View IRU1117CS_277544.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Data Sheet No. PD94136
IRU1117
800mA LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR DESCRIPTION
The IRU1117 is a low dropout, three-terminal adjustable regulator with minimum of 800mA output current capability. 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 applications 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.
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-Pak TM 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
TYPICAL APPLICATION
D1
5V
C1 10uF VIN
3 2
R1 121
IRU1117
VOUT
2.85V / 800mA
C2 10uF
Adj
1
R2 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
www.irf.com
1
IRU1117
ABSOLUTE MAXIMUM RATINGS
Input Voltage (VIN) .................................................... Power Dissipation ..................................................... Storage Temperature Range ...................................... Operating Junction Temperature Range ..................... 7V Internally Limited -65C To 150C 0C To 150C
PACKAGE INFORMATION
2-PIN PLASTIC TO-252 (D-Pak)
FRONT VIEW 3
2-PIN ULTRA THIN-PAKTM (P)
FRONT VIEW
8-PIN PLASTIC SOIC (S)
TOP VIEW
3-PIN PLASTIC SOT-223 (Y)
TOP VIEW
VIN Tab is VOUT
3
VIN VIN
1 2 3 4
8 7 6 5
VOUT VOUT VOUT VOUT Tab is VOUT
3 2 1
Tab is VOUT
1
VIN VOUT Adj
NC NC
1
Adj
Adj
Adj
JA=70C/W for 0.5" Sq pad
JA=70C/W for 0.5" Sq pad
JA=55C/W for 1" Sq pad
JA=90C/W for 0.4" Sq pad
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over CIN=1mF, COUT=10mF, and TJ=0 to 1508C. Typical values refer to TJ=258C. PARAMETER Reference Voltage Line Regulation Load Regulation (Note 1) Dropout Voltage (Note 2) Current Limit Minimum Load Current (Note 3) Thermal Regulation Ripple Rejection Adjust Pin Current Adjust Pin Current Change Temperature Stability Long Term Stability RMS Output Noise IADJ SYM VREF TEST CONDITION Io=10mA, TJ=258C, (VIN-Vo)=1.5V Io=10mA, (VIN-Vo)=1.5V Io=10mA, 1.3V<(VIN-Vo)<7V VIN=3.3V, VADJ=0, 10mADVO
1.2 1.1 1.1 5 0.01 60 70 55 0.2 0.5 0.3 0.003
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.
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. Typically, the values of the resistors used to build the voltage divider are selected to ensure that minimum load current is maintained.
2
www.irf.com
Rev. 1.8 02/04/03
IRU1117
PIN DESCRIPTIONS
PIN # 1 2 PIN SYMBOL PIN DESCRIPTION Adj A resistor divider from this pin to the VOUT pin and ground sets the output voltage. VOUT The output of the regulator. A minimum of 10mF capacitor must be connected from this pin to ground to insure stability. The 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 dropout voltage during the load transient response. This pin must always be 1.3V higher than VOUT in order for the device to regulate properly.
3
VIN
BLOCK DIAGRAM
VIN 3 2 VOUT
+
1.25V CURRENT LIMIT
+
THERMAL SHUTDOWN
1 Adj
Figure 2 - Simplified block diagram of the IRU1117.
APPLICATION INFORMATION
Introduction The IRU1117 adjustable Low Dropout (LDO) regulator is a three-terminal device which can easily be programmed with the addition of two external resistors to any voltages within the range of 1.25 to 5.5V. This regulator only needs 1.3V differential to maintain output regulation. Unlike the first generation of the three-terminal regulators such as LM117 that required 3V differential between the input and the regulated output. The IRU1117 is specifically designed to meet the fast current transient needs as well as providing an accurate initial voltage, reducing the overall system cost with the need for fewer output capacitors. This is a key requirement for today's low voltage IC applications that typically need 3.3V supply and are often generated from the 5V supply. Other applications such as high speed memory termination need to switch the load current from zero to full load in tens of nanoseconds at their pins, which translates to an approximately 300 to 500ns current step at the regulator. In addition, the output voltage tolerances are sometimes tight and they include the transient response as part of the specification.
Rev. 1.8 02/04/03
www.irf.com
3
IRU1117
Output Voltage Setting The IRU1117 can be programmed to any voltages in the range of 1.25V to 5.5V with the addition of R1 and R2 external resistors according to the following formula: VOUT = VREF3 1+ to the load side, the effective resistance between the regulator and the load is multiplied by the factor of (1+R2/ R1), or the effective resistance will be RP(eff)=RP3(1+R2/ R1). It is important to note that for high current applications, this can represent a significant percentage of the overall load regulation and one must keep the path from the regulator to the load as short as possible to minimize this effect.
PARASITIC LINE RESISTANCE
(
R2 R1
) +IADJ3R2
Where: VREF = 1.25V Typically IADJ = 50mA Typically R1 and R2 as shown in Figure 3:
RP
VIN
VIN
VOUT
IRU1117
VIN
VIN VOUT
VOUT
Adj
IRU1117
Adj VREF R1
R1
RL
R2
IADJ = 50uA
R2
