LIN D O C #: 8586 LX8586-xx/8586A-xx 6A L OW D ROPOUT P OSITIVE R E G U L AT O R S T H E I N F I N I T E P O W E R I O F P N N O VA T I O N DESCRIPTION The LX8586/86A series ICs are low dropout three-terminal regulators with a minimum of 6A output current. Pentium® Processor, Power PCTM , Cyrix® 6x86TM and AMD-K5TM applications requiring fast transient response are ideally suited for this product family. The LX8586A is guaranteed to have < 1.1V at 6A and the LX8586 < 1.3V at 6A dropout voltage, making them ideal to provide well-regulated outputs of 2.5V to 3.6V using a 5V input supply. Fixed versions are also available and specified in the Available Options table below. LX8586 1.5V/6A OUT 1500µF Sanyo 6MV1500GX 121Ω ±1% ADJ ■ ■ ■ ■ ■ ■ ■ GTL+ BUS TERMINATORS PENTIUM PROCESSOR SUPPLIES POWER PC SUPPLIES MICROPROCESSOR SUPPLIES LOW VOLTAGE LOGIC SUPPLIES POST REGULATOR FOR SWITCHING SUPPLY LXE9001 EVALUATION BOARD FOR PENTIUM APPLICATIONS AVAILABLE. CONSULT FACTORY ■ CYRIX 6x86TM ■ AMD-K5TM AND AMD-K6TM To GTL+ Terminator 4x 1500µF Sanyo 6MV1500GX A VA I L A B L E O P T I O N S Part # 24.3Ω ±1% A P P L I C AT I O N OF LX8586 AS H E E T A P P L I C AT I O N S H.S. (Note A) IN S ■ THREE-TERMINAL ADJUSTABLE OR FIXED OUTPUT ■ GUARANTEED < 1.1V HEADROOM AT 6A (LX8586A) ■ GUARANTEED < 1.3V HEADROOM AT 6A (LX8586) ■ OUTPUT CURRENT OF 6A MINIMUM p FAST TRANSIENT RESPONSE p 1% VOLTAGE REFERENCE INITIAL ACCURACY p OUTPUT SHORT CIRCUIT PROTECTION p BUILT-IN THERMAL SHUTDOWN ■ EVALUATION BOARD AVAILABLE: REQUEST LXE9001 EVALUATION KIT Current limit is trimmed above 6.1A to ensure adequate output current and controlled short-circuit current. On-chip thermal limiting provides protection against any combination of overload that would create excessive junction temperatures. The LX8586/86A series devices are available in both through-hole versions of the industry-standard, 3-pin TO-220 and TO-247 power packages. Along with the standard µP supply applications, the LX8586 series of products are ideal for Pentium® Pro Processor applications such as GTL+ Bus terminators (see application below). 1.5V, 6A R E G U L AT O R 3.3V A T A K E Y F E AT U R E S PRODUCT HIGHLIGHT From Silverbox Power Supply D R O D U C T I O N PER PAR T # Output Voltage LX8586/86A-00 Adjustable LX8586/86A-33 3.3V Other voltage options may be available — Please contact factory for details. 1 . 5 V G T L + B U S T E R M I N AT O R Note A: See application note, page 3. PA C K A G E O R D E R I N F O R M AT I O N TO-220 TO-247 Dropout TA (°C) P Plastic V Plastic Voltage 3-pin 3-terminal 0 to 125 1.3V LX8586-xxCP LX8586-xxCV 1.1V LX8586A-xxCP LX8586A-xxCV "xx" refers to output voltage, please see table above. F O R F U R T H E R I N F O R M AT I O N C A L L ( 7 1 4 ) 8 9 8 - 8 1 2 1 Copyright © 1996 Rev. 1.0 12/96 11861 WESTERN A VENUE , G ARDEN G ROVE , CA. 92841 1 PRODUCT DATABOOK 1996/1997 LX8586-xx/8586A-xx 6 A L O W D R O P O U T P O S I T I V E R E G U L AT O R S P R O D U C T I O N A B S O L U T E M A X I M U M R AT I N G S D A T A S H E E T PACKAGE PIN OUTS (Note 1) Power Dissipation .................................................................................. Internally Limited Input Voltage ................................................................................................................ 10V Input to Output Voltage Differential ........................................................................... 10V Operating Junction Temperature Plastic (P Package) ................................................................................................ 150°C Storage Temperature Range ...................................................................... -65°C to 150°C Lead Temperature (Soldering, 10 seconds) ............................................................. 