LP2953QML Adjustable Micropower Low-Dropout Voltage Regulators General Description Features The LP2953A is a micropower voltage regulator with very low quiescent current (130 A typical at 1 mA load) and very low dropout voltage (typ. 60 mV at light load and 470 mV at 250 mA load current). It is ideally suited for battery-powered systems. Furthermore, the quiescent current increases only slightly at dropout, which prolongs battery life. The LP2953A retains all the desirable characteristics of the LP2951, but offers increased output current, additional features, and an improved shutdown function. The internal crowbar pulls the output down quickly when the shutdown is activated. The error flag goes low if the output voltage drops out of regulation. Reverse battery protection is provided. The internal voltage reference is made available for external use, providing a low-T.C. reference with very good line and load regulation. Output voltage adjusts from 1.23V to 29V Guaranteed 250 mA output current Extremely low quiescent current Low dropout voltage Extremely tight line and load regulation Very low temperature coefficient Current and thermal limiting Reverse battery protection 50 mA (typical) output pulldown crowbar Auxiliary comparator included with CMOS/TTL compatible output levels. Can be used for fault detection, low input line detection, etc. Applications High-efficiency linear regulator Regulator with under-voltage shutdown Low dropout battery-powered regulator Snap-ON/Snap-OFF regulator Ordering Information NS Part Number SMD Part Number NS Package Number LP2953AMWG/883 5962-9233601QXA WG16A 16LD Ceramic SOIC LP2953AMWG-QMLV 5962-9233601VXA WG16A 16LD Ceramic SOIC LP2953AMGW/883 5962-9233602QXA WG16A 16LD Ceramic SOIC LP2953AMGW-QMLV 5962-9233602VXA WG16A 16LD Ceramic SOIC (Note 1) Bare Die LP2953 MDS Package Description Note 1: FOR ADDITIONAL DIE INFORMATION, PLEASE VISIT THE HI REL WEB SITE AT: www.national.com/analog/space/level_die Connection Diagrams LP2953 16-Pin Ceramic SOIC 20161114 (c) 2011 National Semiconductor Corporation 201611 www.national.com LP2953QML Adjustable Micropower Low-Dropout Voltage Regulators September 1, 2011 LP2953QML Schematic Diagram 20161106 www.national.com 2 LP2953QML Block Diagram LP2953 20161102 3 www.national.com LP2953QML Absolute Maximum Ratings (Note 2) -65C TA +150C Storage Temperature Range -55C TA +125C +150C 260C Internally Limited -20V to +30V -0.3V to +5V -0.3V to +30V -0.3V to +30V -0.3V to +30V Operating Temperature Range Maximum Junction Temperature Lead Temp. (Soldering, 5 seconds) Power Dissipation (Note 3) Input Supply Voltage Feedback Input Voltage (Note 5) Comparator Input Voltage (Note 6) Shutdown Input Voltage (Note 6) Comparator Output Voltage (Note 6) Thermal Resistance JA 16LD Ceramic SOIC (Still Air) "WG" 16LD Ceramic SOIC (500LF/Min Air flow) "WG" 16LD Ceramic SOIC (Still Air) "GW" 16LD Ceramic SOIC (500LF/Min Air flow) "GW" 134C/W 81C/W 140C/W 90C/W JC 16LD Ceramic SOIC "WG"(Note 4) 16LD Ceramic SOIC "GW" Package Weight (Typical) 16LD Ceramic SOIC "WG" 16LD Ceramic SOIC "GW" ESD Rating (Note 7) 7C/W 15C/W 360mg 410mg 2 KV Quality Conformance Inspection Mil-Std-883, Method 5005 - Group A Subgroup Description Temp (C) 1 Static tests at +25 2 Static tests at +125 3 Static tests at -55 4 Dynamic tests at +25 5 Dynamic tests at +125 6 Dynamic tests at -55 7 Functional tests at +25 8A Functional tests at +125 8B Functional tests at -55 9 Switching tests at +25 10 Switching tests at +125 11 Switching tests at -55 12 Settling time at +25 13 Settling time at +125 14 Settling time at -55 www.national.com 4 LP2953QML LP2953A Electrical Characteristics DC Parameters The following conditions apply, unless otherwise specified. VI = 6V, IL = 1mA, CL = 2.2F, VO = 5V Feedback pin is tied to 5V Tap pin. Output pin is tied to Output Sense Pin. Symbol Parameter VO Output Voltage VO / VO Output Voltage Line Regulation VO / VO Conditions 1mA IL 250mA Output Voltage Load Regulation IGnd 1 V 2, 3 4.93 5.07 V 1, 2, 3 0.1 % 1 2, 3 (Note 8) IL = 250mA (Note 8) IL = 1mA (Note 9) IL = 50mA (Note 9) Ground Pin Current