LP2950,LP2951 LP2950/LP2951 Series of Adjustable Micropower Voltage Regulators Literature Number: SNVS764M LP2950/LP2951 Series of Adjustable Micropower Voltage Regulators General Description The LP2950 and LP2951 are micropower voltage regulators with very low quiescent current (75A typ.) and very low dropout voltage (typ. 40mV at light loads and 380mV at 100mA). They are ideally suited for use in battery-powered systems. Furthermore, the quiescent current of the LP2950/ LP2951 increases only slightly in dropout, prolonging battery life. The LP2950-5.0 is available in the surface-mount D-Pak package, and in the popular 3-pin TO-92 package for pincompatibility with older 5V regulators. The 8-lead LP2951 is available in plastic, ceramic dual-in-line, LLP, or metal can packages and offers additional system functions. One such feature is an error flag output which warns of a low output voltage, often due to falling batteries on the input. It may be used for a power-on reset. A second feature is the logic-compatible shutdown input which enables the regulator to be switched on and off. Also, the part may be pin-strapped for a 5V, 3V, or 3.3V output (depending on the version), or programmed from 1.24V to 29V with an external pair of resistors. Careful design of the LP2950/LP2951 has minimized all contributions to the error budget. This includes a tight initial tolerance (.5% typ.), extremely good load and line regulation (.05% typ.) and a very low output voltage temperature coefficient, making the part useful as a low-power voltage reference. Features 5V, 3V, and 3.3V versions available High accuracy output voltage Guaranteed 100mA output current Extremely low quiescent current Low dropout voltage Extremely tight load and line regulation Very low temperature coefficient Use as Regulator or Reference Needs minimum capacitance for stability Current and Thermal Limiting Stable with low-ESR output capacitors (10m to 6) LP2951 versions only Error flag warns of output dropout Logic-controlled electronic shutdown Output programmable from 1.24 to 29V Block Diagram and Typical Applications LP2950 854625 (c) 2011 National Semiconductor Corporation 8546 www.national.com LP2950/LP2951 Series of Adjustable Micropower Voltage Regulators August 20, 2011 LP2950/LP2951 LP2951 854601 10-Lead Ceramic Surface-Mount Package (WG) Connection Diagrams TO-92 Plastic Package (Z) 854602 Bottom View 854664 Top View Dual-In-Line Packages (N, J) Surface-Mount Package (M, MM) TO-252 (D-Pak) 854626 Top View 854670 Front View Metal Can Package (H) 8-Lead LLP 854671 Connect DAP to GND at device pin 4. 854619 Top View Top View www.national.com 2 Package TO-92 (Z) TO-252 (D-Pak) Temperature Range VOUT Part Number Package Marking Transport Media NSC Drawing -40 < TJ < 125 3.0 LP2950ACZ-3.0 2950A CZ3.0 Bag Z03A LP2950CZ-3.0 2950 CZ3.0 Bag 3.3 LP2950ACZ-3.3 2950A CZ3.3 Bag LP2950CZ-3.3 2950 CZ3.3 Bag 5.0 LP2950ACZ-5.0 2950A CZ5.0 Bag LP2950CZ-5.0 2950 CZ5.0 Bag 3.0 LP2950CDT-3.0 LP2950CDT-3.0 75 Units/Rail -40 < TJ < 125 LP2950CDTX-3.0 3.3 LP2950CDT-3.3 LP2950CDT-3.3 LP2950CDTX-3.3 5.0 LP2950CDT-5.0 -40 < TJ < 125 3.0 3.3 5.0 M (M08A) -40 < TJ < 125 3.0 LP2950CDT-5.0 40 Units/Rail LP2951CN-3.0 LP2951CN-3.0 40 Units/Rail LP2951ACN-3.3 LP2951ACN-3.3 40 Units/Rail LP2951CN-3.3 LP2951CN-3.3 40 Units/Rail LP2951ACN LP2951ACN 40 Units/Rail LP2951CN LP2951CN 40 Units/Rail LP2951ACM-3.0 2951ACM30* (where * is die rev letter) 2.5k Units Tape and Reel LP2951CMX-3.0 LP2951ACM-3.3 LP2951ACMX-3.3 LP2951CM-3.3 LP2951CMX-3.3 LP2951ACM 3.0 2951CM30* (where * is die rev letter) 2.5k Units Tape and Reel 2951ACM33* (where * is die rev letter) 2.5k Units Tape and Reel 2951CM33* (where * is die rev letter) 2.5k Units Tape and Reel 2.5k Units Tape and Reel LP2951ACMM-3.0 L0BA 1k Units Tape and Reel 95 Units/Rail 95 Units/Rail MUA08A 3.5k Units Tape and Reel L0BB LP2951CMMX-3.0 