LP3991 300mA Linear Voltage Regulator for Digital Applications General Description Features Operating from a minimum input voltage of 1.65V, the LP3991 regulator has been designed to provide fixed stable output voltages for load currents up to 300mA. This device is suitable where accurate, low voltages are required from low input voltage sources and is therefore suitable for post regulation of switched mode regulators. In such applications, significant improvements in performance and EMI can be realized, with little reduction in overall efficiency. The LP3991 will provide fixed outputs as low as 1.2V from a wide input range of 1.65V to 4.0V Using the enable pin, the device may be controlled to provide a shutdown state, in which negligible supply current is drawn. The LP3991 is designed to be stable with space saving ceramic capacitors as small as 0402 case size. Performance is specified for a -40°C to 125°C junction temperature range. For output voltage options please contact your local NSC sales office. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Operation from 1.65V to 4.0V Input 1% accuracy at room temperature Output Voltage from 1.2V to 2.8V 125mV Dropout at 300mA load 50µA Quiescent Current at 1mA Load Inrush Current controlled to 600mA PSRR 65dB at 1kHz 100µs Start-Up time for 1.5V VOUT Stable with Ceramic Capacitors as small as 0402 Thermal-Overload and Short-Circuit Protection Package 4 pin micro SMD (0.963mm x 1.446mm) For other package options contact your NSC sales office. Applications ■ Post DC/DC Regulator ■ Battery Operated Devices ■ Hand-Held Information Appliances Typical Application Circuit 20110002 © 2007 National Semiconductor Corporation 201100 www.national.com LP3991 300mA Linear Voltage Regulator for Digital Applications December 13, 2007 LP3991 Pin Descriptions Packages Pin No. Symbol Name and Function B1 VOUT Voltage output. A Low ESR Ceramic Capacitor should be connected from this pin to GND. (See Application Information) Connect this output to the load circuit. A1 GND Common Ground. Connect to Pad. A2 VEN Enable Input; Enables the Regulator when ≥ 0.95V. Disables the Regulator when ≤ 0.4V. Enable Input has an internal 1.2MΩ pull-down resistor to GND. B2 VIN Voltage Supply Input. A 1.0µF capacitor should be connected from this pin to GND. Connection Diagram 4 Bump Thin Micro SMD, Large Bump 20110006 See NS package number TLA04 Ordering Information (4-Bump Micro SMD) Only available as Lead Free. Output Voltage (V) Grade LP3991 Supplied as 1000 Units, Tape and Reel LP3991 Supplied as 3000 Units, Tape and Reel 0.8 STD LP3991TL-0.8 LP3991TLX-0.8 1.2 STD LP3991TL-1.2 LP3991TLX-1.2 1.3 STD LP3991TL-1.3 LP3991TLX-1.3 1.5 STD LP3991TL-1.5 LP3991TLX-1.5 1.8 STD LP3991TL-1.8 LP3991TLX-1.8 2.0 STD LP3991TL-2.0 LP3991TLX-2.0 2.5 STD LP3991TL-2.5 LP3991TLX-2.5 2.8 STD LP3991TL-2.8 LP3991TLX-2.8 3.0 STD LP3991TL-3.0 LP3991TLX-3.0 www.national.com 2 LP3991 Absolute Maximum Ratings (Notes 1, 2) Operating Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. (Note 1) Input Voltage Range Recommended Load Current Junction Temperature Ambient Temperature TARange (Note 6) VIN, VOUT, Pins: Voltage to GND -0.3 to 6.5V VEN Pin: Voltage to GND -0.3 to (VIN + 0.3V) to 6.5V (max) Junction Temperature 150°C Lead/Pad Temp. (Note 3) Micro SMD 260°C Storage Temperature -65 to 150°C Continuous Power Dissipation Internally Limited (Note 4) ESD (Note 5) Human Body Model 2KV Machine Model 200V Thermal Properties 1.65 to 4.0V 300mA -40°C to 125°C -40°C to 85°C (Note 1) Junction To Ambient Thermal Resistance(Note 7) θJA JEDEC Board (Note 8) 88°C/W θJA 4 Layer Board 160°C/W Electrical Characteristics Unless otherwise noted, VEN =950mV, VIN = VOUT + 0.5V, or 1.8V, whichever is higher. CIN = 1µF, IOUT = 1.0mA, COUT =4.7µF. Typical values and limits appearing in normal type apply for TA = 25°C. Limits appearing in boldface type apply over the full junction temperature range for operation, −40 to +125°C. (Note 9) Symbol VIN ΔVOUT Parameter Input Voltage Conditions Typ (Note 10) Limit Min Max 1.65 3.6 (Note 16) Output Voltage Tolerance 4.0 VIN = VIN(NOM) to 3.6V ILOAD = 1 to 300mA VIN = VOUT(NOM) +0.5V to 3.6V, IOUT = 1mA V -1.0 -3.0 1.0 3.0 -2.5 2.5 % 0.05 1 %/V 10 60 µV/mA Temperature (TJ)= -25°C to +85°C Line Regulation Error Units 0.8V ≤ VOUT ≤ 2.8V VDO Load Regulation Error IOUT = 1mA to 300mA Dropout Voltage(Note 11) 1.8 ≤ VOUT ≤ 2.5V VOUT > 2.5V IOUT = 150mA 55 90 IOUT = 300mA 110 180 IOUT = 150mA 40 80 IOUT = 300mA 75 160 ILOAD Minimum Load Current (Note 12) IQ Quiescent Current VEN = 950mV, IOUT = 0mA 0 VEN = 950mV, IOUT = 300mA VEN = 0.4V ISC Short Circuit Current Limit IOUT Maximum Output Current PSRR Power Supply Rejection Ratio (Note 14) en TSHUTDOWN VIN = 3.6V (Note 13) 100 120 225 0.001 1.0 900 300 f = 1kHz, IOUT = 1mA to 300mA 65 Output noise Voltage (Note 14) BW = 10Hz to 100kHz, VIN = 4.2V, COUT = 4.7µF 280 Thermal Shutdown Temperature 160 Hysteresis 20 3 mA 50 550 mV µA mA mA dB µVRMS °C www.national.com LP3991 Electrical Characteristics con't. Unless otherwise noted, VEN =950mV, VIN = VOUT + 0.5V, or 1.8V, whichever is higher. CIN = 1µF, IOUT = 1.0mA, COUT =4.7µF. Typical values and limits appearing in normal type apply for TA = 25°C. Limits appearing in boldface type apply over the full junction temperature range for operation, −40 to +125°C. (Note 9) Symbol Parameter Conditions Typ Limit Min Max Units Enable Control Characteristics IEN (Note 15) Maximum Input Current at VEN Input VEN = 0V, VIN = 3.6V VIL Low Input Threshold VIN = 1.65V to 3.6V VIH High Input Threshold VIN = 1.65V to 3.6V VEN = VIN = 3.6V 0.001 3 µA 5.5 V 0.4 V 0.95 Timing Characteristics TON Turn On Time (Note 14) To 95% Level VIN(MIN) to 3.6V VOUT ≤ 2.0V 100 VOUT > 2.0V 140 Line Transient Response |δVOUT| Trise = Tfall = 30µs (Note 14) δVIN = 600mV Transient Response IIR 140 IOUT = 300mA to 1mA 80 IOUT = 0mA to 200mA 110 IOUT = 1mA to 200mA 80 110 IOUT = 200mA to 1mA 60 IOUT = 0mA to 150mA 100 IOUT = 1mA to 150mA 70 IOUT = 150mA to 1mA 50 In-Rush Current (Note 14) mV (pk - pk) 6 Load Transient Response |δVOUT| Trise = Tfall = 1µs IOUT = 0 mA to 300mA (Note 14) IOUT = 1mA to 300mA Overshoot on Start-up µs mV 0 2 % 600 1000 mA Note 1: Absolute Maximum Ratings are limits beyond which damage can occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 2: All Voltages are with respect to the potential at the GND pin. Note 3: For further information on these packages please refer to the following application notes,AN-1112 Micro SMD Wafer Level Chip Scale Package. Note 4: Internal thermal shutdown circuitry protects the device from permanent damage. Note 5: The human body model is 100pF discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged directly into each pin. Note 6: The maximum ambient temperature (TA(max)) is dependant on the maximum operating junction temperature (TJ(max-op) = 125°C), the maximum power dissipation of the device in the application (PD(max)), and the junction to ambient thermal resistance of the part / package in the application (θJA), as given by the following equation: TA(max) = TJ(max-op) - (θJA × PD(max)). Note 7: Junction to ambient thermal resistance is dependant on the application and board layout. In applications where high maximum power dissipation is possible, special care must be paid to thermal dissipation issues in board design. Note 8: Full details can be found in JESD61-7 Note 9: All limits are guaranteed. All electrical characteristics having room-temperature limits are tested during production at TJ = 25°C or correlated using Statistical Quality Control methods. Operation over the temperature specification is guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control. Note 10: VIN(MIN) = VOUT(NOM) + 0.5V or 1.65V, whichever is greater. (See post DC/DC convertor example in application information section). Note 11: Dropout voltage is voltage difference between input and output at which the output voltage drops to 100mV below its nominal value. This parameter is only specified for output voltages above 1.8V. Note 12: The device maintains the regulated output voltage without a load. Note 13: Short circuit current is measured with VOUT pulled to 0V. Note 14: This electrical specification is guaranteed by design. Note 15: Enable Pin has an internal 1.2MΩ typical, resistor connected to GND. Note 