LP2985 Micropower 150 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and micro SMD Packages Designed for Use with Very Low ESR Output Capacitors General Description Features The LP2985 is a 150 mA, fixed-output voltage regulator designed to provide ultra low-dropout and low noise in battery powered applications. Using an optimized VIP™ (Vertically Integrated PNP) process, the LP2985 delivers unequalled performance in all specifications critical to battery-powered designs: Dropout Voltage: Typically 300 mV @ 150 mA load, and 7 mV @ 1 mA load. Ground Pin Current: Typically 850 µA @ 150 mA load, and 75 µA @ 1 mA load. Enhanced Stability: The LP2985 is stable with output capacitor ESR as low as 5 mΩ, which allows the use of ceramic capacitors on the output. Sleep Mode: Less than 1 µA quiescent current when ON/OFF pin is pulled low. Smallest Possible Size: SOT-23 and micro SMD packages use absolute minimum board space. Precision Output: 1% tolerance output voltages available (A grade). Low Noise: By adding a 10 nF bypass capacitor, output noise can be reduced to 30 µV (typical). Multiple voltage options, from 2.5V to 5.0V, are available as standard products. Consult factory for custom voltages. n n n n n n n n n n n n n n Ultra low dropout voltage Guaranteed 150 mA output current Smallest possible size (SOT-23, micro SMD package) Requires minimum external components Stable with low-ESR output capacitor < 1 µA quiescent current when shut down Low ground pin current at all loads Output voltage accuracy 1% (A Grade) High peak current capability Wide supply voltage range (16V max) Low ZOUT: 0.3Ω typical (10 Hz to 1 MHz) Overtemperature/overcurrent protection −40˚C to +125˚C junction temperature range Custom voltages available Applications n n n n Cellular Phone Palmtop/Laptop Computer Personal Digital Assistant (PDA) Camcorder, Personal Stereo, Camera Block Diagram DS100140-1 VIP™ is a trademark of National Semiconductor Corporation. © 2000 National Semiconductor Corporation DS100140 www.national.com LP2985 Micropower 150 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and micro SMD Packages August 2000 LP2985 Basic Application Circuit DS100140-2 *ON/OFF input must be actively terminated. Tie to VIN if this function is not to be used. **Minimum capacitance is shown to ensure stability (may be increased without limit). Ceramic capacitor required for output (see Application Hints). ***Reduces output noise (may be omitted if application is not noise critical). Use ceramic or film type with very low leakage current (see Application Hints). Connection Diagrams 5-Lead Small Outline Package (M5) micro SMD, 5 Bump Package (BPA05) DS100140-3 Top View See NS Package Number MF05A For ordering information see Table 1 DS100140-46 Note: The actual physical placement of the package marking will vary from part to part. The package marking ″X″ will designate the date code and will vary considerably. Package marking does not correlate to device type in any way. Top View See NS Package Number BPA05 www.national.com 2 LP2985 Ordering Information TABLE 1. Package Marking and Ordering Information Output Voltage (V) Grade Package Marking Order Information Supplied as: 5-Lead Small Outline Package (M5) For output voltages ≤ 2.3V, refer to LP2985LV datasheet. 