300°C Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal. T H E R MAL DATA TAB IS VOUT 3 VIN VOUT ADJ / GND* 2 1 P PACKAGE (Top View) * Pin 1 is GND for fixed voltage versions. TAB ON REVERSE SIDE IS V OUT P PACKAGE: THERMAL RESISTANCE-JUNCTION TO TAB, θJT 2.7°C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ JA 60°C/W 3 2 1 VIN VOUT ADJ / GND* V PACKAGE: THERMAL RESISTANCE-JUNCTION TO TAB, θJT 1.6°C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ JA 35°C/W V PACKAGE (Top View) * Pin 1 is GND for fixed voltage versions. Junction Temperature Calculation: TJ = TA + (PD x θJA). The θ JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. 2 Copyright © 1996 Rev. 1.0 12/96 PRODUCT DATABOOK 1996/1997 LX8586-xx/8586A-xx 6A L OW D ROPOUT P OSITIVE R E G U L AT O R S P R O D U C T I O N D A T A S H E E T ELECTRICAL CHARACTERISTICS (Unless otherwise specified, these specifications apply over the operating ambient temperatures for the LX8586-xx/8586A-xx with 0°C ≤ TA ≤ 125°C; VIN - VOUT = 3V; IOUT = 6A. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature.) LX8586-00/86A-00 (Adjustable) Parameter Reference Voltage Symbol Test Conditions VREF IOUT = 10mA, TA = 25°C 10mA ≤ IOUT ≤ 6A, 1.5V ≤ (VIN - VOUT), VIN ≤ 7V, P ≤ PMAX Line Regulation (Note 2) ∆VREF (VIN) IOUT = 10mA, 1.5V ≤ (VIN - VOUT ), VIN ≤ 7V Load Regulation (Note 2) ∆VREF (IOUT) VIN - V OUT = 3V, 10mA ≤ IOUT ≤ 6A ∆VOUT (Pwr) TA = 25°C, 20ms pulse Thermal Regulation Ripple Rejection (Note 3) VOUT = 3.3V, f =120Hz, COUT = 100µf Tantalum, VIN = 5V CADJ = 10µF, TA = 25°C, IOUT = 6A Adjust Pin Current I ADJ Adjust Pin Current Change ∆IADJ 10mA ≤ IOUT ≤ 6A, 1.5V ≤ (VIN - VOUT), VIN ≤ 7V Dropout Voltage LX8586-00 ∆V ∆VREF = 1%, IOUT = 6A LX8586A-00 ∆VREF = 1%, IOUT = 6A Minimum Load Current IOUT(MIN) VIN ≤ 7V Maximum Output Current IOUT(MAX) 1.4V ≤ (V IN - VOUT), VIN ≤ 7V Temperature Stability ∆VOUT (T) Long Term Stability ∆VOUT (t) TA = 125°C, 1000 hrs VOUT (RMS) TA = 25°C, 10Hz ≤ f ≤ 10kHz RMS Output Noise (% of VOUT) LX8586/86A-00 Min. Typ. Max. 1.238 1.225 60 6.1 Units 1.250 1.250 0.035 0.1 0.01 83 1.262 1.275 0.2 0.5 0.02 V V % % %/W dB 55 0.2 1.1 0.9 2 8 0.25 0.3 0.003 100 5 1.3 1.1 10 µA µA V V mA A % % % 1 LX8586-33/86A-33 (3.3V Fixed) Parameter Output Voltage Symbol VOUT Test Conditions VIN = 5V, IOUT = 0mA, TA = 25°C 4.75V ≤ V IN ≤ 10V, 0mA ≤ IOUT ≤ 6A, P ≤ PMAX Line Regulation (Note 2) ∆VOUT 4.75V ≤ V IN ≤ 7V (VIN ) 4.75V ≤ VIN ≤ 10V Load Regulation (Note 2) ∆VOUT (IOUT) VIN = 5V, 10mA ≤ IOUT ≤ IOUT (MAX) Thermal Regulation (Note 3) ∆VOUT (Pwr) TA = 25°C, 20ms pulse Ripple Rejection (Note 3) COUT = 100µF (Tantalum), IOUT = 6A, TA = 25°C Quiescent Current IQ 0mA ≤ IOUT ≤ IOUT (MAX) , 4.75V ≤ VIN ≤ 10V Dropout Voltage LX8586-33 ∆V ∆VOUT = 1%, IOUT ≤ IOUT (MAX) LX8586A-33 ∆VOUT = 1%, IOUT ≤ IOUT (MAX) Maximum Output Current IOUT (MAX) VIN ≤ 7A Temperature Stability (Note 3) ∆VOUT (T) Long Term Stability (Note 3) ∆VOUT (t) TA = 125°C, 1000 hours RMS Output Noise (% of VOUT) (Note 3) VOUT (RMS) TA = 25°C, 10Hz ≤ f ≤ 10kHz LX8586-33/86A-33 Min. Typ. Max. 3.267 3.235 65 6.1 3.3 3.3 1 2 5 0.01 83 4 1.1 0.9 8 0.25 0.3 0.003 3.333 3.365 6 10 15 0.02 10 1.3 1.1 1 Units V V mV mV mV %/W dB mA V V A % % % Note 2. