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FAN1581
5A Adjustable/Fixed Ultra Low Dropout Linear Regulator
Features
* * * * * * * Ultra Low dropout voltage, 0.4V typical at 5A Remote sense operation Fast transient response Load regulation: 0.05% typical 0.5% initial accuracy On-chip thermal limiting 5-Pin SPAK and TO-263 packages
Description
The FAN1581, FAN1581-1.5, and FAN1581-2.5 are ultra-low dropout regulators with 5A output current capability. These devices have been optimized for low voltage applications including VTT bus termination, where transient response and minimum input voltage are critical. The FAN1581 is ideal for low voltage microprocessor applications requiring a regulated output from 1.3V to 5.7V with a power input supply of 1.75V to 6.5V. The FAN1581-1.5 offers fixed 1.5V with 5A current capabilities for GTL+ bus VTT termination. The FAN1581-2.5 offers fixed 2.5V with 5A current capability for logic IC operation and processors while minimizing the overall power dissipation. Current limit ensures controlled short-circuit current. On-chip thermal limiting provides protection against any combination of overload and ambient temperature that would create excessive junction temperatures. The FAN1581 series regulators are available in the 5-Pin SPAK and TO-263 power packages.
Applications
* * * * * * * Pentium(R) Processors PowerPCTM, AMD K5 and K6 processors Pentium support of GTL+ bus supply Low voltage logic supply Embedded Processor supplies Split plane regulator New 2.5V and 1.8V Logic Families
Typical Applications
VIN = 3.3V + 10F VIN = 3.3V + 10F VCNTL = 5V VCNTL = 5V + 1F 2.1V at 5A + 124 22F VIN = 5.75V + 86.6 10F VCNTL = 12V VIN VSENSE VIN VSENSE FAN1581-2.5 VOUT VCNTL GND
2.5V at 5A + 22F
VIN
VSENSE
FAN1581 VOUT VCNTL Adj
FAN1581 VOUT VCNTL Adj 124 + 22F
5V at 5A
374
Pentium is a registered trademark of Intel Corporation. PowerPC is a trademark of IBM Corporation.
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FAN1581
PRODUCT SPECIFICATION
Pin Assignments
FAN1581M-1.5, -2.5 FRONT VIEW FAN1581M FRONT VIEW FAN1581P FRONT VIEW FAN1581P-1.5, -2.5 FRONT VIEW
1 2 345
1 2 345
123
45
123
45
CNTL IN
S GND OUT CNTL IN
S ADJ OUT CNTL IN
5-Lead Plastic TO-263 JC=3C/W* Tab is out.
5-Lead Plastic SPAK JC=2C/W* Tab is out.
*With package soldered to 0.5 square inch copper area over backside ground plane or internal power plane. JA can vary fom 20C/W to >40C/W with other mounting techniques.
Pin Definitions
Pin Number
1
Pin Name VSense ADJ/GND
Pin Function Descrition Remote Voltage Sense. Connect this pin to the load to permit true remote sensing and avoid trace drops. Adjust or Ground. On the FAN1581, this pin forms the feedback to determine the output voltage. On the FAN1581-1.5 and -2.5, connect this pin to ground. Output Voltage. This pin and the tab are output. Control Voltage. This pin draws small-signal power to control the FAN1581 circuitry. Connect to a voltage higher than VIN, as shown in the applications circuits. Input Voltage.