Ground Pin Current at Dropout IGnd Ground Pin Current at Shutdown ILimit Current Limit VO / PD Thermal Regulation VRef / VRef V (Note 8) IL = 100mA IL = 100mA (Note 9) IL = 250mA (Note 9) VI = 4.5V, IL = 100A (Note 9) (Note 9), (Note 12) VO = 0V (Note 10) Reference Voltage Reference Voltage Line Regulation VRef / VRef Reference Voltage Load Regulation IB FB Feedback Pin Bias Current IO Sink Output "Off" Pulldown Current (Note 11) % % 1 0.2 % 2, 3 0.16 % 1 0.2 % 2, 3 100 mV 1 150 mV 2, 3 300 mV 1 420 mV 2, 3 400 mV 1 520 mV 2, 3 600 mV 1 800 mV 2, 3 170 A 1 200 A 2, 3 2.0 mA 1 2.5 mA 2, 3 6.0 mA 1 8.0 mA 2, 3 28 mA 1 33 mA 2, 3 210 A 1 240 A 2, 3 140 A 1 500 mA 1 530 mA 2, 3 0.2 %/W 1 V 1 V 2, 3 1.205 1.255 0.1 % 1 0.2 % 2, 3 0.1 % 1 0.2 % 2, 3 0.4 % 1 0.6 % 2, 3 40 nA 1 60 nA 2, 3 30 mA 1 20 mA 2, 3 VI = 6V to 30V IRef = 0 to 200A 5 0.2 0.16 1.215 1.245 VI = 2.5V to 6V (Note 12) Subgroups 5.06 IL = 0.1mA to 1mA (Note 8) Units 4.94 IL = 1mA to 250mA IL = 50mA Max 4.975 5.025 Dropout Voltage IGnd VRef Min VI = 6V to 30V IL = 1mA VI - VO Notes www.national.com LP2953QML Dropout Detection Comparator Parameters The following conditions apply, unless otherwise specified. VI = 6V, IL = 1mA, CL = 2.2F, VO = 5V Feedback pin is tied to 5V Tap pin. Output pin is tied to Output Sense Pin. Symbol IOH VOL VTh Max VTh Min Parameter Output "High" Leakage Output "Low" Voltage Conditions Notes Min VOH = 30V (Note 13) Lower Threshold Voltage (Note 13) Units Subgroups 1.0 A 1 2, 3 2.0 A 250 mV 1 400 mV 2, 3 -320 -150 mV 1 -380 -130 mV 2 -380 -120 mV 3 -450 -280 mV 1 -640 -180 mV 2 -640 -155 mV 3 Min Max Units Subgroups -7.5 7.5 mV 1 -10 10 mV 2 -12 12 mV 3 -30 30 nA 1 -50 50 nA 2 -75 75 nA 3 Min Max Units Subgroups -7.5 7.5 mV 1 -10 10 mV 2 -12 12 mV 3 -30 30 nA 1 -50 50 nA 2 -75 75 nA 3 1.0 A 1 2.0 A 2 2.2 A 3 250 mV 1 400 mV 2 420 mV 3 VI = 4V, IO Comp = 400A Upper Threshold Voltage Max Shutdown Input Parameters The following conditions apply, unless otherwise specified. VI = 6V, IL = 1mA, CL = 2.2F, VO = 5V Feedback pin is tied to 5V Tap pin. Output pin is tied to Output Sense Pin. Symbol VIO IIB Parameter Input Offset Voltage Input Bias Current Conditions Notes Referred to VRef VI Comp = 0 to 5V Auxillary Comparator Parameters The following conditions apply, unless otherwise specified. VI = 6V, IL = 1mA, CL = 2.2F, VO = 5V Feedback pin is tied to 5V Tap pin. Output pin is tied to Output Sense Pin. Symbol VIO IIB IOH VOL Parameter Input Offset Voltage Input Bias Current Output "High" Leakage Output "Low" Voltage www.national.com Conditions Referred to VRef VI Comp = 0 to 5V VOH = 30V, VI Comp = 1.3V VI Comp = 1.1V, IO Comp = 400A 6 Notes LP2953QML DC Drift Parameters The following conditions apply, unless otherwise specified. VI = 6V, IL = 1mA, CL = 2.2F, VO = 5V Feedback pin is tied to 5V Tap pin. Output pin is tied to Output Sense Pin. calculations performed on QMLV devices at group B , subgroup 5. Symbol VI - VO IGnd Min Max Units Subgroups IL = 1mA -12 12 % 1 IL = 50mA -12 12 % 1 IL = 100mA -12 12 % 1 IL = 250mA -12 12 % 1 IL = 1mA, 5A or 10% whichever is greater -5.0 5.0 A 1 IL = 50mA, 5A or 10% whichever is greater -5.0 5.0 A 1 IL = 100mA, 5A or 10% whichever is greater -5.0 5.0 A 1 IL = 250mA, 5A or 10% whichever is greater -5.0 5.0 A 1 Parameter Dropout Voltage Ground Pin Current Conditions Notes IGnd Ground Pin Current at Dropout VI = 4.5V, IL = 100A, 5A or 10% whichever is greater -5.0 5.0 A 1 IGnd Ground Pin Current at Shutdown 5A or 10% whichever is greater -5.0 5.0 A 1 VIO Input Offset Voltage Referred to VRef Shutdown Input -1.0 1.0 mV 1 Referred to VRef Auxillary Comparator -1.0 1.0 mV 1 IIB Input Bias Current VI Comp = 0 to 5V Shutdown Input -5.0 5.0 nA 1 VI Comp = 0 to 5V Auxillary Comparator -5.0 5.0 nA 1 Note 2: Abs. Max Ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see Electrical Characteristics. The guarantees apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions. Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature), JA (package junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PDmax = (TJmax - TA)/ JA or the number given in the Absolute Maximum Ratings, whichever is lower. Note 4: The package material for these devices allows much improved heat transfer over our standard ceramic packages. In order to take full advantage of this improved heat transfer, heat sinking must be provided between the package base (directly beneath the die), and either metal traces on, or thermal vias through, the printed circuit board. Without this additional heat sinking, device power dissipation must be calculated using JA, rather than JC, thermal resistance. It must not be assumed that the device leads will provide substantial heat transfer out the package, since the thermal resistance of the leadframe material is very poor, relative to the material of the package base. The stated JC thermal resistance is for the package material only, and does not account for the additional thermal resistance between the package base and the printed circuit board. The user must determine the value of the additional thermal resistance and must combine this with the stated value for the package, to calculate the total allowed power dissipation for the device. Note 5: When used in dual-supply systems where the regulator load is returned to a negative supply, the output voltage must be diode-clamped to ground. Note 6: May exceed the input supply voltage. Note 7: Human body model, 1.5 K in series with 100 pF. Note 8: 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. At very low values of programmed output voltage, the input voltage minimum of 2V (2.3V over temperature) must be observed. Note 9: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the ground pin current, output load current, and current through the external resistive divider (if used). Note 10: Thermal regulation is the change in output voltage at a time T after a change in power dissipation, excluding load or line regulation effects. Specifications are for a 200 mA load pulse at VI = VO(Nom)+15V (3W pulse) for T = 10 mS. Note 11: VRef VO (VI - 1V), 2.3V VI 30V, 100 A IL 250 mA. Note 12: VShutdown 1.1V, VO = VO(Nom). Note 13: Comparator thresholds are expressed in terms of a voltage differential at the Feedback terminal below the nominal VRef measured at VI = VO(Nom) + 1V. To express these thresholds in terms of output voltage change, multiply by the Error amplifier gain, which is VO/ VRef = (R1 + R2)/R2 (refer to Figure 2). 7 www.national.com LP2953QML Typical Performance Characteristics Unless otherwise specified: VI = 6V, IL = 1 mA, CL = 2.2 F, VSD = 3V, TA = 25C, VO = 5V. Quiescent Current Quiescent Current 20161127 20161128 Ground Pin Current vs Load Ground Pin Current 20161130 20161129 Ground Pin Current Output Noise Voltage 20161131 www.national.com 20161132 8 LP2953QML Ripple Rejection Ripple Rejection 20161133 20161134 Ripple Rejection Line Transient Response 20161136 20161135 Line Transient Response Output Impedance 20161137 20161138 9 www.national.com LP2953QML Load Transient Response Load Transient Response 20161139 20161140 Dropout Characteristics Enable Transient 20161142 20161141 Enable Transient Short-Circuit Output Current and Maximum Output Current 20161143 20161144 www.national.com 10 LP2953QML Feedback Bias Current Feedback Pin Current 20161145 20161146 Error Output Comparator Sink Current 20161148 20161147 Divider Resistance Dropout Detection Comparator Threshold Voltages 20161149 20161150 11 www.national.com LP2953QML Thermal Regulation Minimum Operating Voltage 20161151 20161152 Dropout Voltage 20161153 www.national.com 12 HEATSINK REQUIREMENTS The maximum allowable power dissipation for the LP2953 is limited by the maximum junction temperature (+150C) and the two parameters that determine how quickly heat flows away from the die: the ambient temperature and the junctionto-ambient thermal resistance of the part. The military parts which are manufactured in ceramic DIP packages contain a KOVAR lead frame (unlike the industrial parts, which have a copper lead frame). The KOVAR material is necessary to attain the hermetic seal required in military applications. The KOVAR lead frame does not conduct heat as well as