (°C)
0 To 150
2-PIN PLASTIC
TO-252 (D-Pak)
IRU1117CD
2-PIN PLASTIC
Ultra Thin-PakTM (P)
IRU1117CP
8-PIN PLASTIC
SOIC (S)
IRU1117CS
3-PIN PLASTIC
SOT-223 (Y)
IRU1117CY
Rev. 1.8
02/04/03
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IRU1117
Assuming the following specifications:
VIN = 5V
VF = 0.5V
VOUT = 2.85V
IOUT(MAX) = 0.8A
TA = 358C
Where:
VF is the forward voltage drop of the D1 diode as
shown in Figure 5.
+5V is significantly more than required to maintain drop-
out voltage across the IRU1117 when regulating VOUT to
2.85V. The "Extra" voltage means additional power is
dissapated in the IRU1117. The diode dissapates some
of this additional power, allowing the IRU1117 to run cooler.
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
1.25
3121 = 154.8V
Select R2 = 154V, 1%
5) Calculate the power dissapation for the schottky di-
ode (D1):
PD = VF 3 IOUT
PD = 0.5 3 0.8 = 0.4W
and select a suitable component.
The steps for selecting the right package with proper
board area for heat sinking to keep the junction tem-
perature below 1358C is given as:
D1
5V
C1
10uF
VIN VOUT
IRU1117
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
Adj R1
121
1%
R2
154
1%
2) Calculate the maximum uJA allowed for our ex-
ample:
uJA(MAX)
= TJ - TA
PD
=
135 - 35
1.32
=
75.68C/W
3) Select a package from the data sheet with lower uJA
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 1oz. copper has 70°C/W
which is lower than the calculated number.
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. 1.8
02/04/03
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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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| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet IRU1117.PDF ] | |
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