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are covered under the specification for thermal regulation. Note 3. These parameters, although guaranteed, are not tested in production. Copyright © 1996 Rev. 1.0 12/96 3 PRODUCT DATABOOK 1996/1997 LX8586-xx/8586A-xx 6 A L O W D R O P O U T P O S I T I V E R E G U L AT O R S P R O D U C T I O N D A T A S H E E T A P P L I C AT I O N N O T E S The LX8586/86A series ICs are easy to use Low-Dropout (LDO) voltage regulators. They have all of the standard self-protection features expected of a voltage regulator: short circuit protection, safe operating area protection and automatic thermal shutdown if the device temperature rises above approximately 165°C. Use of an output capacitor is REQUIRED with the LX8586/86A series. Please see the table below for recommended minimum capacitor values. These regulators offer a more tightly controlled reference voltage tolerance and superior reference stability when measured against the older pin-compatible regulator types that they replace. STABILITY The output capacitor is part of the regulator’s frequency compensation system. Many types of capacitors are available, with different capacitance value tolerances, capacitance temperature coefficients, and equivalent series impedances. For all operating conditions, connection of a 220µF aluminum electrolytic capacitor or a 47µF solid tantalum capacitor between the output terminal and ground will guarantee stable operation. If a bypass capacitor is connected between the output voltage adjust (ADJ) pin and ground, ripple rejection will be improved (please see the section entitled “RIPPLE REJECTION”). When ADJ pin bypassing is used, the required output capacitor value increases. Output capacitor values of 220µF (aluminum) or 47µF (tantalum) provide for all cases of bypassing the ADJ pin. If an ADJ pin bypass capacitor is not used, smaller output capacitor values are adequate. The table below shows recommended minimum capacitance values for stable operation. RECOMMENDED CAPACITOR VALUES INPUT OUTPUT ADJ 10µF 10µF 15µF Tantalum, 100µF Aluminum 47µF Tantalum, 220µF Aluminum None 15µF In order to ensure good transient response from the power supply system under rapidly changing current load conditions, designers generally use several output capacitors connected in parallel. Such an arrangement serves to minimize the effects of the parasitic resistance (ESR) and inductance (ESL) that are present in all capacitors. Cost-effective solutions that sufficiently limit ESR and ESL effects generally result in total capacitance values in the range of hundreds to thousands of microfarads, which is more than adequate to meet regulator output capacitor specifications. Output capacitance values may be increased without limit. The circuit shown in Figure 1 can be used to observe the transient response characteristics of the regulator in a power system under changing loads. The effects of different capacitor types and values on transient response parameters, such as overshoot and undershoot, can be quickly compared in order to develop an optimum solution. 4 Power Supply IN LX8586/86A OUT ADJ Minumum Load (Larger resistor) Full Load (Smaller resistor) RDSON << RL Star Ground 10ms 1 sec FIGURE 1 — DYNAMIC INPUT and OUTPUT TEST OVERLOAD RECOVERY Like almost all IC power regulators, the LX8586/86A regulators are equipped with Safe Operating Area (SOA) protection. The SOA circuit limits the regulator's maximum output current to progressively lower values as the input-to-output voltage difference increases. By limiting the maximum output current, the SOA circuit keeps the amount of power that is dissipated in the regulator itself within safe limits for all values of input-to-output voltage within the operating range of the regulator. The LX8586/86A SOA protection system is designed to be able to supply some output current for all values of input-to-output voltage, up to the device breakdown voltage. Under some conditions, a correctly operating SOA circuit may prevent a power supply system from