copper, which means that the PC board copper can not be used to significantly reduce the overall junction-to-ambient thermal resistance. The power dissipation calculations are done using a fixed value for (J-A), the junction-to-ambient thermal resistance, of 134C/W and can not be changed by adding copper foil patterns to the PC board. This leads to an important fact: The maximum allowable power dissipation in any application using the LP2953 is dependent only on the ambient temperature: 20161126 FIGURE 1. Power Derating Curve for LP2953 PROGRAMMING THE OUTPUT VOLTAGE The regulator may be pin-strapped for 5V operation using its internal resistive divider by tying the Output and Sense pins together and also tying the Feedback and 5V Tap pins together. Alternatively, it may be programmed for any voltage between the 1.23V reference and the 30V maximum rating using an external pair of resistors (see Figure 2). The complete equation for the output voltage is: EXTERNAL CAPACITORS A 2.2 F (or greater) capacitor is required between the output pin and ground to assure stability when the output is set to 5V. Without this capacitor, the part will oscillate. Most type of tantalum or aluminum electrolytics will work here. Film types will work, but are more expensive. Many aluminum electrolytics contain electrolytes which freeze at -30C, which requires the use of solid tantalums below -25C. The important parameters of the capacitor are an ESR of about 5 or less and a resonant frequency above 500 kHz (the ESR may increase by a factor of 20 or 30 as the temperature is reduced from 25C to -30C). The value of this capacitor may be increased without limit. At lower values of output current, less output capacitance is required for stability. The capacitor can be reduced to 0.68 F for currents below 10 mA or 0.22 F for currents below 1 mA. Programming the output for voltages below 5V runs the error amplifier at lower gains requiring more output capacitance for stability. At 3.3V output, a minimum of 4.7 F is required. For the worst-case condition of 1.23V output and 250 mA of load current, a 6.8 F (or larger) capacitor should be used. A 1 F capacitor should be placed from the input pin to ground if there is more than 10 inches of wire between the input and the AC filter capacitor or if a battery input is used. Stray capacitance to the Feedback terminal can cause instability. This problem is most likely to appear when using high value external resistors to set the output voltage. Adding a 100 pF capacitor between the Output and Feedback pins and increasing the output capacitance to 6.8 F (or greater) will cure the problem. where VREF is the 1.23V reference and IFB is the Feedback pin bias current (-20 nA typical). The minimum recommended load current of 1 A sets an upper limit of 1.2 M on the value of R2 in cases where the regulator must work with no load (see Minimim Load ). IFB will produce a typical 2% error in VO which can be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100 k will reduce this error to 0.17% while increasing the resistor program current to 12 A. Since the typical quiescent current is 120 A, this added current is negligible. 13 www.national.com LP2953QML MINIMUM LOAD When setting the output voltage using an external resistive divider, a minimum current of 1 A is recommended through the resistors to provide a minimum load. It should be noted that a minimum load current is specified in several of the electrical characteristic test conditions, so this value must be used to obtain correlation on these tested limits. Application Hints LP2953QML 20161110 * In shutdown mode, ERROR will go high if it has been pulled up to an external supply. To avoid this invalid response, pull up to regulator output. ** Exact value depends on dropout voltage. (See Application Hints) 20161109 * See Application Hints ** Drive with TTL-low to shut down FIGURE 3. ERROR Output Timing FIGURE 2. Adjustable Regulator OUTPUT ISOLATION The regulator output can be left connected to an active voltage source (such as a battery) with the regulator input power shut off, as long as the