Figure 4 - Schematic showing connection for best load regulation. Figure 3 - Typical application of the IRU1117 for programming the output voltage. The IRU1117 keeps a constant 1.25V between the output pin and the adjust pin. By placing a resistor R1 across these two pins a constant current flows through R1, adding to the IADJ current and into the R2 resistor producing a voltage equal to the (1.25/R1)3R2 + IADJ3R2 which will be added to the 1.25V to set the output voltage. This is summarized in the above equation. Since the minimum load current requirement of the IRU1117 is 10mA, R1 is typically selected to be 121V resistor so that it automatically satisfies the minimum current requirement. Notice that since IADJ is typically in the range of 50mA it only adds a small error to the output voltage and should only be considered when a very precise output voltage setting is required. For example, in a typical 3.3V application where R1=121V and R2=200V the error due to IADJ is only 0.3% of the nominal set point. Load Regulation Since the IRU1117 is only a three-terminal device, it is not possible to provide true remote sensing of the output voltage at the load. Figure 4 shows that the best load regulation is achieved when the bottom side of R2 is connected to the load and the top side of R1 resistor is connected directly to the case or the VOUT pin of the regulator and not to the load. In fact, if R1 is connected Stability The IRU1117 requires the use of an output capacitor as part of the frequency compensation in order to make the regulator stable. Typical designs for microprocessor applications use standard electrolytic capacitors with a typical ESR in the range of 50 to 100mV and an output capacitance of 500 to 1000mF. Fortunately as the capacitance increases, the ESR decreases resulting in a fixed RC time constant. The IRU1117 takes advantage of this phenomenon in making the overall regulator loop stable. For most applications a minimum of 100mF aluminum electrolytic capacitor such as Sanyo MVGX series, Panasonic FA series as well as the Nichicon PL series insures both stability and good transient response. Thermal Design The IRU1117 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 heat sink be selected such that during maximum continuous load operation the junction temperature is kept below this number. The example below for a SCSI terminator application shows the steps in selecting the proper regulator in a surface-mount package. (See IRU1015 for non-surface-mount packages)
4
www.irf.com
Rev. 1.8 02/04/03
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 dropout 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. The steps for selecting the right package with proper board area for heat sinking to keep the junction temperature below 1358C is given as: 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 uJA allowed for our example: TJ - TA 135 - 35 uJA(MAX) = = = 75.68C/W 1.32 PD 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 70C/W which is lower than the calculated number.
R2 154 1%
To set the output DC voltage, we need to select R1 and R2: 4) Assuming R1 = 121V, 1%: R2 =
( VOUT -1)3R1 =( 2.85 -1) 3121 = 154.8V VREF 1.25
Select R2 = 154V, 1% 5) Calculate the power dissapation for the schottky diode (D1): PD = VF 3 IOUT PD = 0.5 3 0.8 = 0.4W and select a suitable component.
D1
5V
C1 10uF
VIN
VOUT
2.85V
C2 22uF R1 121 1%
IRU1117
Adj
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 recommended 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.
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. 1.8 02/04/03
www.irf.com
5
IRU1117
(D) TO-252 Package 2-Pin
A C B K L M 458 D E O J N 78
Q
P
F H
G
R
S
R1 SYMBOL MIN MAX A 6.477 6.731 B 5.004 5.207 C 0.686 0.838 D 7.417 8.179 E 9.703 10.084 F 0.635 0.889 2.286 BSC G H 4.521 4.623 J &1.52 &1.62 K 2.184 2.388 L 0.762 0.864 M 1.016 1.118 N 5.969 6.223 O 1.016 1.118 P 0 0.102 Q 0.534 0.686 R R0.31 TYP R1 R0.51 TYP S 0.428 0.588
C L
NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS.
6
www.irf.com
Rev. 1.8 02/04/03
IRU1117
(P) Ultra Thin-PakTM 2-Pin
A A1 K E U
V B H M L P G G1 N C C L R D
SYMBOL A A1 B C D E G G1 H K L M N P R U V
MIN MAX 5.91 6.17 5.54 5.79 6.02 6.27 1.70 2.03 0.63 0.79 0.17 0.33 2.16 2.41 4.45 4.70 9.42 9.68 0.76 1.27 0.02 0.13 0.89 1.14 0.25 0.25 0.94 1.19 28 68 2.92 3.30 5.08 NOM
NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS.
Rev. 1.8 02/04/03
www.irf.com
7
IRU1117
(S) SOIC Package 8-Pin Surface Mount, Narrow Body
H A B C
E
DETAIL-A PIN NO. 1 D 0.386 0.015 x 458 T K F J
L
DETAIL-A
I
G 8-PIN SYMBOL A B C D E F G H I J K L T MIN MAX 4.80 4.98 1.27 BSC 0.53 REF 0.36 0.46 3.81 3.99 1.52 1.72 0.10 0.25 78 BSC 0.19 0.25 5.80 6.20 08 88 0.41 1.27 1.37 1.57
NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS.
8
www.irf.com
Rev. 1.8 02/04/03
IRU1117
(Y) SOT-223 Package 3-Pin
D B
E
H
e e1
S
SYMBOL A A1 B B1 C D E e e1 H Q Q1 Q2 S T
MIN 1.498 0.02 2.895 0.637 0.239 6.299 3.30 2.209 4.496 6.70 08 78 78 0.838 1.092
MAX 1.702 0.11 3.15 0.85 0.381 6.706 3.708 2.953 4.699 7.30 108 168 168 1.05 1.30
NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS.
Q1
T
A
Q C Q2
B1
A1
Rev. 1.8 02/04/03
www.irf.com
9
IRU1117
PACKAGE SHIPMENT METHOD
PKG DESIG D P S Y PACKAGE DESCRIPTION TO-252, (D-Pak) Ultra Thin-Pak SOT-223
TM
PIN COUNT 2 2 8 3
PARTS PER TUBE 75 75 95 80
PARTS PER REEL 2500 2500 2500 2500
T&R Orientation Fig A Fig B Fig C Fig D
SOIC, Narrow Body
1
1
1
1
1
1
Feed Direction Figure A
Feed Direction Figure B
1
1
1
1
1
1
Feed Direction Figure C
Feed Direction Figure D
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
10
www.irf.com
Rev. 1.8 02/04/03

▲Up To Search▲

Price & Availability of IRU1117CS

	To Download IRU1117CS Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .