LT1585A/LT1585A-3.3 5A Low Dropout Fast Response Positive Regulators Adjustable and Fixed U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ Fast Transient Response Guaranteed Dropout Voltage at Multiple Currents Load Regulation: 0.05% Typ Trimmed Current Limit On-Chip Thermal Limiting Standard 3-Pin Power Package U APPLICATIONS ■ ■ ■ ■ ■ ■ Pentium® Processor Supplies PowerPCTM Supplies Other 2.5V to 3.6V Microprocessor Supplies Low Voltage Logic Supplies Battery-Powered Circuitry Post Regulator for Switching Supply The LT ®1585A/LT1585A-3.3 are low dropout 3-terminal regulators with 5A output current capability. Design has been optimized for low voltage applications where transient response and minimum input voltage are critical. Similar to the LT1084 family, these regulators feature lower dropout voltage and faster transient response. These improvements make them ideal for low voltage microprocessor applications requiring a regulated 2.5V to 3.6V output with an input supply below 7V. Current limit is trimmed to ensure specified output current and controlled short-circuit current. On-chip thermal limiting provides protection against any combination of overload that would create excessive junction temperatures. LT1585ACT Adjustable LT1585ACT-3.3 3.3V Fixed The LT1585A/LT1585A-3.3 are available in the industry standard 3-pin TO-220 power package. , LTC and LT are registered trademarks of Linear Technology Corporation. Pentium is a registered trademark of Intel Corporation. PowerPC is a trademark of IBM Corporation. U TYPICAL APPLICATION 3.3V, 5A Regulator Dropout Voltage vs Output Current 1.5 LT1585A-3.3 + C1 10µF + C2* 10µF * REQUIRED FOR STABILITY 1585A TA01 NOTE: MICROPROCESSOR APPLICATIONS WITH LOAD TRANSIENTS OF 3.8A REQUIRE OUTPUT DECOUPLING CAPACITANCE >1300µF ON FIXED VOLTAGE PARTS TO ACHIEVE < 50mV OF DEVIATION FROM NOMINAL OUTPUT. CONSULT FACTORY FOR DETAILS 1.4 INPUT/OUTPUT DIFFERENTIAL (V) VIN ≥ 4.75V 3.3V 5A 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0 IFULL LOAD OUTPUT CURRENT (A) LT1585A TA02 1 LT1585A/LT1585A-3.3 W W U W ABSOLUTE MAXIMUM RATINGS Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C UU U VIN ............................................................................. 7V Operating Junction Temperature Range Control Section.................................... 0°C to 125°C Power Transistor ................................. 0°C to 150°C PRECONDITIONI G 100% Thermal Limit Functional Test W U U PACKAGE/ORDER INFORMATION ORDER PART NUMBER FRONT VIEW 3 VIN 2 VOUT 1 ADJ LT1585ACT T PACKAGE 3-LEAD PLASTIC TO-220 ORDER PART NUMBER FRONT VIEW 3 VIN 2 VOUT 1 GND LT1585ACT-3.3 T PACKAGE 3-LEAD PLASTIC TO-220 θJA = 50°C/W θJA = 50°C/W Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS Reference Voltage LT1585A (VIN – VOUT) = 3V, TJ = 25°C, IOUT = 10mA 1.5V ≤ (VIN – VOUT) ≤ 5.75V, 10mA ≤ IOUT ≤ 5A VIN = 5V, TJ = 25°C, IOUT = 0mA 4.75V ≤ VIN ≤ 7V, 0mA ≤ IOUT ≤ 5A Output Voltage LT1585A-3.3 Line Regulation (Notes 1, 2) LT1585A LT1585A-3.3 2.75V ≤ VIN ≤ 7V, IOUT = 10mA 4.75V ≤ VIN ≤ 7V, IOUT = 0mA Load Regulation (Notes 1, 2, 3) LT1585A LT1585A-3.3 (VN – VOUT) = 3V, TJ = 25°C, 10mA ≤ IOUT ≤ IFULL LOAD VIN = 5V, TJ = 25°C, 0mA ≤ IOUT ≤ IFULL LOAD Dropout Voltage Current Limit (Note 3) LT1585A LT1585A-3.3 MIN TYP MAX UNITS ● 1.238 (–1%) 1.225 (–2%) 1.250 1.250 1.262 (+1%) 1.275 (+2%) V V ● 3.267 (–1%) 3.235 (– 2%) 3.300 3.300 3.333 (+1%) 3.365 (+ 2%) V V ● 0.005 0.2 % ● 0.05 0.05 0.3 0.5 % % ● 1.150 1.300 V ● 1.200 1.400 V ∆VREF = 1%, IOUT = 3A ∆VOUT = 1%, IOUT = 3A LT1585A LT1585A-3.3 ∆VREF = 1%, IOUT = 5A ∆VOUT = 1%, IOUT = 5A LT1585A LT1585A-3.3 (VIN – VOUT) = 5.5V (VIN – VOUT) = 5.5V ● 5.0 6.0 A ● 55 120 µA Adjust Pin Current LT1585A Change (Note 3) 1.5V ≤ (VIN – VOUT) ≤ 5.75V, 10mA ≤ IOUT ≤ IFULL LOAD ● 0.2 5 µA Minimum Load Current 1.5V ≤ (VIN – VOUT) ≤ 5.75V ● 2 10 mA VIN = 5V ● 8 13 mA Adjust Pin Current LT1585A LT1585A Quiescent Current LT1585A-3.3 2 LT1585A/LT1585A-3.3 ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS Ripple Rejection LT1585A LT1585A-3.3 f = 120Hz, COUT = 25µF Tant., (VIN – VOUT) = 3V, IOUT = 5A f = 120Hz, COUT = 25µF Tant., VIN = 6.3V, IOUT = 5A LT1585A LT1585A-3.3 TA = 25°C, 30ms Pulse TA = 25°C, 30ms Pulse ● Thermal Regulation MIN TYP 60 72 0.004 Temperature Stability TA = 125°C, 1000 Hrs. 0.03 RMS Output Noise (% of VOUT) TA = 25°C, 10Hz ≤ f ≤ 10kHz 0.003 LT1585A T Package: Control Circuitry/Power Transistor The ● denotes specifications which apply over the specified operating temperature range. Note 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. Note 2: Line and load regulation are guaranteed up to the maximum power dissipation 28.8W for the LT1585A in T package. Power dissipation is UNITS dB 0.02 %/W 1.0 % 0.5 ● Long-Term Stability Thermal Resistance Junction to Case MAX % % 0.7/3.0 °C/W determined by input/output differential and the output current. Guaranteed maximum output power will not be available over the full input/output voltage range. Note 3: IFULL LOAD is defined as the maximum value of output load current as a function of input-to-output voltage. IFULL LOAD is equal to 5A for the LT1585A/LT1585A-3.3. The LT1585A has constant current limit with changes in input-to-output voltage. U W TYPICAL PERFORMANCE CHARACTERISTICS LT1585A Short-Circuit Current vs Temperature LT1585A Dropout Voltage vs Output Current 0.10 6.0 1.5 T = –5°C 1.2 1.1 T = 125°C 1.0 T = 25°C 0.9 0.8 0.7 OUTPUT VOLTAGE DEVIATION (%) 1.3 SHORT-CIRCUIT CURRENT (A) GUARANTEED TEST POINTS 1.4 DROPOUT VOLTAGE (V) LT1585A Load Regulation vs Temperature 5.5 5.0 4.5 ∆I = 5A 0.05 0 –0.05 –0.10 –0.15 0.6 0.5 0 1 3 4 2 OUTPUT CURRENT (A) 5 LT1585A • TPC01 4.0 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1585A • TPC02 –0.20 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1585A • TPC03 3 LT1585A/LT1585A-3.3 U W TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Temperature Using Adjustable LT1585A 3.70 1.270 3.65 1.265 3.60 1.260 1.255 1.250 1.245 1.240 LT1585A-3.3 Output Voltage vs Temperature 3.35 VOUT SET WITH 1% RESISTORS 3.34 VOUT = 3.6V 3.33 OUTPUT VOLTAGE (V) 1.275 OUTPUT VOLTAGE (V) REFERENCE VOLTAGE (V) LT1585A Reference Voltage vs Temperature 3.55 3.50 VOUT = 3.45V 3.45 VOUT = 3.38V 3.40 3.35 VOUT = 3.3V 3.32 3.31 VOUT = 3.3V 3.30 3.29 3.28 3.27 1.235 3.30 1.230 3.25 3.26 1.225 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 3.20 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 3.25 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1585A • TPC04 LT1585A Minimum Load Current vs Temperature 2 1 100 13 90 12 80 QUIESCENT CURRENT (mA) ADJUST PIN CURRENT (µA) MINIMUM LOAD CURRENT (mA) 3 LT1585A-3.3 Quiescent Current vs Temperature LT1585A Adjust Pin Current vs Temperature 5 4 LT1585A • TPC06 LT1585A • TPC05 70 60 50 40 30 20 9 8 7 6 5 4 10 0 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 11 10 0 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1585A • TPC07 3 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1585A • TPC09 LT1585A • TPC08 LT1585A Maximum Power Dissipation* LT1585A-3.3 Ripple Rejection vs Frequency 90 30 80 60 20 POWER (W) RIPPLE REJECTION (dB) 25 70 50 40 30 15 10 20 LT1585A-3.3: (VIN – VOUT) ≤ 3V 0.5V ≤ VRIPPLE ≤ 2V IOUT = IFULL LOAD 10 0 5 0 10 100 1k 10k FREQUENCY (Hz) 100k LT1585A • TPC10 50 60 70 80 90 