1k Units Tape and Reel 3.5k Units Tape and Reel LP2951ACMM-3.3 L0CA LP2951ACMMX-3.3 1k Units Tape and Reel 3.5k Units Tape and Reel LP2951CMM-3.3 L0CB LP2951CMMX-3.3 5.0 95 Units/Rail LP2951CMX LP2951CMM-3.0 3.3 M08A 95 Units/Rail 2.5k Units Tape and Reel LP2951ACMMX-3.0 N08E 95 Units/Rail 2951CM* (where * is die rev letter) LP2951CM -40 < TJ < 125 95 Units/Rail 2951ACM* (where * is die rev letter) LP2951ACMX MM (MUA08A) 2.5k Units Tape and Reel LP2951ACN-3.0 LP2951CM-3.0 5.0 75 Units/Rail LP2951ACN-3.0 LP2951ACMX-3.0 3.3 75 Units/Rail 2.5k Units Tape and Reel LP2950CDTX-5.0 N (N-08E) TD03B 2.5k Units Tape and Reel 1k Units Tape and Reel 3.5k Units Tape and Reel LP2951ACMM L0DA LP2951ACMMX 1k Units Tape and Reel 3.5k Units Tape and Reel LP2951CMM L0DB LP2951CMMX 1k Units Tape and Reel 3.5k Units Tape and Reel J (J08A) -55 < TJ < 150 5.0 LP2951J/883 See MIL/AERO Datasheet 40 Units/Rail J08A H (H08C) -55 < TJ < 150 5.0 LP2951H/883 See MIL/AERO Datasheet Tray H08C WG (WG10A) -55 < TJ < 150 5.0 LP2951WG/883 See MIL/AERO Datasheet Tray WG10A 3 www.national.com LP2950/LP2951 Ordering Information LP2950/LP2951 Package Temperature Range VOUT 8-lead LLP -40 < TJ < 125 3.0 Part Number Package Marking LP2951ACSD-3.0 51AC30 LP2951ACSDX-3.0 LP2951CSD-3.0 51AC30B LP2951ACSD-3.3 51AC33 SDC08A 1k Units Tape and Reel 1k Units Tape and Reel 4.5k Units Tape and Reel LP2951CSD-3.3 51AC33B LP2951CSDX-3.3 1k Units Tape and Reel 4.5k Units Tape and Reel LP2951ACSD 2951AC LP2951ACSDX 1k Units Tape and Reel 4.5k Units Tape and Reel LP2951CSD 2951ACB LP2951CSDX www.national.com 1k Units Tape and Reel 4.5k Units Tape and Reel LP2951ACSDX-3.3 5.0 NSC Drawing 4.5k Units Tape and Reel LP2951CSDX-3.0 3.3 Transport Media 1k Units Tape and Reel 4.5k Units Tape and Reel 4 If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Input Supply Voltage SHUTDOWN Input Voltage, Error Comparator Output Voltage, (Note 9) FEEDBACK Input Voltage (Note 9, Note 10) Power Dissipation Junction Temperature (TJ) Ambient Storage Temperature Soldering Dwell Time, Temperature Wave Infrared Vapor Phase Operating Ratings (Note 1) Maximum Input Supply Voltage Junction Temperature Range (TJ) (Note 8) LP2950AC-XX, LP2950C-XX LP2951 LP2951AC-XX, LP2951C-XX -0.3 to +30V -1.5 to +30V 30V -40 to +125C -55 to +150C -40 to +125C Internally Limited +150C -65 to +150C 4 seconds, 260C 10 seconds, 240C 75 seconds, 219C Electrical Characteristics (Note 2) LP2951 Conditions (Note 2) Parameter 2500V Typ LP2950AC-XX LP2951AC-XX Tested Limit (Note 3) (Note 16) Typ Tested Design Limit Limit (Note 3) (Note 4) LP2950C-XX LP2951C-XX Typ Tested Design Limit Limit (Note 3) (Note 4) Units 3V Versions (Note 17) Output Voltage TJ = 25C 3.0 3.015 -25C TJ 85C 3.0 2.955 V min Full Operating Temperature Range 3.0 3.036 2.964 3.0 3.036 2.964 3.0 3.060 2.940 V max V min 100A IL 100mA 3.0 3.045 3.0 3.042 3.0 3.072 V max 2.928 V min 3.0 2.985 3.015 3.0 2.985 TJ TJMAX 2.955 V min 3.045 3.0 2.970 Output Voltage V max 2.970 3.030 3.0 3.030 2.958 V max 3.3V Versions (Note 17) Output Voltage TJ = 25C 3.3 3.317 3.3 3.284 -25C TJ 85C 3.317 3.3 3.284 3.3 3.333 3.3 3.333 V max 3.267 V min 3.3 3.267 Output Voltage 3.350 V max 3.251 V min Full Operating Temperature Range 3.3 3.340 3.260 3.3 3.340 3.260 3.3 3.366 3.234 V max V min 100A IL 100mA 3.3 3.350 3.3 3.346 3.3 3.379 V max 3.221 V min TJ TJMAX 3.251 3.254 5V Versions (Note 17) Output Voltage TJ = 25C 5.0 5.025 5.0 4.975 -25C TJ 85C 5.025 5.0 4.975 5.0 5.0 5.05 5.0 4.95 Output Voltage 5.05 V max 4.95 V min 5.075 V max 4.925 V min Full Operating Temperature Range 5.0 5.06 4.94 5.0 5.06 4.94 5.0 5.1 4.9 V max V min 100A IL 100mA 5.0 5.075 5.0 5.075 5.0 5.12 V max 4.88 V min TJ TJMAX 4.925 4.925 5 www.national.com LP2950/LP2951 ESD Rating Human Body Model(Note 18) Absolute Maximum Ratings (Note 1) LP2950/LP2951 LP2951 Parameter Conditions (Note 2) Typ LP2950AC-XX LP2951AC-XX Tested Limit (Note 3) (Note 16) Typ Tested Design Limit Limit (Note 3) (Note 4) LP2950C-XX LP2951C-XX Typ Tested Design Limit Limit (Note 3) (Note 4) Units All Voltage Options Output Voltage Temperature Coefficient (Note 12) Line Regulation (Note 14) (VONOM + 1)V Vin 0.03 Load Regulation (Note 14) Dropout Voltage (Note 5) 20 30V (Note 15) 100A IL 100mA 0.04 IL = 100A IL = 100A 20 0.1 0.5 0.03 0.1 0.3 0.04 0.1 50 380 450 600 380 75 120 75 8 0.1 80 150 ppm/C 0.4 % max % max 0.3 % max % max 150 mV max mV max 600 mV max mV max 0.2 0.2 80 150 50 600 380 450 450 120 75 12 8 12 A max 120 140 14 110 0.04 0.1 140 IL = 100mA 50 0.2 50 Current 100 0.2 80 150 IL = 100mA Ground 120 140 8 12 mA max 14 170 110 170 160 200 0.05 0.2 14 170 160 200 0.05 0.2 mA max A max Dropout Vin = (VONOM - 0.5) V Ground Current IL = 100A Current Limit Vout = 0 160 Thermal Regulation (Note 13) 0.05 Output Noise, CL = 1F (5V Only) 430 430 430 V rms 10 Hz to 100 kHz CL = 200F 160 160 160 V rms 100 100 100 V rms 200 110 A max 200 200 220 200 220 0.2 A max mA max 220 mA max %/W max CL = 3.3F (Bypass = 0.01F Pins 7 to 1 (LP2951) 8-pin Versions Only LP2951 Reference 1.23 5 Voltage Reference Voltage Feedback Pin Bias Current Temperature Coefficient www.national.com 1.23 5 1.26 1.22 1.2 (Note 7) Feedback Pin Bias Current Reference Voltage Temperature Coefficient LP2951AC-XX 1.25 LP2951C-XX 1.23 5 1.26 40 60 20 V max 1.2 1.2 V max V min V min 1.27 1.19 1.285 1.185 V max V min 60 nA max nA max 1.26 1.27 1.22 1.27 1.19 20 (Note 12) 1.25 1.21 40 20 60 40 20 20 50 ppm/C 0.1 0.1 0.1 nA/C 6 Parameter Conditions (Note 2) Typ LP2950AC-XX LP2951AC-XX Tested Limit (Note 3) (Note 16) Typ LP2950C-XX LP2951C-XX Tested Design Limit Limit (Note 3) (Note 4) Typ Tested Design Limit Limit (Note 3) (Note 4) Units Error Comparator Output Leakage 0.01 1 Output Low Vin = (VONOM - 0.5) V 150 250 Voltage IOL = 400A Upper Threshold Voltage (Note 6) Lower Threshold Voltage (Note 6) 75 Hysteresis (Note 6) 15 15 15 mV 1.3 1.3 1.3 V V max V min Current 0.01 1 150 250 2 1 150 250 2 400 60 0.01 A max VOH = 30V 400 40 25 60 95 140 75 40 60 75 mV max 400 mV max 25 mV min mV min 140 mV max mV max 40 25 95 A max 2 95 140 Shutdown Input Input Logic Voltage Shutdown Pin Input Current Low (Regulator ON) High (Regulator OFF) Vshutdown = 2.4V 0.6 2.0 30 0.7 2.0 50 30 50 100 Vshutdown = 30V 450 (Note 11) 3 30 600 450 600 100 450 3 20 10 750 3 20 A max A max 600 750 10 A max 50 100 750 Regulator Output Current in Shutdown 0.7 2.0 A max A max 10 20 A max Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may 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: Unless otherwise specified all limits guaranteed for VIN = (VONOM + 1)V, IL = 100A and CL = 1F for 5V versions and 2.2F for 3V and 3.3V versions. Limits appearing in boldface type apply over the entire junction temperature range for operation. Limits appearing in normal type apply for TA = TJ = 25C. Additional conditions for the 8-pin versions are FEEDBACK tied to VTAP, OUTPUT tied to SENSE, and VSHUTDOWN 0.8V. Note 3: Guaranteed and 100% production tested. Note 4: Guaranteed but not 100% production tested. These limits are not used to calculate outgoing AQL levels. Note 5: Dropout Voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential. At very low values of programmed output voltage, the minimum input supply voltage of 2V (2.3V over temperature) must be taken into account. Note 6: Comparator thresholds are expressed in terms of a voltage differential at the Feedback terminal below the nominal reference voltage measured at Vin = (VONOM + 1)V. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = Vout/Vref = (R1 + R2)/R2.For example, at a programmed output voltage of 5V, the Error output is guaranteed to go low when the output drops by 95mV x 5V/1.235V = 384 mV. Thresholds remain constant as a percent of Vout as Vout is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed. Note 7: Vref Vout (Vin - 1V), 2.3V Vin 30V, 100A IL 100mA, TJ TJMAX. Note 8: The junction-to-ambient thermal resistances are as follows: 180C/W and 160C/W for the TO-92 package with 0.40 inch and 0.25 inch leads to the printed circuit board (PCB) respectively, 105C/W for the molded plastic DIP (N), 130C/W for the ceramic DIP (J), 160C/W for the molded plastic SOP (M), 200 C/W for the molded plastic MSOP (MM), and 160C/W for the metal can package (H). The above thermal resistances for the N, J, M, and MM packages apply when the package is soldered directly to the PCB. Junction-to-case thermal resistance for the H package is 20C/W. Junction-to-case thermal resistance for the TO-252 package is 5.4C/W. The value of JA for the LLP package is typically 51C/W but is dependent on the PCB trace area, trace material, and the number of layers and thermal vias. For details of thermal resistance and power dissipation for the LLP package, refer to Application Note AN-1187. Note 9: May exceed input supply voltage. Note 10: When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diode-clamped to ground. Note 11: Vshutdown 2V, Vin 30V, Vout = 0, Feedback pin tied to VTAP. Note 12: Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Note 13: Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 50mA load pulse at VIN = 30V (1.25W pulse) for T = 10ms. Note 14: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are covered under the specification for thermal regulation. Note 15: Line regulation for the LP2951 is tested at 150C for IL = 1mA. For IL = 100A and TJ = 125C, line regulation is guaranteed by design to 0.2%. See Typical Performance Characteristics for line regulation versus temperature and load current. 7 www.national.com LP2950/LP2951 LP2951 LP2950/LP2951 Note 16: A Military RETS specification is available on request. At time of printing, the LP2951 RETS specification complied with the boldface limits in this column. The LP2951H, WG, or J may also be procured as Standard Military Drawing Spec #5962-3870501MGA, MXA, or MPA. Note 17: All LP2950 devices have the nominal output voltage coded as the last two digits of the part number. In the LP2951 products, the 3.0V and 3.3V versions are designated by the last two digits, but the 5V version is denoted with no code at this location of the part number (refer to ordering information table). Note 18: Human Body Model (HBM) is 1.5k in series with 100pF; LP2950 passes 2.5 kV(HBM) ESD; LP2951 passes 2.5 kV(HBM) except: Feedback pin passes 1kV(HBM) and Shutdown pin passes 2kV(HBM). www.national.com 8 LP2950/LP2951 Typical Performance Characteristics Quiescent Current Dropout Characteristics 854628 854627 Input Current Input Current 854629 854630 Output Voltage vs. Temperature of 3 Representative Units Quiescent Current 854632 854631 9 www.national.com LP2950/LP2951 Quiescent Current Quiescent Current 854633 854634 Quiescent Current Short Circuit Current 854635 854636 Dropout Voltage Dropout Voltage 854638 854637 www.national.com 10 LP2950/LP2951 LP2951 Minimum Operating Voltage LP2951 Feedback Bias Current 854639 854640 LP2951 Feedback Pin Current LP2951 Error Comparator Output 854642 854641 LP2951 Comparator Sink Current Line Transient Response 854643 854644 11 www.national.com LP2950/LP2951 Load Transient Response Load Transient Response 854645 854646 LP2951 Enable Transient Output Impedance 854648 854647 Ripple Rejection Ripple Rejection 854649 www.national.com 854650 12 LP2950/LP2951 Ripple Rejection LP2951 Output Noise 854651 854652 LP2951 Divider Resistance Shutdown Threshold Voltage 854653 854654 Line Regulation LP2951 Maximum Rated Output Current 854656 854655 13 www.national.com Thermal Response 854657 854658 Output Capacitor ESR Range LP2951 Input Pin Current vs Input Voltage INPUT PIN CURRENT, IIN (A) 