16: The device will operate with input voltages up to 4.0V. However special care should be taken in relation to thermal dissipation and the need to derate the maximum allowable ambient temperature. See (Notes 6, 7) www.national.com 4 LP3991 Output Capacitor, Recommended Specifications Parameter COUT Output Capacitor Conditions Capacitance (Note 17) ESR Typ Limit Min VOUT ≥ 1.5V 4.7 2 VOUT < 1.5V (Note 18) 2.2 1.6 5 Max Units µF 500 mΩ Note 17: The capacitor tolerance should be 30% or better over temperature. The full operating conditions for the application should be considered when selecting a suitable capacitor to ensure that the minimum value of capacitance is always met. Recommended capacitor type is X7R or X5R. (See capacitor section in Applications Hints) Note 18: On lower voltage options, 2.2µF output capacitor may be used but some degradation in load transient (10 -15%) can be expected, compared to a 4.7µF. 5 www.national.com LP3991 Typical Performance Characteristics. Unless otherwise specified, CIN = 1.0µF Ceramic, COUT = 4.7µF Ceramic, VIN = VOUT(NOM) + 0.5V or 1.8V whichever is greater, TA = 25°C, VOUT(NOM) = 1.5V , Shutdown pin is tied to VIN. Output Voltage Change vs Temperature Output Voltage vs Minimum Input Voltage 20110010 20110009 Ground Current vs Load Current Ground Current vs VIN. ILOAD = 1mA 20110011 20110012 Dropout Voltage Dropout Voltage vs Output Voltage 20110015 20110014 www.national.com 6 Unless otherwise specified, CIN = 1.0µF Ceramic, COUT = 4.7µF Ceramic, VIN = VOUT(NOM) + 0.5V or 1.8V whichever is greater, TA = 25°C, VOUT(NOM) = 1.5V , Shutdown pin is tied to VIN. Load Transient, VOUT = 1.5V Load Transient, VOUT = 1.2V 20110018 20110021 Line Transient, ILOAD = 1mA Line Transient, ILOAD = 300mA 20110019 20110020 Enable Characteristics Short Circuit Current 20110022 20110023 7 www.national.com LP3991 Typical Performance Characteristics con't. LP3991 Typical Performance Characteristics con't. Unless otherwise specified, CIN = 1.0µF Ceramic, COUT = 4.7µF Ceramic, VIN = VOUT(NOM) + 0.5V or 1.8V whichever is greater, TA = 25°C, VOUT(NOM) = 1.5V , Shutdown pin is tied to VIN. Power Supply Rejection Ratio Power Supply Rejection Ratio 20110025 20110026 Noise Density 20110028 www.national.com 8 EXTERNAL CAPACITORS In common with most regulators, the LP3991 requires external capacitors for regulator stability. The LP3991 is specifically designed for portable applications requiring minimum board space and smallest components. These capacitors must be correctly selected for good performance. INPUT CAPACITOR An input capacitor is required for stability. It is recommended that a 1.0µF capacitor be connected between the LP3991 input pin and ground (this capacitance value may be increased without limit). This capacitor must be located a distance of not more than 1cm from the input pin and returned to a clean analogue ground. Any good quality ceramic, tantalum, or film capacitor may be used at the input. Important: Tantalum capacitors can suffer catastrophic failures due to surge current when connected to a lowimpedance source of power (like a battery or a 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 the ESR (Equivalent Series Resistance) on the input capacitor, but tolerance, temperature, and voltage coefficients must be considered when selecting the capacitor to ensure the capacitance will remain ≊ 1.0µF over the entire operating temperature range. OUTPUT CAPACITOR Correct selection of the output capacitor is critical to ensure stable operation in the intended application. The output capacitor must meet all the requirements specified in the recommended capacitor table over all conditions in the application. these conditions include DC bias, frequency and temperature. Unstable operation will result if the capacitance drops below the minimum specified value. The LP3991 is designed specifically to work with very small ceramic output capacitors. For voltage options of 1.5V and higher, A 4.7µF ceramic capacitor (dielectric type X7R or X5R) with an ESR between 5mΩ to 500mΩ, is suitable in the LP3991 application circuit. However, on lower VOUT options a 2.2µF may be employed with only a small increase in load transient. Other ceramic types such as Y5V and Z5U are less suitable owing to their inferior temperature characteristics. (See section on Capacitor Characteristics). It is also recommended that the output capacitor is placed within 1cm of the output pin and returned to a clean, low impedance, ground connection. It is possible to use tantalum or film capacitors at the device output, VOUT, but these are not as attractive for reasons of size and cost (see the section Capacitor Characteristics). 