100 110 120 130 140 150 CASE TEMPERATURE (˚C) LT1585A • TPC11 *AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE 4 LT1585A/LT1585A-3.3 W W SI PLIFIED SCHE ATIC VIN + – THERMAL LIMIT VOUT ADJ GND LT1585A • BD FOR FIXED VOLTAGE DEVICE U W U U APPLICATIONS INFORMATION General The LT1585A/LT1585A-3.3 3-terminal regulators are easy to use and have all the protection features expected in high performance linear regulators. The devices are short-circuit protected, safe-area protected and provide thermal shutdown to turn off the regulators should the junction temperature exceed about 150°C. The regulators include an adjustable and a fixed 3.3V version. These ICs are pin compatible with the LT1083/LT1084/ LT1085 family of linear regulators but offer lower dropout voltage and faster transient response. The trade-off for this improved performance is a 7V maximum supply voltage. Similar to the LT1083/LT1084/LT1085 family, the LT1585A/LT1585A-3.3 regulators require an output capacitor for stability. However, the improved frequency compensation permits the use of capacitors with much lower ESR while still maintaining stability. This is critical in addressing the needs of modern, low voltage, high speed microprocessors. Current generation microprocessors cycle load current from almost zero to amps in tens of nanoseconds. Output voltage tolerances are tighter and include transient response as part of the specification. The LT1585A/ LT1585A-3.3 are specifically designed to meet the fast current load-step requirements of these microprocessors and save total cost by needing less output capacitance in order to maintain regulation. Stability The circuit design in the LT1585A/LT1585A-3.3 requires the use of an output capacitor as part of the frequency compensation. For all operating conditions, the addition of a 22µF solid tantalum or a 100µF aluminum electrolytic on the output ensures stability. Normally, the LT1585A/ LT1585A-3.3 can use smaller value capacitors. Many different types of capacitors are available and have widely varying characteristics. These capacitors differ in capaci- 5 LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION tor tolerance (sometimes ranging up to ±100%), equivalent series resistance, equivalent series inductance and capacitance temperature coefficient. The LT1585A/ LT1585A-3.3 frequency compensation optimizes frequency response with low ESR capacitors. In general, use capacitors with an ESR of less than 1Ω. On the adjustable LT1585A, bypassing the adjust terminal improves ripple rejection and transient response. Bypassing the adjust pin increases the required output capacitor value. The value of 22µF tantalum or 100µF aluminum covers all cases of bypassing the adjust terminal. With no adjust pin bypassing, smaller values of capacitors provide equally good results. Normally, capacitor values on the order of several hundred microfarads are used on the output of the regulators to ensure good transient response with heavy load current changes. Output capacitance can increase without limit and larger values of output capacitance further improve the stability and transient response of the LT1585A/ LT1585A-3.3. Large load current changes are exactly the situation presented by modern microprocessors. The load current step contains higher order frequency components that the output decoupling network must handle until the regulator throttles to the load current level. Capacitors are not ideal elements and contain parasitic resistance and inductance. These parasitic elements dominate the change in output voltage at the beginning of a transient load step change. The ESR of the output capacitors