regulator ground pin is connected to ground. If the ground pin is left floating, damage to the regulator can occur if the output is pulled up by an external voltage source. DROPOUT VOLTAGE The dropout voltage of the regulator is defined as the minimum input-to-output voltage differential required for the output voltage to stay within 100 mV of the output voltage measured with a 1V differential. The dropout voltage is independent of the programmed output voltage. REDUCING OUTPUT NOISE In reference applications it may be advantageous to reduce the AC noise present on the output. One method is to reduce regulator bandwidth by increasing output capacitance. This is relatively inefficient, since large increases in capacitance are required to get significant improvement. Noise can be reduced more effectively by a bypass capacitor placed across R1 (refer to Figure 2). The formula for selecting the capacitor to be used is: DROPOUT DETECTION COMPARATOR This comparator produces a logic "LOW" whenever the output falls out of regulation by more than about 5%. This figure results from the comparator's built-in offset of 60 mV divided by the 1.23V reference (refer to block diagrams on page 1). The 5% low trip level remains constant regardless of the programmed output voltage. An out-of-regulation condition can result from low input voltage, current limiting, or thermal limiting. Figure 3 gives a timing diagram showing the relationship between the output voltage, the ERROR output, and input voltage as the input voltage is ramped up and down to a regulator programmed for 5V output. The ERROR signal becomes low at about 1.3V input. It goes high at about 5V input, where the output equals 4.75V. Since the dropout voltage is load dependent, the input voltage trip points will vary with load current. The output voltage trip point does not vary. The comparator has an open-collector output which requires an external pull-up resistor. This resistor may be connected to the regulator output or some other supply voltage. Using the regulator output prevents an invalid "HIGH" on the comparator output which occurs if it is pulled up to an external voltage while the regulator input voltage is reduced below 1.3V. In selecting a value for the pull-up resistor, note that while the output can sink 400 A, this current adds to battery drain. Suggested values range from 100 k to 1 M. This resistor is not required if the output is unused. When VIN 1.3V, the error flag pin becomes a high impedance, allowing the error flag voltage to rise to its pull-up voltage. Using VOUT as the pull-up voltage (rather than an external 5V source) will keep the error flag voltage below 1.2V (typical) in this condition. The user may wish to divide down the error flag voltage using equal-value resistors (10 k suggested) to ensure a low-level logic signal during any fault condition, while still allowing a valid high logic level during normal operation. www.national.com This gives a value of about 0.1 F. When this is used, the output capacitor must be 6.8 F (or greater) to maintain stability. The 0.1 F capacitor reduces the high frequency gain of the circuit to unity, lowering the output noise from 260 V to 80 V using a 10 Hz to 100 kHz bandwidth. Also, noise is no longer proportional to the output voltage, so improvements are more pronounced at high output voltages. AUXILIARY COMPARATOR The LP2953 contains an auxiliary comparator whose inverting input is connected to the 1.23V reference. The auxiliary comparator has an open-collector output whose electrical characteristics are similar to the dropout detection comparator. The non-inverting input and output are brought out for external connections. SHUTDOWN INPUT A logic-level signal will shut off the regulator output when a "LOW" (<1.2V) is applied to the Shutdown input. To prevent possible mis-operation, the Shutdown input must be actively terminated. If the input is driven from open-collector logic, a pull-up resistor (20 k to 100 k recommended) should be connected from the Shutdown input to the regulator input. 