2.5 A LP2985AIM5X-2.5 LAVA 3000 Units on Tape and Reel 2.5 A LP2985AIM5-2.5 LAVA 1000 Units on Tape and Reel 2.5 STD LP2985IM5X-2.5 LAVB 3000 Units on Tape and Reel 2.5 STD LP2985IM5-2.5 LAVB 1000 Units on Tape and Reel 2.6 A LP2985AIM5X-2.6 LCEA 3000 Units on Tape and Reel 2.6 A LP2985AIM5-2.6 LCEA 1000 Units on Tape and Reel 2.6 STD LP2985IM5X-2.6 LCEB 3000 Units on Tape and Reel 2.6 STD LP2985IM5-2.6 LCEB 1000 Units on Tape and Reel 2.7 A LP2985AIM5X-2.7 LALA 3000 Units on Tape and Reel 2.7 A LP2985AIM5-2.7 LALA 1000 Units on Tape and Reel 2.7 STD LP2985IM5X-2.7 LALB 3000 Units on Tape and Reel 2.7 STD LP2985IM5-2.7 LALB 1000 Units on Tape and Reel 2.8 A LP2985AIM5X-2.8 L0KA 3000 Units on Tape and Reel 2.8 A LP2985AIM5-2.8 L0KA 1000 Units on Tape and Reel 2.8 STD LP2985IM5X-2.8 L0KB 3000 Units on Tape and Reel 2.8 STD LP2985IM5-2.8 L0KB 1000 Units on Tape and Reel 2.9 A LP2985AIM5X-2.9 LAXA 3000 Units on Tape and Reel 2.9 A LP2985AIM5-2.9 LAXA 1000 Units on Tape and Reel 2.9 STD LP2985IM5X-2.9 LAXB 3000 Units on Tape and Reel 2.9 STD LP2985IM5-2.9 LAXB 1000 Units on Tape and Reel 3.0 A LP2985AIM5X-3.0 L0OA 3000 Units on Tape and Reel 3.0 A LP2985AIM5-3.0 L0OA 1000 Units on Tape and Reel 3.0 STD LP2985IM5X-3.0 L0OB 3000 Units on Tape and Reel 3.0 STD LP2985IM5-3.0 L0OB 1000 Units on Tape and Reel 3.1 A LP2985AIM5X-3.1 L0PA 3000 Units on Tape and Reel 3.1 A LP2985AIM5-3.1 L0PA 1000 Units on Tape and Reel 3.1 STD LP2985IM5X-3.1 L0PB 3000 Units on Tape and Reel 3.1 STD LP2985IM5-3.1 L0PB 1000 Units on Tape and Reel 3.2 A LP2985AIM5X-3.2 L0QA 3000 Units on Tape and Reel 3.2 A LP2985AIM5-3.2 L0QA 1000 Units on Tape and Reel 3.2 STD LP2985IM5X-3.2 L0QB 3000 Units on Tape and Reel 3.2 STD LP2985IM5-3.2 L0QB 1000 Units on Tape and Reel 3.3 A LP2985AIM5X-3.3 L0RA 3000 Units on Tape and Reel 3.3 A LP2985AIM5-3.3 L0RA 1000 Units on Tape and Reel 3.3 STD LP2985IM5X-3.3 L0RB 3000 Units on Tape and Reel 3.3 STD LP2985IM5-3.3 L0RB 1000 Units on Tape and Reel 3.5 A LP2985AIM5X-3.5 LAIA 3000 Units on Tape and Reel 3.5 A LP2985AIM5-3.5 LAIA 1000 Units on Tape and Reel 3.5 STD LP2985IM5X-3.5 LAIB 3000 Units on Tape and Reel 3.5 STD LP2985IM5-3.5 LAIB 1000 Units on Tape and Reel 3.6 A LP2985AIM5X-3.6 L0SA 3000 Units on Tape and Reel 3.6 A LP2985AIM5-3.6 L0SA 1000 Units on Tape and Reel 3.6 STD LP2985IM5X-3.6 L0SB 3000 Units on Tape and Reel 3.6 STD LP2985IM5-3.6 L0SB 1000 Units on Tape and Reel 3 www.national.com LP2985 Ordering Information (Continued) TABLE 1. Package Marking and Ordering Information (Continued) Output Voltage (V) Grade Package Marking Order Information Supplied as: For output voltages ≤ 2.3V, refer to LP2985LV datasheet. 3.8 A LP2985AIM5X-3.8 L0YA 3000 Units on Tape and Reel 3.8 A LP2985AIM5-3.8 L0YA 1000 Units on Tape and Reel 3.8 STD LP2985IM5X-3.8 L0YB 3000 Units on Tape and Reel 3.8 STD LP2985IM5-3.8 L0YB 1000 Units on Tape and Reel 4.0 A LP2985AIM5X-4.0 L0TA 3000 Units on Tape and Reel 4.0 A LP2985AIM5-4.0 L0TA 1000 Units on Tape and Reel 4.0 STD LP2985IM5X-4.0 L0TB 3000 Units on Tape and Reel 4.0 STD LP2985IM5-4.0 L0TB 1000 Units on Tape and Reel 4.5 A LP2985AIM5X-4.5 LA7A 3000 Units on Tape and Reel 4.5 A LP2985AIM5-4.5 LA7A 1000 Units on Tape and Reel 4.5 STD LP2985IM5X-4.5 LA7B 3000 Units on Tape and Reel 4.5 STD LP2985IM5-4.5 LA7B 1000 Units on Tape and Reel 4.7 A LP2985AIM5X-4.7 LAJA 3000 Units on Tape and Reel 4.7 A LP2985AIM5-4.7 LAJA 1000 Units on Tape and Reel 4.7 STD LP2985IM5X-4.7 LAJB 3000 Units on Tape and Reel 4.7 STD LP2985IM5-4.7 LAJB 1000 Units on Tape and Reel 4.8 A LP2985AIM5X-4.8 LAKA 3000 Units on Tape and Reel 4.8 A LP2985AIM5-4.8 LAKA 1000 Units on Tape and Reel 4.8 STD LP2985IM5X-4.8 LAKB 3000 Units on Tape and Reel 4.8 STD LP2985IM5-4.8 LAKB 1000 Units on Tape and Reel 5.0 A LP2985AIM5X-5.0 L0UA 3000 Units on Tape and Reel 5.0 A LP2985AIM5-5.0 L0UA 1000 Units on Tape and Reel 5.0 STD LP2985IM5X-5.0 L0UB 3000 Units on Tape and Reel 5.0 STD LP2985IM5-5.0 L0UB 1000 Units on Tape and Reel micro SMD, 5 Bump Package (BPA05) 2.4 A LP2985AIBP-2.4 250 Units on Tape and Reel 2.4 A LP2985AIBPX-2.4 3000 Units on Tape and Reel 2.4 STD LP2985IBP-2.4 250 Units on Tape and Reel 2.4 STD LP2985IBPX-2.4 3000 Units on Tape and Reel 2.5 A LP2985AIBP-2.5 250 Units on Tape and Reel 2.5 A LP2985AIBPX-2.5 3000 Units on Tape and Reel 2.5 STD LP2985IBP-2.5 250 Units on Tape and Reel 2.5 STD LP2985IBPX-2.5 3000 Units on Tape and Reel 2.8 A LP2985AIBP-2.8 250 Units on Tape and Reel 2.8 A LP2985AIBPX-2.8 3000 Units on Tape and Reel 2.8 STD LP2985IBP-2.8 250 Units on Tape and Reel 2.8 STD LP2985IBPX-2.8 3000 Units on Tape and Reel 2.9 A LP2985AIBP-2.9 250 Units on Tape and Reel 2.9 A LP2985AIBPX-2.9 3000 Units on Tape and Reel 2.9 STD LP2985IBP-2.9 250 Units on Tape and Reel 2.9 STD LP2985IBPX-2.9 3000 Units on Tape and Reel 3.0 A LP2985AIBP-3.0 250 Units on Tape and Reel 3.0 A LP2985AIBPX-3.0 3000 Units on Tape and Reel 3.0 STD LP2985IBP-3.0 250 Units on Tape and Reel 3.0 STD LP2985IBPX-3.0 3000 Units on Tape and Reel 3.3 A LP2985AIBP-3.3 250 Units on Tape and Reel www.national.com 4 LP2985 Ordering Information (Continued) TABLE 1. Package Marking and Ordering Information (Continued) Output Voltage (V) Grade Package Marking Order Information Supplied as: micro SMD, 5 Bump Package (BPA05) 3.3 A LP2985AIBPX-3.3 3000 Units on Tape and Reel 3.3 STD LP2985IBPX-3.3 250 Units on Tape and Reel 3.3 STD LP2985IBPX-3.3 3000 Units on Tape and Reel 3.6 A LP2985AIBP-3.6 250 Units on Tape and Reel 3.6 A LP2985AIBPX-3.6 3000 Units on Tape and Reel 3.6 STD LP2985IBP-3.6 250 Units on Tape and Reel 3.6 STD LP2985IBPX-3.6 3000 Units on Tape and Reel 4.0 A LP2985AIBP-4.0 250 Units on Tape and Reel 4.0 A LP2985AIBPX-4.0 3000 Units on Tape and Reel 4.0 STD LP2985IBP-4.0 250 Units on Tape and Reel 4.0 STD LP2985IBPX-4.0 3000 Units on Tape and Reel 5.0 A LP2985AIBP-5.0 250 Units on Tape and Reel 5.0 A LP2985AIBPX-5.0 3000 Units on Tape and Reel 5.0 STD LP2985IBP-5.0 250 Units on Tape and Reel 5.0 STD LP2985IBPX-5.0 3000 Units on Tape and Reel 5 www.national.com LP2985 Absolute Maximum Ratings (Note 1) Input Supply Voltage (Survival) Input Supply Voltage (Operating) Shutdown Input Voltage (Survival) Output Voltage (Survival, (Note 4)) IOUT (Survival) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Storage Temperature Range Operating Junction Temperature Range Lead Temp. (Soldering, 5 sec.) ESD Rating (Note 2) Power Dissipation (Note 3) −65˚C to +150˚C −40˚C to +125˚C 260˚C 2 kV Internally Limited −0.3V to +16V 2.5V to +16V −0.3V to +16V −0.3V to +9V Short Circuit Protected −0.3V to +16V Input-Output Voltage (Survival, (Note 5)) Electrical Characteristics Limits in standard typeface are for TJ = 25˚C. and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VO(NOM) + 1V, IL = 1 mA, CIN = 1 µF, COUT = 4.7 µF, VON/OFF = 2V. LP2985AI-X.X Symbol ∆VO Parameter Output Voltage Tolerance Conditions Typ Dropout Voltage (Note 7) Max IL = 1 mA −1.0 1.0 −1.5 1.5 1 mA ≤ IL ≤ 50 mA −1.5 1.5 −2.5 2.5 −2.5 2.5 −3.5 3.5 VO(NOM)+1V ≤ VIN ≤ 16V IL = 0 −2.5 2.5 −3.0 3.0 −3.5 3.5 −4.0 4.0 0.007 1 7 IL = 10 mA 40 IL = 50 mA Ground Pin Current 120 IL = 150 mA 280 IL = 0 65 IL = 1 mA 75 IL = 10 mA VON/OFF ION/OFF ON/OFF Input Voltage (Note 8) ON/OFF Input Current 120 0.014 0.032 0.032 3 3 5 5 10 10 15 15 60 60 90 90 150 150 225 225 350 350 575 575 95 95 125 125 110 110 170 170 220 220 400 400 600 350 600 1000 1000 IL = 150 mA 850 1500 1500 2500 2500 VON/OFF < 0.3V 0.01 0.8 0.8 VON/OFF < 0.15V 0.05 2 High = O/P ON 1.4 Low = O/P OFF 0.55 0.15 0.15 VON/OFF = 0 0.01 −2 −2 5 15 15 Output Noise BW = 300 Hz to 50 kHz, Voltage (RMS) COUT = 10 µF 30 CBYPASS = 10 nF www.national.com 0.014 IL = 50 mA VON/OFF = 5V en Units Min IL = 1 mA IGND (Note 6) Max Line Regulation VIN–VO LP2985I-X.X Min 1 mA ≤ IL ≤ 150 mA Output Voltage (Note 6) 6 1.6 %VNOM %/V mV µA 2 1.6 V µA µV (Continued) Limits in standard typeface are for TJ = 25˚C. and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VO(NOM) + 1V, IL = 1 mA, CIN = 1 µF, COUT = 4.7 µF, VON/OFF = 2V. LP2985AI-X.X Symbol Parameter Conditions Typ (Note 6) Min Ripple Rejection Short Circuit Current RL = 0 (Steady State) (Note 9) IO(PK) Peak Output Current (Note 6) Min Units Max f = 1 kHz, CBYPASS = 10 nF COUT = 10 µF IO(SC) Max LP2985I-X.X VOUT ≥ Vo(NOM) −5% 45 dB 400 mA 350 mA Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its rated operating conditions. Note 2: The ESD rating of pins 3 and 4 is 1 kV. Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, θJ-A, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperture is calculated using: Where the value of θJ-A for the SOT-23 package is 220˚C/W in a typical PC board mounting and the micro SMD package is 320˚C/W. Exceeding the maximum allowable dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Note 4: If used in a dual-supply system where the regulator load is returned to a negative supply, the LP2985 output must be diode-clamped to ground. Note 5: The output PNP structure contains a diode between the VIN to VOUT terminals that is normally reverse-biased. Reversing the polarity from VIN to VOUT will turn on this diode. Note 6: Limits are 100% production tested at 25˚C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. The limits are used to calculate National’s Average Outgoing Quality Level (AOQL). Note 7: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential. Note 8: The ON/OFF input must be properly driven to prevent possible misoperation. For details, refer to Application Hints. Note 9: The LP2985 has foldback current limiting which allows a high peak current when VOUT forced to ground (see Typical Performance Characteristics curves). 7 > 0.5V, and then reduces the maximum output current as VOUT is www.national.com LP2985 Electrical Characteristics LP2985 Typical Performance Characteristics Unless otherwise specified: CIN = 1µF, COUT = 4.7µF, VIN = VOUT(NOM) +1, TA = 25˚C, ON/OFF pin is tied to VIN. VOUT vs Temperature Short-Circuit Current DS100140-9 DS100140-8 Short-Circuit Current Short Circuit Current vs Output Voltage DS100140-10 DS100140-11 Ripple Rejection Ripple Rejection DS100140-13 www.national.com DS100140-14 8 Unless otherwise specified: CIN = 1µF, COUT = 4.7µF, VIN = VOUT(NOM) +1, TA = 25˚C, ON/OFF pin is tied to VIN. (Continued) Ripple Rejection Ripple Rejection DS100140-15 Ripple Rejection DS100140-16 Ripple Rejection DS100140-17 Ripple Rejection DS100140-18 Ripple Rejection DS100140-19 DS100140-23 9 www.national.com LP2985 Typical Performance Characteristics LP2985 Typical Performance Characteristics Unless otherwise specified: CIN = 1µF, COUT = 4.7µF, VIN = VOUT(NOM) +1, TA = 25˚C, ON/OFF pin is tied to VIN. (Continued) Ripple Rejection Output Impedance vs Frequency DS100140-20 DS100140-22 Output Impedance vs Frequency Output Noise Density DS100140-24 DS100140-21 Output Noise Density Ground Pin vs Load Current DS100140-25 www.national.com DS100140-26 10 Unless otherwise specified: CIN = 1µF, COUT = 4.7µF, VIN = VOUT(NOM) +1, TA = 25˚C, ON/OFF pin is tied to VIN. (Continued) Dropout Voltage vs Temperature Dropout Voltage vs Load Current DS100140-27 Input Current vs Pin DS100140-28 GND Pin Current vs Temperature DS100140-30 DS100140-29 Instantaneous Short Circuit Current Load Transient Response DS100140-32 DS100140-31 11 www.national.com LP2985 Typical Performance Characteristics LP2985 Typical Performance Characteristics Unless otherwise specified: CIN = 1µF, COUT = 4.7µF, VIN = VOUT(NOM) +1, TA = 25˚C, ON/OFF pin is tied to VIN. (Continued) Load Transient Response Load Transient Response DS100140-33 Line Transient Response DS100140-34 Line Transient Response DS100140-35 Line Transient Response DS100140-36 Line Transient Response DS100140-37 www.national.com DS100140-38 12 Unless otherwise specified: CIN = 1µF, COUT = 4.7µF, VIN = VOUT(NOM) +1, TA = 25˚C, ON/OFF pin is tied to VIN. (Continued) Turn-On Time Turn-On Time DS100140-39 Turn-On Time DS100140-40 Turn-On Time DS100140-41 DS100140-42 tor to be stable across the entire range of output current with an output capacitor whose ESR is as low as 5 mΩ. It may also be possible to use Tantalum or film capacitors at the output, but these are not as attractive for reasons of size and cost (see next section Capacitor Characteristics). The output capacitor must meet the requirement for minimum amount of capacitance and also have an ESR (equivalent series resistance) value which is within the stable range. Curves are provided which show the stable ESR range as a function of load current (see ESR graph below). Application Hints EXTERNAL CAPACITORS Like any low-dropout regulator, the LP2985 requires external capacitors for regulator stability. These capacitors must be correctly selected for good performance. Input Capacitor An input capacitor whose capacitance is ≥ 1 µF is required between the LP2985 input and ground (the amount of capacitance may be increased without limit). This capacitor must be located a distance of not more than 1 cm from the input pin and returned to a clean analog ground. Any good quality ceramic, tantalum, or film capacitor may be used at the input. Important: Tantalum capacitors can suffer catastrophic failure due to surge current when connected to a low-impedance source of power (like a battery or very large capacitor). If a Tantalum capacitor is used at the input, it must be guaranteed by the manufacturer to have a surge current rating sufficient for the application. There are no requirements for ESR on the input capacitor, but tolerance and temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will be ≥ 1 µF over the entire operating temperature range. Output Capacitor: The LP2985 is designed specifically to work with ceramic output capacitors, utilizing circuitry which allows the regula- DS100140-7 13 www.national.com LP2985 Typical Performance Characteristics LP2985 Application Hints Another important consideration is that Tantalum capacitors have higher ESR values than equivalent size ceramics. This means that while it may be possible to find a Tantalum capacitor with an ESR value within the stable range, it would have to be larger in capacitance (which means bigger and more costly) than a ceramic capacitor with the same ESR value. (Continued) Important: The output capacitor must maintain its ESR within the stable region over the full operating temperature range of the application to assure stability. The LP2985 requires a minimum of 2.2 µF on the output (output capacitor size can be increased without limit). It should also be noted that the ESR of a typical Tantalum will increase about 2:1 as the temperature goes from 25˚C down to −40˚C, so some guard band must be allowed. It is important to remember that capacitor tolerance and variation with temperature must be taken into consideration when selecting an output capacitor so that the minimum required amount of output capacitance is provided over the full operating temperature range. It should be noted that ceramic capacitors can exhibit large changes in capacitance with temperature (see next section, Capacitor Characteristics). The output capacitor must be located not more than 1 cm from the output pin and returned to a clean analog ground. Noise Bypass Capacitor: Connecting a 10 nF capacitor to the Bypass pin significantly reduces noise on the regulator output. It should be noted that the capacitor is connected directly to a high-impedance circuit in the bandgap reference. Because this circuit has only a few microamperes flowing in it, any significant loading on this node will cause a change in the regulated output voltage. For this reason, DC leakage current through the noise bypass capacitor must never exceed 100 nA, and should be kept as low as possible for best output voltage accuracy. The types of capacitors best suited for the noise bypass capacitor are ceramic and film. High-quality ceramic capacitors with either NPO or COG dielectric typically have very low leakage. 10 nF polypropolene and polycarbonate film capacitors are available in small surface-mount packages and typically have extremely low leakage current. ON/OFF INPUT OPERATION The LP2985 is shut off by driving the ON/OFF input low, and turned on by pulling it high. If this feature is not to be used, the ON/OFF input should be tied to VIN to keep the regulator output on at all times. To assure proper operation, the signal source used to drive the ON/OFF input must be able to swing above and below the specified turn-on/turn-off voltage thresholds listed in the Electrical Characteristics section under VON/OFF. To prevent mis-operation, the turn-on (and turn-off) voltage signals applied to the ON/OFF input must have a slew rate which is ≥ 40 mV/µs. Caution: the regulator output voltage can not be guaranteed if a slow-moving AC (or DC) signal is applied that is in the range between the specified turn-on and turn-off voltages listed under the electrical specification VON/OFF (see Electrical Characteristics). REVERSE INPUT-OUTPUT VOLTAGE The PNP power transistor used as the pass element in the LP2985 has an inherent diode connected between the regulator output and input. During normal operation (where the input voltage is higher than the output) this diode is reverse-biased. However, if the output is pulled above the input, this diode will turn ON and current will flow into the regulator output. In such cases, a parasitic SCR can latch which will allow a high current to flow into VIN (and out the ground pin), which can damage the part. In any application where the output may be pulled above the input, an external Schottky diode must be connected from VIN to VOUT (cathode on VIN, anode on VOUT), to limit the reverse voltage across the LP2985 to 0.3V (see Absolute Maximum Ratings). CAPACITOR CHARACTERISTICS The LP2985 was designed to work with ceramic capacitors on the output to take advantage of the benefits they offer: for capacitance values in the 2.2 µF to 4.7 µF range, ceramics are the least expensive and also have the lowest ESR values (which makes them best for eliminating high-frequency noise). The ESR of a typical 2.2 µF ceramic capacitor is in the range of 10 mΩ to 20 mΩ, which easily meets the ESR limits required for stability by the LP2985. One disadvantage