IRF IRU1261 Dual 6a and 1a low dropout positive fixed 1.5v and 2.5v regulator Datasheet

Data Sheet No. PD94139
IRU1261
DUAL 6A AND 1A LOW DROPOUT
POSITIVE FIXED 1.5V AND 2.5V REGULATOR
DESCRIPTION
FEATURES
Guaranteed to Provide 1.5V and 2.5V Supplies
with 3.1V Input
Fast Transient Response
1% Voltage Reference Initial Accuracy
Built-In Thermal Shutdown
The IRU1261, using a proprietary process, combines a
dual low dropout regulator with fixed outputs of 1.5V and
2.5V in a single package with the 1.5V output having a
minimum of 6A and the 2.5V having a 1A output current
capability. This product is specifically designed to provide well regulated supplies from 3.3V to generate 1.5V
for GTL+ termination resistor supply and 2.5V clock
supply for the new generation of the Pentium IITM processor applications.
APPLICATIONS
Pentium IITM Processor Applications
TYPICAL APPLICATION
3.3V
C1
IRU1261
VOUT1
5
VIN
4
Gnd
3
VOUT2
2
VCTRL
1
2.5V / 1A
C3
C2
1.5V / 6A
C4
5V
R1
Figure 1 - Typical application of IRU1261 in a Pentium IITM processor application.
Note: Pentium IITM is trademark of Intel Corp.
PACKAGE ORDER INFORMATION
TJ (°C)
0 To 150
Rev. 2.0
09/19/02
5-PIN PLASTIC
TO-263 (M)
IRU1261CM
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5-PIN PLASTIC
Ultra Thin-PakTM (P)
IRU1261CP
1
IRU1261
ABSOLUTE MAXIMUM RATINGS
Input Voltage (V IN) ....................................................
Power Dissipation .....................................................
Storage Temperature Range ......................................
Operating Junction Temperature Range .....................
7V
Internally Limited
-65°C To 150°C
0°C To 150°C
PACKAGE INFORMATION
5-PIN ULTRA THIN-PAKTM (P)
5-PIN PLASTIC TO-263 (M)
5
VOUT1
5
V OUT1
4
VIN
4
V IN
3
Gnd
3
Gnd
2
VOUT2
2
V OUT2
1
VCTRL
1
V CTRL
θJA=308C/W for 1"sq pad
θJA=308C/W for 1"sq pad
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over CIN=1mF, COUT=100mF and TJ=0 to 1508C. Typical
values refer to TJ=258C. IFL=6A for output #2 and 1A for output #1. VCTRL=5V, VIN=3.3V.
PARAMETER
VCTRL Input Voltage
Output Voltage #2
SYM
Output Voltage #1
VO1
Line Regulation
Load Regulation (Note 1)
Dropout Voltage (Output #2)
Dropout Voltage (Output #1)
Current Limit (Output #2)
Current Limit (Output #1)
Minimum Load Current
Thermal Regulation
Ripple Rejection
Temperature Stability
Long Term Stability
RMS Output Noise
VO2
TEST CONDITION
Io=10mA, TJ=25°C
Io=10mA
Io=10mA, TJ=25°C
Io=10mA
Io=10mA, 3.1V<VIN<3.6V
10mA<Io<IFL
Note 2, Io=6A, VCTRL=4.75V
Note 2, Io=1A, VCTRL=4.75V
DVo=100mV
DVo=100mV
Note 3
30ms Pulse, Io=IFL
f=120Hz, Co=25mF Tantalum,
Io=0.5 3 IFL
Io=10mA
TJ=1258C, 1000Hrs
10Hz<f<10KHz
Note 1: Low duty cycle pulse testing with Kelvin connections is required in order to maintain accurate data.
Note 2: Dropout voltage is defined as the minimum differential voltage between VIN and VOUT required to maintain regulation at VOUT. It is measured when the output
voltage drops 1% below its nominal value.
2
MIN
3.0
1.485
1.470
2.462
2.425
TYP
MAX
1.500
1.500
2.500
2.500
0.2
0.4
1.515
1.530
2.537
2.575
0.4
1.3
0.6
5
0.01
10
0.02
6.1
1.1
70
0.5
0.3
0.003
UNITS
V
V
V
%
%
V
V
A
A
mA
%/W
dB
%
%
%VO
Note 3: Minimum load current is defined as the minimum current required at the output in order for the output voltage to maintain regulation. Typically the resistor
dividers are selected such that it automatically maintains this current.