returning to regulated operation after removal of an intermittent short circuit at the output of the regulator. This is a normal mode of operation which can be seen in most similar products, including older devices such as 7800 series regulators. It is most likely to occur when the power system input voltage is relatively high and the load impedance is relatively low. When the power system is started “cold”, both the input and output voltages are very close to zero. The output voltage closely follows the rising input voltage, and the input-to-output voltage difference is small. The SOA circuit therefore permits the regulator to supply large amounts of current as needed to develop the designed voltage level at the regulator output. Now consider the case where the regulator is supplying regulated voltage to a resistive load under steady state conditions. A moderate input-to-output voltage appears across the regulator but the voltage difference is small enough that the SOA circuitry allows sufficient current to flow through the regulator to develop the designed output voltage across the load resistance. If the output resistor is short-circuited to ground, the input-to-output voltage difference across the regulator suddenly becomes larger by the amount of voltage that had appeared across the load resistor. The SOA circuit reads the increased input-tooutput voltage, and cuts back the amount of current that it will permit the regulator to supply to its output terminal. When the short circuit across the output resistor is removed, all the regulator output current will again flow through the output resistor. The maximum current that the regulator can supply to the resistor will be limited by the SOA circuit, based on the large input-to-output voltage across the regulator at the time the short circuit is removed from the output. Copyright © 1996 Rev. 1.0 12/96 PRODUCT DATABOOK 1996/1997 LX8586-xx/8586A-xx 6A L OW D ROPOUT P OSITIVE R E G U L AT O R S P R O D U C T I O N D A T A S H E E T A P P L I C AT I O N N O T E S OVERLOAD RECOVERY (continued) If this limited current is not sufficient to develop the designed voltage across the output resistor, the voltage will stabilize at some lower value, and will never reach the designed value. Under these circumstances, it may be necessary to cycle the input voltage down to zero in order to make the regulator output voltage return to regulation. LX8586/86A C = 1 / (6.28 * FR * R1) ≡ the value of the capacitor in Farads; select an equal or larger standard value. FR ≡ the ripple frequency in Hz R1 ≡ the value of resistor R1 in ohms where: C At a ripple frequency of 120Hz, with R1 = 100Ω: C = 1 / (6.28 * 120Hz * 100Ω) = 13.3µF The closest equal or larger standard value should be used, in this case, 15µF. When an ADJ pin bypass capacitor is used, output ripple amplitude will be essentially independent of the output voltage. If an ADJ pin bypass capacitor is not used, output ripple will be proportional to the ratio of the output voltage to the reference voltage: M = VOUT/VREF where: M VREF ≡ a multiplier for the ripple seen when the ADJ pin is optimally bypassed. = 1.25V. For example, if VOUT = 2.5V the output ripple will be: M = 2.5V/1.25V= 2 VOUT ADJ VREF VOUT = VREF 1 + R2 + IADJ R2 R1 LOAD REGULATION Because the LX8586/86A regulators are three-terminal devices, it is not possible to provide true remote load sensing. Load regulation will be limited by the resistance of the wire connecting the regulator to the load. The data sheet specification for load regulation is measured at the bottom of the package. Negative side sensing is a true Kelvin connection, with the bottom of the output divider returned to