2
3 4
VOUT VCNTL
5
VIN
Internal Block Diagram
4 VCNTL, Control 5 Vin, Power
Thermal Shutdown Current Limit 3 Output 1 Sense 2 Adj
Vref
Voltage Loop Amplifier
2
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CNTL IN
S ADJ OUT
S GND OUT
PRODUCT SPECIFICATION
FAN1581
Absolute Maximum Ratings
Parameter VIN VCNTL Operating Junction Temperature Range Lead Temperature (Soldering, 10 sec.) Storage Temperature Range -65 0 Min. Max. 7 13.2 125 300 150 Unit V V C C C
Electrical Characteristics
TJ=25C, VOUT = VS, VADJ = 0V unless otherwise specified. The * denotes specifications which apply over the specified operating temperature range. Parameter Reference Voltage3 Reference Voltage3 Conditions VIN = 2.0V, VCNTL = 2.75V, IOUT = 10mA 2.05V VIN 5.5V, 2.7V VCNTL 12V, 10mA IOUT 5A 3V VIN 7V (function of Vout), 10mA IOUT 5A 3V VIN 7V, 10mA IOUT 5A 5.1V VIN 7V, 10mA IOUT 5A 1.75V VIN 5.5V, 2.5V VCNTL 12V, IOUT = 10mA VIN = 2.1V, VCNTL = 2.75V, 10mA IOUT 5A VIN = 2.05V, VREF = 1%, IOUT = 5A VCNTL = 2.75V, VREF = 1%, IOUT = 5A VCNTL = 2.75V, VREF = 1%, IOUT = 5A VIN = 2.05V, VCNTL = 2.75V VIN = 2.05V, VCNTL = 2.75V, IOUT = 10mA VIN = 2.05V, VCNTL = 2.75V VIN = 3.3V, VCNTL = 5V VIN = 3.75V, VCNTL = 3.75V, f = 120Hz, COUT = 22F Tantalum, IOUT = 2.5A TO-263 SPAK TA = 25C, 30ms pulse Min. 1.243 * 1.237 Typ. 1.250 1.250 Max. 1.257 1.263 Units V V
Adjustable Output Voltage Output Voltage4 Output Voltage5 Line Regulation1,2 Load Regulation1,2 Dropout Voltage Minimum (VCNTL-VOUT) Dropout Voltage Minimum (VIN-VOUT) Dropout Voltage Minimum VIN Current Limit Control Pin Current Adjust Pin Current3 Minimum Load Current Ripple Rejection Thermal Resistance, Junction to Case Thermal Regulation Thermal Shutdown
* * * * * *
Vref 1.47 2.474
1.5 1.5 2.5 1 1 1.05 0.4
5.7 1.53 2.526 3 5 1.18 0.5 0.6
V V V mV mV V V V A mA A mA dB C/W
* * * * * 60 5.2
0.5
2 50 5.0 80 3 2 0.002 150
6 120 10
0.02
%/W C
Notes: 1. See thermal regulation specifications for changes in output voltage due to heating effects. Load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. 2. Line and load regulation are guaranteed up to the maximum power dissipation (18W). Power dissipation is determined by input/output differential and the output current. Guaranteed maximum output power will not be available over the full input/ output voltage range. 3. FAN1581 only. 4. FAN1581-1.5 only. 5. FAN1581-2.5 only.
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3
FAN1581
PRODUCT SPECIFICATION
Typical Perfomance Characteristics
OUTPUT VOLTAGE DEVIATION (%) 1.0 0.9 DROPOUT VOLTAGE (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 1 2 3 4 5 OUTPUT CURRENT (A) Dropout Voltage vs. Output Current 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 -75 -50 -25 0 25 50 75 100 125 150 175 JUNCTION TEMPERATURE (C) Load Regulation vs. Temperature =5A
T=0C T=25C T=125C
1.275 REFERENCE VOLTAGE 1.265 1.260 1.255 1.250 1.245 1.240 1.235 1.230 1.225 -75 -50 -25 0 25 50 75 100 125 150 175 JUNCTION TEMPERATURE (C) Reference Voltage vs. Temperature OUTPUT VOLTAGE (V) 1.270
3.70 3.65 3.60 3.55 3.50 3.45 3.40 3.35 3.30 3.25 3.20
VOUT set with 1% resistors
VOUT = 3.3V1 -75 -50
Note: 1. FAN1581 Only
-25 0 25 50 75 100 125 150 175 JUNCTION TEMPERATURE (C) Output Voltage vs. Temperature
MINIMUM LOAD CURRENT (mA)
10 ADJUST PIN CURRENT (A) 8 6 4 2 0 -75 -50 -25 0 25 50 75 100 125 150 175 JUNCTION TEMPERATURE (C) Mimimum Load Current vs. Temperature
100 90 80 70 60 50 40 30 20 10 0 -75 -50 -25 0 25 50 75 100 125 150 175 JUNCTION TEMPERATURE (C) Adjust Pin Current vs. Temperature Note: 1. FAN1581 Only
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PRODUCT SPECIFICATION
FAN1581
Typical Perfomance Characteristics (continued)