20110040 FIGURE 1. Effect of DC bias on Capacitance Value. As an example Figure 1 shows a typical graph showing a comparison of capacitor case sizes in a Capacitance vs. DC Bias plot. As shown in the graph, as a result of the DC Bias condition, the capacitance value may drop below the minimum capacitance value given in the recommended capacitor table. Note that the graph shows the capacitance out of spec for the 0402 case size capacitor at higher bias voltages. It is therefore recommended that the capacitor manufacturers' specifications for the nominal value capacitor are consulted for all conditions as some capacitor sizes (e.g. 0402) may not be suitable in the actual application. Ceramic capacitors have the lowest ESR values, thus making them best for eliminating high frequency noise. The ESR of a typical 4.7µF ceramic capacitor is in the range of 20mΩ to 40mΩ, which easily meets the ESR requirement for stability for the LP3991. The temperature performance of ceramic capacitors varies by type. Capacitor type X7R is specified with a tolerance of ±15% over the temperature range -55°C to +125°C. The X5R has a similar tolerance over the reduced temperature range of -55° C to +85°C. Some large value ceramic capacitors (4.7µF) are manufactured with Z5U or Y5V temperature characteristics, which can result in the capacitance dropping by more than 50% as the temperature varies from 25°C to 85°C. Therefore X7R or X5R types are recommended in applications where the temperature will change significantly above or below 25° C. Tantalum capacitors are less desirable than ceramic for use as output capacitors because they are more expensive when comparing equivalent capacitance and voltage ratings in the NO-LOAD STABILITY The LP3991 will remain stable and in regulation with no external load. This is an important consideration in some circuits, for example CMOS RAM keep-alive applications. CAPACITOR CHARACTERISTICS The LP3991 is designed to work with ceramic capacitors on the input and output to take advantage of the benefits they offer. For capacitance values around 4.7µF, ceramic capaci- 9 www.national.com LP3991 tors give the circuit designer the best design options in terms of low cost and minimal area. For both input and output capacitors, careful interpretation of the capacitor specification is required to ensure correct device operation. The capacitor value can change greatly dependant on the conditions of operation and capacitor type. In particular, to ensure stability, the output capacitor selection should take account of all the capacitor parameters, to ensure that the specification is met within the application. Capacitance value can vary with DC bias conditions as well as temperature and frequency of operation. Capacitor values will also show some decrease over time due to aging. The capacitor parameters are also dependant on the particular case size with smaller sizes giving poorer performance figures in general. Application Information LP3991 1µF to 4.7µF range. 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. 