produces an instantaneous step in output voltage (∆V = ∆I • ESR). The ESL of the output capacitors produces a droop proportional to the rate of change of output current (V = L • ∆I/∆t). The output capacitance produces a change in output voltage proportional to the time until the regulator can respond (∆V = ∆t • ∆I/C). These transient effects are illustrated in Figure 1. The use of capacitors with low ESR, low ESL and good high frequency characteristics is critical in meeting the output voltage tolerances of these high speed micropro- 6 ESR EFFECTS ESL EFFECTS CAPACITANCE EFFECTS LT1585A • F01 SLOPE, V ∆I = t C POINT AT WHICH REGULATOR TAKES CONTROL Figure 1 cessors. These requirements dictate a combination of high quality, surface mount tantalum capacitors and ceramic capacitors. The location of the decoupling network is critical to transient response performance. Place the decoupling network as close as possible to the processor pins because trace runs from the decoupling capacitors to the processor pins are inductive. The ideal location for the decoupling network is actually inside the microprocessor socket cavity. In addition, use large power and ground plane areas to minimize distribution drops. A possible stability problem that occurs in monolithic linear regulators is current limit oscillations. The LT1585A/ LT1585A-3.3 essentially have a flat current limit over the range of input supply voltage. The lower current limit rating and 7V maximum supply voltage rating for these devices permit this characteristic. Current limit oscillations are typically nonexistent, unless the input and output decoupling capacitors for the regulators are mounted several inches from the terminals. Protection Diodes In normal operation, the LT1585A/LT1585A-3.3 do not require any protection diodes. Older 3-terminal regulators require protection diodes between the output pin and the input pin or between the adjust pin and the output pin to prevent die overstress. On the adjustable LT1585A, 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. LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION A protection diode between the input and output pins is usually not needed. An internal diode between the input and output pins on the LT1585A/LT1585A-3.3 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 1000µF to 5000µF, and with the input pin instantaneously shorted to ground can damage occur. A crowbar circuit at the input of the LT1585A/LT1585A-3.3 can generate those levels of current, and a diode from output to input is then recommended. This is shown in Figure 2. 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-tooutput voltage differential causes the internal transistors to break down and none of the protection circuitry is then functional. D1 1N4002 (OPTIONAL) VIN + LT1585A-3.3 IN OUT C1 10µF GND + VOUT C2 10µF D1 1N4002 (OPTIONAL) VIN + IN C1 10µF CADJ Output Voltage The LT1585A adjustable regulator develops a 1.25V reference voltage between the output pin and the adjust pin (see Figure 3). 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 55µA. Its output voltage contribution is small and only needs consideration when very precise output voltage setting is required. + IN LT1585A OUT C1 10µF ADJ + VREF R1 VOUT C2 10µF IADJ 55µA R1 + The typical curve for ripple rejection reflects values for the LT1585A-3.3 fixed output voltage part. In applications that require improved ripple rejection, use the adjustable device. A bypass capacitor from the adjust pin 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 100Ω to 120Ω) in the feedback divider network in Figure 2. Therefore, the value of the required adjust