120 VSD = 2.0V Output Load = Open 100 80 60 40 Ta= -50C Ta= -40C Ta= +25C Ta= +125C 20 0 0 LP2951 Input Pin Current vs Input Voltage 120 VSD = 2.0V Output Load = Short to Ground 100 80 60 40 Ta= -50C Ta= -40C Ta= +25C Ta= +125C 20 0 0 5 10 15 20 25 INPUT PIN VOLTAGE, VIN (V) 30 854673 www.national.com 5 10 15 20 25 INPUT PIN VOLTAGE, VIN (V) 30 854672 854663 INPUT PIN CURRENT, IIN (A) LP2950/LP2951 LP2950 Maximum Rated Output Current 14 OUTPUT CAPACITOR REQUIREMENTS A 1.0 F (or greater) capacitor is required between the output and ground for stability at output voltages of 5V or higher. At lower output voltages, more capacitance is required (2. 2F or more is recommended for 3.0V and 3.3V versions). Without this capacitor the part will oscillate. Most types of tantalum or aluminum electrolytic work fine here; even film types work but are not recommended for reasons of cost. Many aluminum electrolytics have electrolytes that freeze at about -30C, so solid tantalums are recommended for operation below -25 C. The important parameters of the capacitor are an ESR of about 5 or less and a resonant frequency above 500 kHz. The value of this capacitor may be increased without limit. 1) At power-up, with the input voltage rising faster than output stage can charge the output capacitor. VIN tRISE(MIN) > ((COUT / 100 mA) x VIN) Where VIN = VOUT(NOM) + 1.0V 2) Recovery from an output short circuit to ground condition. 854663 COUT(MIN) (160 mA - ILOAD(NOM))/((VOUT(NOM)/10)/25 s)) FIGURE 1. Output Capacitor ESR Range The reason for the lower ESR limit is that the loop compensation of the feedback loop relies on the capacitance value and the ESR value of the output capacitor to provide the zero that gives added phase lead (See Figure 1). 3) Toggling the LP2951 SHUTDOWN pin from high (i.e. OFF) to low (i.e. ON). COUT(MIN) (160 mA - ILOAD(NOM))/((VOUT(NOM)/10)/25 s)) fZ = (1 / (2 x x COUT x ESR) ) Using the 2.2 F value from the Output Capacitor ESR Range curve (Figure 1), a useful range for fZ can be estimated: fZ(MIN)= (1 / (2 x x 2.2 F x 5) ) = 14.5 kHz fZ(MAX)= (1 / (2 x x 2.2 F x 0.05) ) = 318 kHz For ceramic capacitors, the low ESR produces a zero at a frequency that is too high to be useful, so meaningful phase lead does not occur. A ceramic output capacitor can be used if a series resistance is added (recommended value of resistance about 0.1 to 2) to simulate the needed ESR. Only X5R, X7R, or better, MLCC types should be used, and should have a DC voltage rating at least twice the VOUT(NOM) value. At lower values of output current, less output capacitance is required for stability. The capacitor can be reduced to 0.33 F for currents below 10 mA or 0.1 F for currents below 1 mA. Using the adjustable versions at voltages below 5V runs the error amplifier at lower gains so that more output capacitance is needed. For the worst-case situation of a 100mA load at 1.23V output (Output shorted to Feedback) a 3.3 F (or greater) capacitor should be used. Unlike many other regulators, the LP2950 will remain stable and in regulation with no load in addition to the internal voltage divider. This is especially important in CMOS RAM keep-alive applications. When setting the output voltage of the LP2951 854647 FIGURE 2. LP2951 Enable Transient INPUT CAPACITOR REQUIREMENTS A minimum 1 F tantalum, ceramic or aluminum electrolytic capacitor should be placed from the LP2950/LP2951 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 is used as the input. ERROR DETECTION COMPARATOR OUTPUT The comparator produces a logic low output whenever the LP2951 output falls out of regulation by more than approximately 5%. This figure is the comparator's built-in offset of about 60mV divided by the 1.235 reference voltage. (Refer to 15 www.national.com LP2950/LP2951 versions with external resistors, a minimum load of 1 A is recommended. Applications