11 SHORT-CIRCUIT CURRENT (A) 90 90 9 RIPPLE REJECTIONS (dB) 70 60 50 40 30 20 10 3 -75 -50 -25 0 25 50 75 100 125 150 175 JUNCTION TEMPERATURE (C) Short-Circuit Current vs.Temeperature 20 0 10 100 1K 10K FREQUENCY (HZ) 100K (VIN--VOUT) 3V 0.5V VRIPPLE 2V IOUT = 5A
7
5
Ripple Rejection vs. Frequency
15 POWER (W)
10
5
0 25 45 65 85 105 CASE TEMPERATURE 125
Maximum Power Dissipation
General
The FAN1581, FAN1581-1.5, and FAN1581-2.5 are threeterminal regulators optimized for GTL+ VTT termination and logic applications. These devices are short-circuit protected, and offer thermal shutdown to turn off the regulator when the junction temperature exceeds about 150C. The FAN1581 series provides low dropout voltage and fast transient response. Frequency compensation uses capacitors with low ESR while still maintaining stability. This is critical in addressing the needs of low voltage high speed microprocessor buses like GTL+.
to ensure stability. The frequency compensation of these devices optimizes the frequency response with low ESR capacitors. In general, it is suggested to use capacitors with an ESR of <1. It is also recommended to use bypass capacitors such as a 22F tantalum or a 100F aluminum on the adjust pin of the FAN1581 for low ripple and fast transient response. When these bypassing capacitors are not used at the adjust pin, smaller values of output capacitors provide equally good results.
Protection Diodes
In normal operation, the FAN1581 series does not require any protection diodes. For the FAN1581, internal resistors limit internal current paths on the adjust pin. Therefore, even with bypass capacitors on the adjust pin, no protection diode is needed to ensure device safety under short-circuit conditions.
Stability
The FAN1581 series requires an output capacitor as a part of the frequency compensation. It is recommended to use a 22F solid tantalum or a 100F aluminum electrolytic on the output
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FAN1581
PRODUCT SPECIFICATION
A protection diode between the input and output pins is usually not needed. An internal diode between the input and the output pins on the FAN1581 series can handle microsecond surge currents of 50A to 100A. Even with large value output capacitors it is difficult to obtain those values of surge currents in normal operation. Only with large values of output capacitance, such as 1000F to 5000F, and with the input pin instantaneously shorted to ground can damage occur. A crowbar circuit at the input can generate those levels of current; a diode from output to input is then recommended, as shown in Figure 1. Usually, normal power supply cycling or system "hot plugging and unplugging" will not generate current large enough to do any damage. The adjust pin can be driven on a transient basis 7V with respect to the output, without any device degradation. As with any IC regulator, exceeding the maximum input-to-output voltage differential causes the internal transistors to break down and none of the protection circuitry is then functional.
D1 1N4002 (OPTIONAL)
100 and the ripple frequency equals 120Hz, the adjust pin capacitor should be 22F. At 10kHz, only 0.22F is needed.
Output Voltage
The FAN1581 regulator develops a 1.25V reference voltage between the output pin and the adjust pin (see Figure 2). Placing a resistor R1 between these two terminals causes a constant current to flow through R1 and down through R2 to set the overall output voltage. Normally, this current is the specified minimum load current of 10mA. The current out of the adjust pin adds to the current from R1 and is typically 50A. Its output voltage contribution is small and only needs consideration when a very precise output voltage setting is required.