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Rev. 2.0
09/19/02
IRU1261
PIN DESCRIPTIONS
PIN # PIN SYMBOL
PIN DESCRIPTION
1
VCTRL
The control input pin of the regulator. This pin is connected, via a 10V resistor, to the 5V
supply to provide the base current for the pass transistor of both regulators. This allows
the regulator to have very low dropout voltage which allows one to generate a well regulated 2.5V supply from the 3.3V input. A high frequency, 1mF capacitor is connected
between this pin and VIN pin to insure stability.
2
VOUT2
The output #2 (high current) of the regulator. A minimum of 100mF capacitor must be
connected from this pin to ground to insure stability.
3
Gnd
This pin is connected to ground. It is also the Tab of the package.
4
VIN
The power input pin of the regulator. Typically a large storage capacitor is connected from
this pin to ground to insure that the input voltage does not sag below the minimum drop
out voltage during the load transient response. This pin must always be higher than both
VOUT pins by the amount of the dropout voltage (see data sheet) in order for the device to
regulate properly.
5
VOUT1
The output #1 (low current) of the regulator. A minimum of 100mF capacitor must be
connected from this pin to ground to insure stability.
BLOCK DIAGRAM
VIN 4
5 VOUT1
V CTRL 1
THERMAL
SHUTDOWN
1.20V
+
3 Gnd
2 VOUT2
Figure 2 - Simplified block diagram of the IRU1261.
Rev. 2.0
09/19/02
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3
IRU1261
APPLICATION INFORMATION
Introduction
The IRU1261 is a dual fixed output Low Dropout (LDO)
regulator available in a TO-263 package. This voltage
regulator is designed specifically for Pentium II processor applications requiring 2.5V and 1.5V supplies, eliminating the need for a second regulator resulting in lower
overall system cost. The IRU1261 is designed to take
advantage of 5V supply to provide the drive for the pass
transistor, allowing 2.5V supply to be generated from
3.3V input. This feature improves the power dissipation
of the 2.5V regulator substantially allowing a smaller
heat sink to be used for the application. Compared to
the IRU1260 dual adjustable regulator, the IRU1261 includes the resistor dividers that are otherwise needed
with the IRU1260, eliminating four external components
and their tolerances, resulting in a more accurate initial
accuracy for each output voltage. Other features of the
device include: fast response to sudden load current
changes, such as GTL+ termination application and thermal shutdown protection to protect the device if an overload condition occurs.
Stability
The IRU1261 requires the use of an output capacitor as
part of the frequency compensation in order to make the
regulator stable. Typical designs for the microprocessor
applications use standard electrolytic capacitors with
typical ESR in the range of 50 to 100mV and the output
capacitance of 500 to 1000mF. Fortunately as the capacitance increases, the ESR decreases resulting in a
fixed RC time constant. The IRU1261 takes advantage
of this phenomena in making the overall regulator loop
stable. For most applications a minimum of 100mF aluminum electrolytic capacitor with the maximum ESR of
0.3V such as Sanyo, MVGX series, Panasonic FA series as well as the Nichicon PL series insures both stability and good transient response. The IRU1261 also
requires a 1mF ceramic capacitor connected from V IN to
VCTRL and a 10V, 0.1W resistor in series with VCTRL pin
in order to further insure stability.
Thermal Design
The IRU1261 incorporates an internal thermal shutdown
that protects the device when the junction temperature
exceeds the maximum allowable junction temperature.
Although this device can operate with junction temperatures in the range of 1508C, it is recommended that the
selected heat sink be chosen such that during maxi-
4
mum continuous load operation the junction temperature is kept below this number. The example given shows
the steps in selecting the proper regulator heat sink for
driving the Pentium II processor GTL+ termination resistors and the Clock IC using IRU1261 in TO-263 package.