pin capacitor is a function of the input ripple frequency. For example, if R1 equals 100Ω and the ripple frequency equals 120Hz, the adjust pin capacitor should be 22µF. At 10kHz, only 0.22µF is needed. VIN LT1585A OUT ADJ Ripple Rejection + VOUT VOUT = VREF (1 + R2/R1) + IADJ (R2) R2 C2 10µF LT1585A • F03 Figure 3. Basic Adjustable Regulator R2 LT1585A • F02 Figure 2 7 LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION Load Regulation load regulation is obtained when the top of resistor divider R1 connects directly to the regulator output and not to the load. Figure 5 illustrates this point. If R1 connects to the load, the effective resistance between the regulator and the load is: It is not possible to provide true remote load sensing because the LT1585A/LT1585A-3.3 are 3-terminal devices. Load regulation is limited by the resistance of the wire connecting the regulators to the load. Load regulation per the data sheet specification is measured at the bottom of the package. RP(1 + R2/R1), RP = Parasitic Line Resistance The connection shown in Figure 5 does not multiply RP by the divider ratio. As an example, RP is about four milliohms per foot with 16-gauge wire. This translates to 4mV per foot at 1A load current. At higher load currents, this drop represents a significant percentage of the overall regulation. It is important to keep the positive lead between the regulator and the load as short as possible and to use large wire or PC board traces. For fixed voltage devices, negative side sensing is a true Kelvin connection with the ground pin of the device returned to the negative side of the load. This is illustrated in Figure 4. For adjustable voltage devices, negative side sensing is a true Kelvin connection with the bottom of the output divider returned to the negative side of the load. The best VIN LT1585A-3.3 IN OUT RP PARASITIC LINE RESISTANCE GND RL LT1585A • F04 Figure 4. Connection for Best Load Regulation RP PARASITIC LINE RESISTANCE LT1585A VIN IN OUT ADJ R1* RL R2* *CONNECT R1 TO CASE CONNECT R2 TO LOAD LT1585A • F05 Figure 5. Connection for Best Load Regulation 8 LT1585A/LT1585A-3.3 U W U U APPLICATIONS INFORMATION Thermal Considerations The LT1585A/LT1585A-3.3 family protects the device 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-to-ambient. These sources include the junction-to-case resistance, the caseto-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. Older regulators, with a single junction-to-case thermal resistance specification, use an average of the two values provided here and allow excessive junction temperatures under certain conditions of ambient temperature and heat sink resistance. Calculate the maximum junction temperature for both sections to ensure that both thermal limits are met. 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. Linear Technology strongly recommends thermal compound at the case-to-heat sink interface. Use a thermally conductive spacer if the case of the device must be electrically isolated and include its contribution to the total thermal resistance. Please consult “Mounting Considerations for Power Semiconduc- tors” 1990 Linear Applications Handbook, Volume I, Pages RR3-1 to RR3-20. The output connects to the case of both the LT1585A and the LT1585A-3.3. For example, using an LT1585ACT-3.3 (TO-220, commercial) and assuming: VIN(Max Continuous) = 5.25V (5V + 5%), VOUT = 3.3V, IOUT = 5A TA = 70°C, θHEAT SINK = 3°C/W θCASE-TO-HEAT SINK = 1°C/W (with Thermal Compound) Power dissipation under these conditions is equal to: PD = (VIN – VOUT)(IOUT) = (5.25 – 3.3)(5) = 9.75W Junction temperature will be equal to: TJ = TA + PD(θHEAT SINK + θCASE-TO-HEAT SINK + θJC) For the Control Section: TJ = 70°C + 9.75W (3°C/W + 1°C/W + 0.7°C/W) = 115.8°C 115.8°C < 125°C = TJMAX (Control Section Commercial range) For the Power Transistor: TJ = 70°C + 9.75W (3°C/W + 1°C/W + 3°C/W) = 138.3°C 138.3°C < 150°C = TJMAX (Power Transistor Commercial Range) In both cases the junction temperature is below the maximum rating for the respective sections, ensuring reliable operation. 