Vcntl VIN + C1 10F IADJ 50A VOUT = VREF (1+R2/R1) + IADJ (R2) Vcntl Vsense VOUT VREF + R1 C2 22F
FAN1581 Vin Adj Vout
R2
VOUT VIN + C1 10F
Vcntl Vin
Vsense + R1 Adj Vout VOUT C2 22F
FAN1581
Figure 2. Basic Regulator Circuit
Load Regulation
+ CADJ R2
D1 1N4002 (OPTIONAL)
The FAN1581 family provides true remote sensing, eliminating output voltage errors due to trace resistance. To utilize remote sensing, connect the VSENSE pin directly to the load, rather than at the VOUT pin. If the load is more than 1" away from the FAN1581, it may be necessary to increase the load capacitance to ensure stability.
VCNTL VIN + C1 10F
Thermal Considerations
Vcntl Vin Vsense + VOUT C2 22F Gnd Vout FAN1581-1.5, 2.5
Figure 1. Optional Protection Diode
Ripple Rejection
In applications that require improved ripple rejection, a bypass capacitor from the adjust pin of the FAN1581 to ground reduces the output ripple by the ratio of VOUT/1.25V. The impedance of the adjust pin capacitor at the ripple frequency should be less than the value of R1 (typically in the range of 100 to 120) in the feedback divider network in Figure 1. Therefore, the value of the required adjust pin capacitor is a function of the input ripple frequency. For example, if R1 equals
The FAN1581 series protect themselves under overload conditions with internal power and thermal limiting circuitry. However, for normal continuous load conditions, do not exceed maximum junction temperature ratings. It is important to consider all sources of thermal resistance from junction-toambient. These sources include the junction-to-case resistance, the case-to-heat sink interface resistance, and the heat sink resistance. Thermal resistance specifications have been developed to more accurately reflect device temperature and ensure safe operating temperatures. The electrical characteristics section provides a separate thermal resistance and maximum junction temperature for both the control circuitry and the power transistor. Calculate the maximum junction temperature for both sections to ensure that both thermal limits are met. For example, look at using an FAN1581M-1.5 to generate 5A @ 1.5V 2% from a 3.3V source (3.2V to 3.6V).
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REV. 1.0.2 8/15/01
PRODUCT SPECIFICATION
FAN1581
Assumptions: * * * * * Vin = 3.6V worst case VOUT = 1.47V worst case IOUT = 5A continuous TA = 40C Case-to-Ambient = 5C/W (assuming both a heatsink and a thermally conductive material)
From the specification table, TJ = TA + (PD) * ( Case-to-Ambient + JC) = 40 + (10.65) * (5 + 3) = 125C The junction temperature is within the maximum rating. Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below the die. This is the lowest resistance path for heat flow. Proper mounting ensures the best thermal flow from this area of the package to the heat sink. Use of a thermally conductive material at the case-to-heat sink interface is recommended. Use a thermally conductive spacer if the case of the device must be electrically isolated and include its contribution to the total thermal resistance.