the negative side of the load. Although it may not be immediately obvious, best load regulation is obtained when the top of the resistor divider, (R1), is connected directly to the case of the regulator, not to the load. This is illustrated in Figure 3. If R1 were connected to the load, the effective resistance between the regulator and the load would be: RPeff = RP * R2+R1 R1 where: RP ≡ Actual parasitic line resistance. When the circuit is connected as shown in Figure 3, the parasitic resistance appears as its actual value, rather than the higher RPeff. LX8586/86A VIN OUT IN ADJ RP Parasitic Line Resistance Connect R1 to Case of Regulator R1 OUTPUT VOLTAGE R2 Copyright © 1996 Rev. 1.0 12/96 R2 FIGURE 2 — BASIC ADJUSTABLE REGULATOR Output ripple will be twice as bad as it would be if the ADJ pin were to be bypassed to ground with a properly selected capacitor. The LX8586/86A ICs develop a 1.25V reference voltage between the output and the adjust terminal (See Figure 2). By placing a resistor, R1, between these two terminals, a constant current is caused 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. Because IADJ is very small and constant when compared with the current through R1, it represents a small error and can usually be ignored. R1 IADJ 50µA RIPPLE REJECTION Ripple rejection can be improved by connecting a capacitor between the ADJ pin and ground. The value of the capacitor should be chosen so that the impedance of the capacitor is equal in magnitude to the resistance of R1 at the ripple frequency. The capacitor value can be determined by using this equation: OUT IN VIN RL Connect R2 to Load FIGURE 3 — CONNECTIONS FOR BEST LOAD REGULATION 5 PRODUCT DATABOOK 1996/1997 LX8586-xx/8586A-xx 6 A L O W D R O P O U T P O S I T I V E R E G U L AT O R S P R O D U C T I O N D A T A S H E E T A P P L I C AT I O N N O T E S LOAD REGULATION (continued) Even when the circuit is optimally configured, parasitic resistance can be a significant source of error. A 100 mil wide PC trace built from 1 oz. copper-clad circuit board material has a parasitic resistance of about 5 milliohms per inch of its length at room temperature. If a 3-terminal regulator used to supply 2.50 volts is connected by 2 inches of this trace to a load which draws 5 amps of current, a 50 millivolt drop will appear between the regulator and the load. Even when the regulator output voltage is precisely 2.50 volts, the load will only see 2.45 volts, which is a 2% error. It is important to keep the connection between the regulator output pin and the load as short as possible, and to use wide traces or heavy-gauge wire. The minimum specified output capacitance for the regulator should be located near the reglator package. If several capacitors are used in parallel to construct the power system output capacitance, any capacitors beyond the minimum needed to meet the specified requirements of the regulator should be located near the sections of the load that require rapidly-changing amounts of current. Placing capacitors near the sources of load transients will help ensure that power system transient response is not impaired by the effects of trace impedance. To maintain good load regulation, wide traces should be used on the input side of the regulator, especially between the input capacitors and the regulator. Input capacitor ESR must be small enough that the voltage at the input pin does not drop below VIN (MIN) during transients. can be used, as long as its added contribution to thermal resistance is considered. Note that the case of all devices in this series is electrically connected to the output. Example Given: VIN = 5V VOUT = 2.8V, IOUT = 5.0A Ambient Temp., TA = 50°C RθJT = 2.7°C/W for TO-220 300 ft/min airflow available Find: Proper Heat Sink to keep IC's junction temperature below 125°C.