Example:
Assuming the following specifications:
VIN = 3.3V
VOUT1 = 2.5V
VOUT2 = 1.5V
IOUT1(MAX) = 0.2A
IOUT2(MAX) = 1.5A
TA = 358C
The steps for selecting a proper heat sink to keep the
junction temperature below 1358C is given as:
1) Calculate the maximum power dissipation using:
PD = IOUT13(V IN - VOUT1) + IOUT23(V IN - VOUT2)
PD = 0.23(3.3 - 2.5) + 1.53(3.3 - 1.5) = 2.86W
2) Assuming a TO-263 surface mount package, the junction to ambient thermal resistance of the package is:
uJA = 308C/W for 1" square pad area
3) The maximum junction temperature of the device is
calculated using the equation below:
TJ = TA + PD3uJA
TJ = 35 + 2.86330 = 1218C
Since this is lower than our selected 1358C maximum junction temperature (1508C is the thermal shutdown of the device), TO-263 package is a suitable
package for our application.
Layout Consideration
The IRU1261 like all other high speed linear regulators
need to be properly laid out to insure stable operation.
The most important component is the output capacitor,
which needs to be placed close to the output pin and
connected to this pin using a plane connection with a
low inductance path.
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Rev. 2.0
09/19/02
IRU1261
TYPICAL APPLICATION
PENTIUM ΙΙ APPLICATION
3.3V
C1
IRU1261
VOUT1
5
VIN
4
Gnd
3
VOUT2
2
VCTRL
1
2.5V / 1A
C3
C2
1.5V / 6A
C4
5V
R1
Figure 3 - Typical application of IRU1261 in the Pentium IITM design with the 1.5V
output providing for GTL+ termination while 2.5V supplies the clock chip.
Note: Pentium IITM is trademark of Intel Corp.
Ref Desig
U1
C1, C4
C3
C2
R1
HS1
Description
Dual LDO Regulator
Capacitor
Capacitor
Capacitor
Resistor
Heat Sink
Qty
Part #
Manuf
1
IRU1261CM
IR
2
Elect, 680mF, EEUFA1A681L
Panasonic
1
Elect, 220mF, 6.3V, ECAOJFQ221 Panasonic
1
Ceramic, 1mF, 16V, Z5U
1
3V, 0.1W, 0805 SMT
Panasonic
1) Use 1" Square Copper Pad area if IOUT2<1.7A and
IOUT1<0.2A.
2) For IOUT2<3A and IOUT1<0.5A, use IRU1261CT and
Thermalloy 6030B
3) For IOUT2<5.4A and IOUT1<0.5A, use IRU1261CT and
Thermalloy 7021B
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
Rev. 2.0
09/19/02
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5
IRU1261
(M) TO-263 Package
5-Pin
A
E
U
K
S
V
B
M
H
L
P
G
D
N
C
R
C
L
SYMBOL MIN
MAX
A
10.05 10.668
B
8.28
9.169
C
4.31
4.597
D
0.66
0.91
E
1.14
1.40
G
1.575 1.829
H
14.605 15.875
K
1.143
1.68
L
0.00
0.305
M
2.49
2.74
N
0.33
0.58
P
2.286 2.794
R
08
88
S
1.143
2.67
U
6.50 REF
V
7.75 REF
NOTE: ALL MEASUREMENTS
ARE IN MILLIMETERS.
6
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Rev. 2.0
09/19/02
IRU1261
(P) Ultra Thin-PakTM
5-Pin
A
A1
E
U
K
V
B
H
M
L
P
G
D
N
C
R
C
L
SYMBOL
A
A1
B
C
D
E
G
H
K
L
M
N
P
R
U
V
MIN
MAX
9.27
9.52
8.89
9.14
7.87
8.13
1.78
2.03
0.63
0.79
0.25 NOM
1.72
10.41 10.67
0.76
1.27
0.03
0.13
0.89
1.14
0.25
0.79
1.04
38
68
5.59 NOM
7.49 NOM
NOTE: ALL MEASUREMENTS
ARE IN MILLIMETERS.
Rev. 2.0
09/19/02
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7
IRU1261
PACKAGE SHIPMENT METHOD
PKG
DESIG
M
P
PACKAGE
DESCRIPTION
TO-263
Ultra Thin-Pak
1
TM
1
PIN
COUNT
PARTS
PER TUBE
PARTS
PER REEL
T&R
Orientation
5
50
750
Fig A
5
75
2500
Fig B
1
1
Feed Direction
Figure A
8
1
1
Feed Direction
Figure B
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Rev. 2.0
09/19/02
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