of ceramic capacitors is that their capacitance can vary with temperature. Most large value ceramic capacitors (≥ 2.2 µF) are manufactured with the Z5U or Y5V temperature characteristic, which results in the capacitance dropping by more than 50% as the temperature goes from 25˚C to 85˚C. This could cause problems if a 2.2 µF capacitor were used on the output since it will drop down to approximately 1 µF at high ambient temperatures (which could cause the LM2985 to oscillate). If Z5U or Y5V capacitors are used on the output, a minimum capacitance value of 4.7 µF must be observed. A better choice for temperature coefficient in ceramic capacitors is X7R, which holds the capacitance within ± 15%. Unfortunately, the larger values of capacitance are not offered by all manufacturers in the X7R dielectric. Tantalum: Tantalum capacitors are less desirable than ceramics for use as output capacitors because they are more expensive when comparing equivalent capacitance and voltage ratings in the 1 µF to 4.7 µF range. www.national.com Micro SMD Mounting The micro SMD package requires specific mounting techniques which are detailed in National Semiconductor Application Note # 1112. Referring to the section Surface Mount Technology (SMT) Assembly Considerations, it should be noted that the pad style which must be used with the 5-pin package is the NSMD (non-solder mask defined) type. For best results during assembly, alignment ordinals on the PC board may be used to facilitate placement of the micro SMD device. Micro SMD Light Sensitivity Exposing the micro SMD device to direct sunlight will cause misoperation of the device. Light sources such as Halogen lamps can also affect electrical performance if brought near to the device. The wavelenghts which have the most detrimental effect are reds and infra-reds, which means that the fluorescent lighting used inside most buildings has very little effect on perfor14 output voltage was negligible, showing a deviation of less than 0.1% from nominal. (Continued) mance. A micro SMD test board was brought to within 1 cm of a fluorescent desk lamp and the effect on the regulated 15 www.national.com LP2985 Application Hints LP2985 Physical Dimensions inches (millimeters) unless otherwise noted 5-Lead Small Outline Package (M5) NS Package Number MF05A For Order Numbers, refer to Table 1 in the “Ordering Information” section of this document. www.national.com 16 LP2985 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) NOTES: UNLESS OTHERWISE SPECIFIED 1. EPOXY COATING 2. 63Sn/37Pb EUTECTIC BUMP 3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD. 4. PIN 1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION. REMAINING PINS ARE NUMBERED COUNTER CLOCKWISE. 5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACKAGE HEIGHT. 6.NO JEDEC REGISTRATION AS OF AUG.1999. micro SMD, 5 Bump, Package (BPA05) NS Package Number BPA05A For Order Numbers, refer to Table 1 in the “Ordering Information” section of this document. The dimensions for X1, X2 and X3 are as given: X1 = 0.930 +/− 0.030mm X2 = 1.107 +/− 0.030mm X3 = 0.850 +/− 0.050mm 17 www.national.com LP2985 Micropower 150 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and micro SMD Packages Notes LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL 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 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 to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 2. A critical component is 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. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.