LX8415-xx 0.5A LOW DROPOUT POSITIVE REGULATORS T H E I N F I N I T E P O W E R O F I P N N O V A T I O N R E L I M I N A R Y A T A S H E E T KEY FEATURES 0.7% Line Regulation Maximum 0.7% Load Regulation Maximum Output Current Of 500mA Regulates To <1.3V Dropout Space Saving SOT-223 Surface Mount Package Guaranteed Dropout Voltage At Multiple Current Levels 3-Terminal Adjustable, Fixed 2.5V And Fixed 3.3V bs ol et e DESCRIPTION The LX8415 series ICs are positive Low to minimize stress on both the regulator and Dropout (LDO) regulators. At the designed the system power source when they are maximum load current, the LX8415 series operated under short-circuit conditions. The dropout voltage is guaranteed to be 1.3V or regulator's internal circuitry will operate at lower at 0.5A. The dropout voltage decreases input-to-output differential voltages down to with load current. 1V. The LX8415 is available in an adjustable Most regulator circuit designs include output voltage version and fixed output output capacitors with values in the range of versions of 2.5V and 3.3V. On chip trimming tens to hundreds of microfarads or more. The of the internal voltage reference allows LX8415 typically requires at least 10µF of specification of the initial output voltage to output capacitance for stable operation. within ±1% of its nominal value. The output The LX8415 is available in the low profile current limit point is also trimmed, which plastic SOT-223 package for applications helps where space is at a premium. D IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com KEY FEATURES Battery Chargers 5V To 3.3V Linear Regulators Post Regulators For Switching Supplies Modems DVD Players Available Options Per Part # PRODUCT HIGHLIGHT Part # LX8415-25 LX8415-33 LX8415-00 Low Cost 5V to 3.3V Regulator LX8415-xx VIN 5V IN VOUT 3.3V OUT ADJ 10µF Output Voltage 2.5V 3.3V Adjustable R1 60.4 Ω 22µF O R2 100Ω PACKAGE ORDER INFO Plastic SOT-223 ST 3-Pin TA (°C) RoHS Compliant / Pb-free Transition DC: 0522 0 to 125 LX8415-xxCST Note: Available in Tape & Reel. Append the letter “TR” to the part number. (i.e. LX8415-25CST-TR) Copyright © 1999 Rev. 0.5,2005-06-16 MICROSEMI INC. 11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570 1 PRODUCT DATABOOK 1996/1997 LX8415-xx 0 . 5 A L O W D ROPOUT P OSITIVE R EGULATORS P R E L I M I N A R Y A B S O LUT E M AXIM UM R ATINGS D A T A S H E E T PACKAGE PIN OUTS (Note 1) Power Dissipation .................................................................................. Internally Limited Input Voltage LX8415-00 (Adjustable) / 8415-33 (3.3V) .................................................................. 7V Surge Voltage ................................................................................................................. 7V Operating Junction Temperature Plastic (ST, DD & DT Packages) .......................................................................... 150°C Storage Temperature Range ...................................................................... -65°C to 150°C Lead Temperature (Soldering, 10 seconds) ............................................................. 300°C Short-Circuit Protection ....................................................................................... Indefinite TAB IS V OUT 3. IN 2. OUT 1. ADJ / GND bs ol et e ST PACKAGE (Top View) RoHS Peak Package Solder Reflow Temp. (40 seconds max. exposure)............................. 260°C (+0, -5) RoHS / Pb-free 100% Matte Tin Lead Finish 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 ST PACKAGE: THERMAL RESISTANCE-JUNCTION TO TAB, θJT 15°C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, θ JA *150°C/W Junction Temperature Calculation: TJ = TA + (PD x θJA). The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. * θ JAcan be improved with package soldered to 0.5IN2 copper area over backside ground plane or internal power plane. θJAcan vary from 20ºC/W to > 40ºC/W depending on mounting technique. (See Application Notes Section: Thermal Considerations) BLOCK D IA GR A M VIN Bias Circuit Bandgap Circuit Control Circuit Output Circuit O Thermal Limit Circuit ADJ 2 VOUT Current Limit Circuit Copyright © 1999 Rev. 0.5 PRODUCT DATABOOK 1996/1997 LX8415-xx 0 . 