having conditions that may drive the LP2950/51 into nonlinear operation require special consideration. Nonlinear operation will occur when the output voltage is held low enough to force the output stage into output current limiting while trying to pull the output voltage up to the regulated value. The internal loop response time will control how long it takes for the device to regain linear operation when the output has returned to the normal operating range. There are three significant nonlinear conditions that need to be considered, all can force the output stage into output current limiting mode, all can cause the output voltage to over-shoot with low value output capacitors when the condition is removed, and the recommended generic solution is to set the output capacitor to a value not less than 10 F. Although the 10 F value for COUT may not eliminate the output voltage over-shoot in all cases, it should lower it to acceptable levels (<10% of VOUT(NOM)) in the majority of cases. In all three of these conditions, applications with lighter load currents are more susceptible to output voltage over-shoot than applications with higher load currents. Application Hints LP2950/LP2951 the block diagram in the front of the datasheet.) This trip level remains "5% below normal" regardless of the programmed output voltage of the 2951. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V for a 12V output. The out of regulation condition may be due either to low input voltage, current limiting, or thermal limiting. Figure 3 below gives a timing diagram depicting the ERROR signal and the regulated output voltage as the LP2951 input is ramped up and down. For 5V versions, the ERROR signal becomes valid (low) at about 1.3V input. It goes high at about 5V input (the input voltage at which VOUT = 4.75V). Since the LP2951's dropout voltage is load-dependent (see curve in typical performance characteristics), the input voltage trip point (about 5V) will vary with the load current. The output voltage trip point (approx. 4.75V) does not vary with load. The error comparator has an open-collector output which requires an external pull up resistor. This resistor may be returned to the output or some other supply voltage depending on system requirements. In determining a value for this resistor, note that while the output is rated to sink 400A, this sink current adds to battery drain in a low battery condition. Suggested values range from 100k to 1 M. The resistor is not required if this output is unused. produce a 2% typical error in VOUT which may be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100 k reduces this error to 0.17% while increasing the resistor program current to 12 A. Since the LP2951 typically draws 60 A at no load with Pin 2 open-circuited, this is a small price to pay. 854607 *See Application Hints **Drive with TTL-high to shut down. Ground or leave open if shutdown feature is not to be used. Note: Pins 2 and 6 are left open. FIGURE 4. Adjustable Regulator Stray capacitance to the LP2951 Feedback terminal can cause instability. This may especially be a problem when using high value external resistors to set the output voltage. Adding a 100 pF capacitor between the Output pin and the Feedback pin,and increasing the output capacitor to at least 3.3 F, will fix this problem. 