9 LT1585A/LT1585A-3.3 U TYPICAL APPLICATIONS N Minimum Parts Count LT1585A Adjustable Circuit for the Intel 120MHz Pentium Processor THERMALLOY 7020B-MT 4.75V TO 5.25V IN C1 TO C3 220µF 10V AVX TPS 3 EACH + 3.50V 5A OUT LT1585ACT ADJ C4 330nF 16V AVX X7R 0805 PLACE IN MICROPROCESSOR SOCKET CAVITY R1 110Ω 0.1% R2 197Ω 0.1% + C5 TO C10 100µF 10V AVX TPS 4 EACH LT1585A TA04 AVX CORP. (803) 448-9411 THERMALLOY INC. (214) 243-4321 DO NOT SUBSTITUTE COMPONENTS. LT1585A Transient Response for 3.8A Load Current Step* VOUT 50mV/DIV IOUT 2A/DIV 100µs/DIV LT1584A • TA05 *TRANSIENT RESPONSE MEASURED WITH AN INTEL POWER VALIDATOR. VOUT IS MEASURED AT THE POWER VALIDATOR 10 C11 TO C20 1µF 16V AVX Y5V 0805 24 EACH LT1585A/LT1585A-3.3 U TYPICAL APPLICATIONS N Guaranteed LT1585A Circuit for the Intel 100MHz and Higher Frequency Pentium Processors (Meets Intel Specifications with Worst-Case Tolerances) THERMALLOY 7021B-MT 5V SEE NOTE 5 3 C2 TO C4 + 220µF IN OUT PLACE IN MICROPROCESSOR SOCKET CAVITY 2 SEE NOTE 6 LT1585A 10V AVX TPS 3 EACH + R1 1k ADJ 1 C6 R2 0.01µF 1k C5 33pF NPO C1 0.1µF VOUT R4 2 1 COMP COL 3 + 8 REF V LT1431S 4 7 RM RT SGND FGND 5 6 SENSE R3D 5 R3E 6 83Ω 117Ω SEE NOTE 7 4 R3C 800Ω + C7 100µF 10V 3 R3B 1.35k 2 R3A 1.15k 1 SGND PGND PGND LT1584 • TA06 C8 TO C13 100µF + 10V AVX TPS 4 EACH C14 TO C23 1µF 16V AVX Y5V 0805 24 EACH NOTES: UNLESS OTHERWISE SPECIFIED 1. ALL RESISTOR VALUES ARE OHMS, 1/8W, 5% 2. ALL CAPACITORS ARE 50V, 20% 3. ALL POLARIZED CAPACITORS ARE AVX TYPE TPS OR EQUIVALENT 4. INPUT CAPACITANCE MAY BE REDUCED IF THE 5V SUPPLY IS WELL BYPASSED 5. FOR 100MHz PENTIUM PROCESSOR, INPUT VOLTAGE MUST BE AT LEAST 4.85V AT THE REGULATOR INPUT 6. FOR PENTIUM VRE PROCESSOR, R4 NOT INSTALLED – FOR 3.3V OUTPUT, INSTALL 0Ω JUMPER RESISTOR R4 7. R3A TO R3E ARE B.I. TECHNOLOGY 627V100 LT1585A/LT1431 Transient Response for 3.8A Load Current Step* VOUT 50mV/DIV IOUT 2A/DIV 100µs/DIV LT1584A • TA06 *TRANSIENT RESPONSE MEASURED WITH AN INTEL POWER VALIDATOR. VOUT IS MEASURED AT THE POWER VALIDATOR Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 11 LT1585A/LT1585A-3.3 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. T Package 3-Lead Plastic TO-220 0.147 – 0.155 (3.734 – 3.937) DIA 0.390 – 0.415 (9.906 – 10.541) 0.165 – 0.180 (4.293 – 4.699) 0.045 – 0.055 (1.143 – 1.397) 0.230 – 0.270 (5.842 – 6.858) 0.460 – 0.500 (11.684 – 12.700) 0.570 – 0.620 (14.478 – 15.748) 0.330 – 0.370 (8.382 – 9.398) 0.980 – 1.070 (24.892 – 27.178) 0.520 – 0.570 (13.208 – 14.478) 0.090 – 0.110 (2.286 – 2.794) 0.028 – 0.038 (0.711 – 0.965) 0.218 – 0.252 (5.537 – 6.401) 0.013 – 0.023 (0.330 – 0.584) 0.050 (1.270) TYP 0.095 – 0.115 (2.413 – 2.921) T3 (TO-220) 0595 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1430 High Power Step-Down Switching Regulator 5V to 3.3V at 10A LT1580 7A Very Low Dropout Linear Regulator 0.54V Dropout at 7A, Fixed 2.5VOUT and Adjustable LT1584 7A Low Dropout Fixed and Adjustable Linear Regulators Fast Transient Response for Microprocessor Applications LT1587 3A Low Dropout Fixed and Adjustable Linear Regulators Fast Transient Response for Microprocessor Applications 12 Linear Technology Corporation LT/GP 1095 10K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1995