5 A L O W D ROPOUT P OSITIVE REGULATORS P R E L I M I N A R Y D A T A S H E E T R E C O M M E N D E D O P E R AT I N G C O N D I T I O N S Parameter Symbol (Note 2) Recommended Operating Conditions Min. Typ. Max. Input Voltage Operating Voltage LX8415-xx Operating Ambient Temperature Range Units 7 125 0 V °C Note 2. Range over which the device is functional. bs ol et e ELECTRICAL CHARACTERISTICS (Unless otherwise specified: 0°C ≤ TJ ≤ 125°C, IMAX = 0.5A for the LX8415-xx.) Parameter Symbol Reference Voltage LX8415-00 Output Voltage LX8415-25 LX8415-33 Line Regulation (Note 3) Load Regulation (Note 3) Dropout Voltage (Note 4) LX8415-00 LX8415-25 / 33 LX8415-00 LX8415-25 / 33 LX8415-xx VREF Test Conditions IOUT = 10mA, (VIN - VOUT) = 2V, TJ = 25°C 10mA ≤ IOUT ≤ IMAX, 1.5V ≤ (VIN - VOUT) ≤ 6V IOUT = 10mA, VIN = 5V, TJ = 25°C 0mA ≤ IOUT ≤ IMAX, 4.75V ≤ V IN ≤ 6V IOUT = 10mA, VIN = 5V, TJ = 25°C 0mA ≤ IOUT ≤ IMAX, 4.75V ≤ V IN ≤ 6V I OUT = 10mA, 1.5V ≤ VIN - V OUT ≤ 6V I OUT = 0mA, 4.75V ≤ V IN ≤ 6V (V IN - VOUT) = 3V, 10mA ≤ IOUT ≤ IMAX VIN = 4.75V, 0mA ≤ IOUT ≤ IMAX IOUT = 100mA IOUT = 300mA IOUT = IMAX (V IN - VOUT) ≥ 1.3V, T J = 25°C VIN ≤ 6V, (LX8415-00) VIN ≤ 6V TA = 25°C, 30ms Pulse fRIPPLE = 120Hz, (VIN - VOUT ) = 3V, VRIPPLE = 1Vp - p Current Limit LX8415-xx I OUT (MAX) Minimum Load Current (Note 5) Quiescent Current LX8415-25 / 33 Thermal Regulation Ripple Rejection Adjust Pin Current LX8415(A)-00 Adjust Pin Current Change LX8415(A)-00 10mA ≤ IOUT ≤ IMAX, 1.5V ≤ (VIN - VOUT) ≤ 6V Temperature Stability Long Term Stability TA = 125°C, 1000Hrs RMS Output Noise (% of V OUT), 10Hz ≤ f ≤ 10kHz Min. 1.238 1.225 2.475 2.450 3.267 3.235 500 60 LX8415-xx Typ. Max. 1.250 1.250 2.500 2.500 3.300 3.300 0.05 1 0.15 10 1.05 1.10 1.15 950 0.5 4.5 0.08 75 60 0.2 0.5 0.3 0.003 1.262 1.275 2.525 2.550 3.333 3.365 0.7 7 0.5 20 1.20 1.25 1.30 10 10 0.2 130 5 Units V V V V V V % mV % mV V V V mA mA mA %/W dB µA µA % % % O Notes: 3. See thermal regulation specification for changes in output voltage due to heating effects. Load regulation and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. 4. Dropout voltage is specified over the full output current range of the device. Dropout voltage is defined as the minimum input/output differential measured at the specified output current. Test points and limits are also shown on the Dropout Voltage Curve. 5. Minimum load current is defined as the minimum output current required to maintain regulation. Copyright © 1999 Rev. 0.5 3 PRODUCT DATABOOK 1996/1997 LX8415-xx 0 . 5 A L O W D ROPOUT P OSITIVE R EGULATORS P R E L I M I N A R Y D A T A S H E E T A P P L I C AT I O N N O T E S Power Supply IN LX8415-xx OUT Minumum Load (Larger resistor) Full Load (Smaller resistor) ADJ C1 RDSON << RL C2 10ms Star Ground 1 sec bs ol et e The LX8415 series ICs are easy to use Low-Dropout (LDO) voltage regulators. They have the standard self-protection features expected of a voltage regulator: short circuit protection and automatic thermal shutdown if the device temperature rises above approximately 165°C. Use of an output capacitor is REQUIRED with the LX8415 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 O 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 FIGURE 1 — DYNAMIC INPUT and OUTPUT TEST 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: C = 1 / (6.28 * FR * R1) ≡ the value of the capacitor in Farads; select an equal or larger standard value. F R ≡ 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 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. Copyright © 1999 Rev. 0.5 PRODUCT DATABOOK 1996/1997 LX8415-xx 0 . 