The power dissipation in this application is: PD = (VIN - VOUT) * (IOUT) = (3.6-1.47) * (5) = 10.65W
U1 VIN = 3.3V 10F + C1 VIN VSENSE
FAN1581 VOUT VCNTL Adj 10F C3 R1 + 124 100F C2
2.1V at 5A
VCNTL = 5V 1F C4
R2
86.6
Figure 3. Application Circuit (FAN1581) Table 1. Bill of Materials for Application Circuit for the FAN1581
Item C1, C3 C2 C4 R1 R2 U1
Quantity 2 1 1 1 1 1
Manufacturer Xicon Xicon Any Generic Generic Fairchild
Part Number L10V10 L10V100
Description 10F, 10V Aluminum 100F, 10V Aluminum 1F Ceramic 124, 1% 86.6, 1%
FAN1581P
5A Regulator
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7
FAN1581
PRODUCT SPECIFICATION
U1 VIN = 2.5V 10F C1 VCNTL = 3.3V 1F C2 + VIN VSENSE
FAN1581-1.5 VOUT VCNTL GND
1.5V at 5A + 100F C3
Figure 4. Application Circuit (FAN1581-1.5) Table 2. Bill of Materials for Application Circuit for the RC1581-1.5
Item C1 C2 C3 U1
Quantity 1 1 1 1
Manufacturer Xicon Any Xicon Fairchild
Part Number L10V10 L10V100 FAN1581P-1.5
Description 10F, 10V Aluminum 1F Ceramic 100F, 10V Aluminum 5A Regulator
U1 VIN = 3.3V + 10F C1 VCNTL = 5V + 1F C2 VIN VSENSE
FAN1581-2.5 VOUT VCNTL GND
2.5V at 5A + 100F C3
Figure 5. Application Circuit (FAN1581-2.5) Table 3. Bill of Materials for Application Circuit for the RC1581-2.5
Item C1 C2 C3 U1
Quantity 1 1 1 1
Manufacturer Xicon Any Xicon Fairchild
Part Number L10V10 L10V100 FAN1581P-2.5
Description 10F, 10V Aluminum 1F Ceramic 100F, 10V Aluminum 5A Regulator
8
REV. 1.0.2 8/15/01
PRODUCT SPECIFICATION
FAN1581
Mechanical Dimensions
5-Lead TO-263 Package
Notes: 1. Dimensions are exclusive of mold flash and metal burrs. 2. Standoff-height is measured from lead tip with ref. to Datum -B-. 3. Foot length is measured with ref. to Datum -A- with lead surface (at inner R). 4. Dimension exclusive of dambar protrusion or intrusion. 5. Formed leads to be planar with respect to one another at seating place -C-.
Symbol
Inches Min. Max. .405 .625 .380 .055 .039 .072 .055 .190 0.110 .029 .019
Millimeters Min. 9.65 14.60 8.25 - .50 1.52 1.14 4.06 2.28 .457 0.43 Max. 10.29 15.88 9.66 1.40 .99 1.83 1.40 4.83 2.80 .736 0.48
A B C D E F G H J K R
.380 .575 .325 - .020 .060 0.45 .160 .090 .018 .017
A
D
G C B E-PIN
E F
R (2PLCS) J
-B-
-A-
H -C-
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9
FAN1581
PRODUCT SPECIFICATION
Mechanical Dimensions (continued)
SPAK Package
Notes: 1. All linear dimensions are in inches (millimeters). 2. This drawing is subject to change without notice. 3. The center lead is in electrical contact with the thermal tab. 4. Dimensions do not include mold protrusions, not to exceed 0.006 (0,15).
Symbol A B b1 b2 C c1 c2 D E e L L1 L2 L3 R
Inches Min. Max.
Millimeters Min. Max.
Notes
0.350 0.360 0.220 NOM 0.268 0.025 0.031 0.080 0.070 0.040 0.050 0.010 NOM 0.295 NOM 0.365 0.375 0.067 0.410 0.420 0.031 0.041 0.350 0.360 0.310 0.320 0.010 NOM 0 8
8.89 9.14 5.59 NOM 6.81 0.63 0.79 2.03 1.78 1.02 1.27 0.25 NOM 7.49 NOM 9.27 9.52 1.72 10.41 10.67 0.79 1.04 8.89 9.14 7.87 8.13 0.25 NOM 0 8
E A B
C c1 c2
D L L3 L2 Thermal Ta b (See Note 3)
1 e b1
5 b2 0.010 (0,25) M Seating Plane 0.004 (0,10) 0.005 (0.13) 0.001 (0.03)
R
L1
Gage Plane
3-6
10
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FAN1581
PRODUCT SPECIFICATION
Ordering Information
Product Number FAN1581M FAN1581P FAN1581M-1.5 FAN1581P-1.5 FAN1581M-2.5 FAN1581P-2.5 Package TO-263 SPAK TO-263 SPAK TO-263 SPAK
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user.
www.fairchildsemi.com 8/15/01 0.0m 002 Stock#DS30001584 2001 Fairchild Semiconductor Corporation
2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

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