** Solution: The junction temperature is: TJ = PD (RθJT + RθCS + R θSA) + TA where: PD ≡ Dissipated power. RθJT ≡ Thermal resistance from the junction to the mounting tab of the package. RθCS ≡ Thermal resistance through the interface between the IC and the surface on which it is mounted. (1.0°C/W at 6 in-lbs mounting screw torque.) RθSA ≡ Thermal resistance from the mounting surface to ambient (thermal resistance of the heat sink). TS ≡ Heat sink temperature. TJ VIN (MIN) = VOUT + VDROPOUT (MAX) ≡ the lowest allowable instantaneous voltage at the input pin. ≡ the designed output voltage for the VOUT power supply system. VDROPOUT (MAX) ≡ the specified dropout voltage for the installed regulator. where: VIN (MIN) THERMAL CONSIDERATIONS The LX8586/86A regulators have internal power and thermal limiting circuitry designed to protect each device under overload conditions. For continuous normal load conditions, however, maximum junction temperature ratings must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. This includes junction to case, case to heat sink interface, and heat sink thermal resistance itself. Junction-to-case thermal resistance is specified from the IC junction to the back surface of the case directly opposite the die. This is the lowest resistance path for heat flow. Proper mounting is required to ensure the best possible thermal flow from this area of the package to the heat sink. Thermal compound at the case-toheat-sink interface is strongly recommended. If the case of the device must be electrically isolated, a thermally conductive spacer 6 TC RθJT TS RθCS TA RθSA First, find the maximum allowable thermal resistance of the heat sink: TJ - TA - (RθJT + R θCS ) RθSA = PD 5.0A PD = (VIN(MAX) - VOUT) I OUT = (5.0V-2.8V) * RθSA 125°C - 50°C = 11.0W (5.0V-2.8V) * 5.0A = - (2.7°C/W + 1.0°C/W) = 3.1°C/W Next, select a suitable heat sink. The selected heat sink must have RθSA ≤ 3.1°C/W. Thermalloy heatsink 6296B has RθSA = 3.0°C/W with 300ft/min air flow. Finally, verify that junction temperature remains within specification using the selected heat sink: TJ = 11W (2.7°C/W + 1.0°C/W + 3.0°C/W) + 50°C = 124°C ** Although the device can operate up to 150°C junction, it is recommended for long term reliability to keep the junction temperature below 125°C whenever possible. Copyright © 1996 Rev. 1.0 12/96 PRODUCT DATABOOK 1996/1997 LX8586-xx/8586A-xx 6A L OW D ROPOUT P OSITIVE R E G U L AT O R S P R O D U C T I O N D S A T A H E E T T Y P I C A L A P P L I C AT I O N S (Note A) VIN 10µF LX8586/86A LX8586/86A 5V OUT IN * C1 improves ripple rejection. XC should be ≈ R1 at ripple frequency. VOUT R1 121Ω 1% ADJ R2 365Ω 1% VIN OUT IN (Note A) ADJ C1* 10µF 150µF VOUT** R1 121Ω R2 1k C1 10µF* C2 100µF * Needed if device is far from filter capacitors. ** VOUT = 1.25V 1 + R2 R1 FIGURE 4 — IMPROVING RIPPLE REJECTION FIGURE 5 — 1.2V - 8V ADJUSTABLE REGULATOR LX8586/86A VIN OUT IN (Note A) ADJ 5V 121Ω 1% 100µF 10µF 1k TTL Output 2N3904 1k 365Ω 1% FIGURE 6 — 5V REGULATOR WITH SHUTDOWN LX8586-33/86A-33 VIN OUT IN GND 10µF Tantalum or 100µF Aluminum 3.3V Min. 15µF Tantalum or 100µF Aluminum capacitor. May be increased without limit. ESR must be less than 50mΩ. FIGURE 7 — FIXED 3.3V OUTPUT REGULATOR Note A: VIN (MIN) = (Intended VOUT) + (VDROPOUT (MAX)) Pentium is a registered trademark of Intel Corporation. Cyrix is a registered trademark and 6x86 is a trademark of Cyrix Corporation. K5 and K6 are trademarks of AMD. Power PC is a trademark of International Business Machines Corporation. Copyright © 1996 Rev. 1.0 12/96 7