14 ground, the reverse-battery protection feature which protects the regulator input is sacrificed if the Shutdown input is tied directly to the regulator input. If reverse-battery protection is required in an application, the pull-up resistor between the Shutdown input and the regulator input must be used. 15 www.national.com LP2953QML If the Shutdown input is driven from a source that actively pulls high and low (like an op-amp), the pull-up resistor is not required, but may be used. If the shutdown function is not to be used, the cost of the pullup resistor can be saved by simply tying the Shutdown input directly to the regulator input. IMPORTANT: Since the Absolute Maximum Ratings state that the Shutdown input can not go more than 0.3V below LP2953QML Typical Applications Basic 5V Regulator 20161115 5V Current Limiter with Load Fault Indicator 20161116 * Output voltage equals +VIN minum dropout voltage, which varies with output current. Current limits at a maximum of 380 mA (typical). ** Select R1 so that the comparator input voltage is 1.23V at the output voltage which corresponds to the desired fault current value. www.national.com 16 LP2953QML Low T.C. Current Sink 20161117 5V Regulator with Error Flags for LOW BATTERY and OUT OF REGULATION 20161118 * Connect to Logic or P control inputs. LOW BATT flag warns the user that the battery has discharged down to about 5.8V, giving the user time to recharge the battery or power down some hardware with high power requirements. The output is still in regulation at this time. OUT OF REGULATION flag indicates when the battery is almost completely discharged, and can be used to initiate a power-down sequence. 17 www.national.com LP2953QML 5V Battery Powered Supply with Backup and Low Battery Flag 20161119 The circuit switches to the NI-CAD backup battery when the main battery voltage drops below about 5.6V, and returns to the main battery when its voltage is recharged to about 6V. The 5V MAIN output powers circuitry which requires no backup, and the 5V MEMORY output powers critical circuitry which can not be allowed to lose power. * The BATTERY LOW flag goes low whenever the circuit switches to the NI-CAD backup battery. 5V Regulator with Timed Power-On Reset 20161120 Timing Diagram for Timed Power-On Reset 20161121 * RT = 1 MEG, CT = 0.1 F www.national.com 18 LP2953QML 5V Regulator with Error Flags for LOW BATTERY and OUT OF REGULATION with SNAP-ON/SNAP-OFF Output 20161123 * Connect to Logic or P control inputs. OUTPUT has SNAP-ON/SNAP-OFF feature. LOW BATT flag warns the user that the battery has discharged down to about 5.8V, giving the user time to recharge the battery or shut down hardware with high power requirements. The output is still in regulation at this time. OUT OF REGULATION flag goes low if the output goes below about 4.7V, which could occur from a load fault. OUTPUT has SNAP-ON/SNAP-OFF feature. Regulator snaps ON at about 5.7V input, and OFF at about 5.6V. 5V Regulator with Timed Power-On Reset, Snap-On/Snap-Off Feature and Hysteresis 20161124 Timing Diagram 20161125 Td = (0.28) RC = 28 ms for components shown. 19 www.national.com LP2953QML Revision History Section Released Revision Section Changes 11/30/2010 A New Release, Corporate format 1 MDS data sheet converted into one Corp. data sheet format. MNLP2953AM-X Rev 1A1 will be archived. 09/01/2011 B Ordering Information, Absolute Maximum Ratings Ordering Information -- entered new 'GW' devices. Absolute Maximum Ratings -- added new Theta JA and Theta JC numbers. LP2953QML Rev A will be archived. www.national.com 20 LP2953QML Physical Dimensions inches (millimeters) unless otherwise noted 16-Pin Ceramic Surface-Mount NS Package Number WG16A 21 www.national.com LP2953QML Adjustable Micropower Low-Dropout Voltage Regulators Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH(R) Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise(R) Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagicTM www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise(R) Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION ("NATIONAL") PRODUCTS. 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