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. micro SMD MOUNTING The micro SMD package requires specific mounting techniques which are detailed in the National Semiconductor Application Note (AN-1112). Referring to the section Surface Mount Technology (SMT) Assenbly Considerations, it should be noted that the pad style which must be used with the 4 pin package is NSMD (non-solder mask defined) type. For best results during assembly, alignment ordinals on the PCB may be used to facilitate placement of the micro SMD device. ENABLE CONTROL The LP3991 features an active high Enable pin, VEN, which turns the device on when pulled high. When not enabled the regulator output is off and the device typically consumes 2nA. If the application does not require the Enable switching feature, the VEN pin should be tied to VIN to keep the regulator output permanently on. To ensure proper operation, the signal source used to drive the VEN input must be able to swing above and below the specified turn-on/off voltage thresholds listed in the Electrical Characteristics section under VIL and VIH. micro SMD LIGHT SENSITIVITY Exposing the micro SMD device to direct sunlight may cause mis-operation of the device. Light sources such as halogen lamps can affect the electrical performance if brought near to the device. The wavelengths which have most detrimental effect are reds and infra-reds, which means that fluorescent lighting, used inside most buildings will have little effect on performance. 20110036 FIGURE 2. LP3991 Used as a Post DC/DC regulator POST-BUCK REGULATOR Linear Post-Regulation can be an effective way to reduce ripple and switching noise from DC/DC convertors while still maintaining a reasonably high overall efficiency. The LP3991 is particularly suitable for this role due to its low input voltage requirements. In addition, there is often no need for a separate input capacitor for the LP3991 as it can share the output cap of the DC/DC convertor. Care of PCB layouts involving switching regulators is paramount. In particular, the ground paths for the LDO should be routed separately from the switcher ground and star connected close to the battery. Routing of the switch pin of the DC/DC convertor must be kept short to minimize radiated EMI. A low pass filter such as a ferrite bead or common mode choke on the battery input leads can further reduce radiated EMI. Figure 2 shows a typical example using an LM3673, 350mA DC/DC buck regulator with a nominal output of 1.8V and a 1.5V LP3991. The overall efficiency will be greater than 70% over the full Li-Ion battery voltage range. Maximum efficiency is achieved by minimizing the difference between VIN and VOUT of the LP3991. The LP3991-1.5 will remain in regulation down to an input voltage of 1.65V, so, in this case, a 1.8V buck with 5% tolerance is adequate for all conditions of temperature and load. www.national.com MAXIMUM SUPPLY VOLTAGE AND THERMAL CONSIDERATIONS Maximum recommended input voltage is 3.6V. The device may be operated at 4.0V VIN if proper care is given to the board design in regard to thermal dissipation. As a guide please refer to the following table for ambient temperature at 2 input voltages and 2 load currents for the example board types. θJA VIN VOUT IOUT PD Ambient Temp. 88ºC/W 3.6V 2.8V 160mA 0.130W 113ºC 250mA 0.200W 107ºC 4.0V 2.8V 160mA 0.190W 108ºC 250mA 0.300W 98ºC 160mA 0.130W 104ºC 250mA 0.200W 93ºC 160mA 0.190W 94ºC 250mA 0.300W 77ºC 160ºC/W 3.6V 4.0V 10 2.8V 2.8V LP3991 Physical Dimensions inches (millimeters) unless otherwise noted 4 Bump Thin micro SMD, Large Bump NS Package Number TLA04ZTA The Dimensions for X1, X2 and X3 as given as: X1 = 0.963mm ± 0.030mm X2 = 1.446mm ± 0.03mm X3 = 0.60mm ± 0.075mm 11 www.national.com LP3991 300mA Linear Voltage Regulator for Digital Applications Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench Audio www.national.com/audio Analog University www.national.com/AU Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes Data Converters www.national.com/adc Distributors www.national.com/contacts Displays www.national.com/displays Green Compliance www.national.com/quality/green Ethernet www.national.com/ethernet Packaging www.national.com/packaging Interface www.national.com/interface Quality and Reliability www.national.com/quality LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns Power Management www.national.com/power Feedback www.national.com/feedback Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www.national.com/led PowerWise www.national.com/powerwise Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors Wireless (PLL/VCO) www.national.com/wireless THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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