5 A L O W D ROPOUT P OSITIVE REGULATORS P R E L I M I N A R Y 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) OUTPUT VOLTAGE VIN LX8415-xx OUT IN ADJ IN LX8415-xx OUT ADJ R1 R2 VOUT VREF R1 IADJ 50µA VOUT = VREF 1 + R2 + IADJ R2 R1 Connect R1 to Case of Regulator Connect R2 to Load FIGURE 3 — CONNECTIONS FOR BEST LOAD REGULATION LOAD REGULATION Because the LX8415 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: R2+R1 RPeff = RP * R1 O RL R2 FIGURE 2 — BASIC ADJUSTABLE REGULATOR 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. Even when the circuit is optimally configured, parasitic resistance can be a significant source of error. A 100 mil (2.54 mm) 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 Copyright © 1999 Rev. 0.5 VIN RP Parasitic Line Resistance bs ol et e The LX8415 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. 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. VIN (MIN) = VOUT + VDROPOUT (MAX) where: VIN (MIN) VOUT VDROPOUT (MAX) ≡ the lowest allowable instantaneous voltage at the input pin. ≡ the designed output voltage for the power supply system. ≡ the specified dropout voltage for the installed regulator. THERMAL CONSIDERATIONS The LX8415 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. 5 PRODUCT DATABOOK 1996/1997 LX8415-xx 0 . 5 A L O W D ROPOUT P OSITIVE R EGULATORS P R E L I M I N A R Y D A T A S H E E T A P P L I C AT I O N N O T E S THERMAL CONSIDERATIONS (continued) Example Given: VIN = 5.0V ±5%, VOUT = 2.5V ±3% IOUT = 0.5A, TA = 55°C, TJ = 125°C RθJT = 15°C/W, RθTS = 5°C/W PD = [[VIN * (1 + TolVIN )] - [VOUT * (1 - TolVOUT)]] * IOUT PD = 1.4W RθSA = TJ - TA - (RθJT + R θTS) , PD RθSA = 29.6°C/W bs ol et e Find: The size of a square area of 1oz. copper circuitboard trace-foil that will serve as a heatsink, adequate to maintain the junction temperature of the LX8415 in the ST (SOT-223) package within specified limits. First, find the maximum allowable thermal resistance of the heat sink: 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. RθTS ≡ Thermal resistance through the interface between the IC and the surface on which it is mounted. RθSA ≡ Thermal resistance from the mounting surface of the heatsink to ambient. TS ≡ Heat sink temperature. TJ TC Rq CS TA AreaSINK = 3.1°C/W in 2 R θSA - 22.3°C/W Substituting the value for RθSA calculated above, we find that a square pad with area: AreaSINK = 0.43 in2 (0.66" x 0.66"), 280mm 2 (17 x 17 mm) will be required to maintain the LX8415 junction temperature within specified limits. Rq SA O Rq JT TS A test was conducted to determine the thermal characteristics of 1 oz. copper circuit-board trace material. The following equation describes the observed relationship between the area of a square copper pad, and the thermal resistance from the tab of a SOT-223 package soldered at the center of the pad to ambient. 6 Copyright © 1999 Rev. 0.5 PRODUCT DATABOOK 1996/1997 LX8415-xx 0 . 5 A L O W D ROPOUT P OSITIVE REGULATORS P R E L I M I N A R Y 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 5V R1 121Ω 1% VOUT VIN IN (Note A) LX8415-xx OUT ADJ C1* 10µF 150µF VOUT** R1 121Ω R2 1k C2 100µF bs ol et e 10µF LX8415-xx OUT IN ADJ * C1 improves ripple rejection. XC should be ≈ R1 at ripple frequency. R2 365Ω 1% C1 10µF* * Needed if device is far from filter capacitors. ** VOUT = 1.25V 1 + R2 R1 FIGURE 4 — IMPROVING RIPPLE REJECTION FIGURE 5 — 1.2V - 6V ADJUSTABLE REGULATOR LX8415-33 VIN OUT IN 10µF Tantalum or 100µF Aluminum GND 3.3V Min. 15µF Tantalum or 100µF Aluminum capacitor. May be increased without limit. ESR must be less than 50mΩ. FIGURE 6 — FIXED 3.3V OUTPUT REGULATOR O Note A: VIN (MIN) = (Intended VOUT ) + (VDROPOUT (MAX)) PRELIMINARY DATA - Information contained in this document is pre-production data, and is proprietary to LinFinity. It may not modified in any way without the express written consent of LinFinity. Product referred to herein is offered in sample form only, and Linfinity reserves the right to change or discontinue this proposed product at any time. Copyright © 1999 Rev. 0.5 7