854620 *When VIN 1.3V, the error flag pin becomes a high impedance, and the error flag voltage rises to its pull-up voltage. Using VOUT as the pull-up voltage (see Figure 4), rather than an external 5V source, will keep the error flag voltage under 1.2V (typ.) in this condition. The user may wish to divide down the error flag voltage using equal-value resistors (10k suggested), to ensure a low-level logic signal during any fault condition, while still allowing a valid high logic level during normal operation. REDUCING OUTPUT NOISE In reference applications it may be advantageous to reduce the AC noise present at the output. One method is to reduce the regulator bandwidth by increasing the size of the output capacitor. This is the only way noise can be reduced on the 3 lead LP2950 but is relatively inefficient, as increasing the capacitor from 1 F to 220 F only decreases the noise from 430 V(RMS) to 160 V(RMS) for a 100 kHz bandwidth at 5V output. Noise can be reduced fourfold by a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick FIGURE 3. ERROR Output Timing PROGRAMMING THE OUTPUT VOLTAGE (LP2951) The LP2951 may be pin-strapped for the nominal fixed output voltage using its internal voltage divider by tying the output and sense pins together, and also tying the feedback and VTAP pins together. Alternatively, it may be programmed for any output voltage between its 1.235V reference and its 30V maximum rating. As seen in Figure 4, an external pair of resistors is required. The complete equation for the output voltage is or about 0.01 F. When doing this, the output capacitor must be increased to 3.3 F to maintain stability. These changes reduce the output noise from 430V to 100V rms for a 100 kHz bandwidth at 5V output. With the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages. where VREF is the nominal 1.235V reference voltage and IFB is the feedback pin bias current, nominally -20nA. The minimum recommended load current of 1 A forces an upper limit of 1.2 M on the value of R2, if the regulator must work with no load (a condition often found in CMOS in standby). IFB will www.national.com 16 Board Type Thermal Vias JC JA JEDEC 2-Layer JESD 51-3 None 14.2C/W 185C/W 1 14.2C/W 68C/W 2 14.2C/W 60C/W 4 14.2C/W 51C/W 6 14.2C/W 48C/W JEDEC 4-Layer JESD 51-7 17 www.national.com LP2950/LP2951 connection). The DAP must not be connected to any potential other than ground. For the LP2951 in the SDC08A 8-Lead LLP package, the junction-to-case thermal rating, JC, is 14.2C/W, where the case is the bottom of the package at the center of the DAP. The junction-to-ambient thermal performance for the LP2951 in the SDC08A 8-Lead LLP package, using the JEDEC JESD51 standards is summarized in the following table: LLP MOUNTING The SDC08A (No Pullback) 8-Lead LLP package requires specific mounting techniques which are detailed in National Semiconductor Application Note # 1187. Referring to the section PCB Design Recommendations in AN-1187 (Page 5), it should be noted that the pad style which should be used with the LLP package is the NSMD (non-solder mask defined) type. Additionally, it is recommended the PCB terminal pads to be 0.2 mm longer than the package pads to create a solder fillet to improve reliability and inspection. The thermal dissipation of the LLP package is directly related to the printed circuit board construction and the amount of additional copper area connected to the DAP. The DAP (exposed pad) on the bottom of the LLP package is connected to the die substrate with a conductive die attach adhesive. The DAP has no direct electrical (wire) connection to any of the eight pins. There is a parasitic PN junction between the die substrate and the device ground. As such, it is strongly recommend that the DAP be connected directly to the ground at device lead 4 (i.e. GND). Alternately, but not recommended, the DAP may be left floating (i.e. no electrical LP2950/LP2951 Typical Applications 1A Regulator with 1.2V Dropout 854622 300mA Regulator with 0.75V Dropout Wide Input Voltage Range Current Limiter 854621 854609 *Minimum input-output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 160mA. Low Drift Current Source 5 Volt Current Limiter 854610 *Minimum input-output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 160mA. 854608 www.national.com 18 LP2950/LP2951 Regulator with Early Warning and Auxiliary Output Latch Off When Error Flag Occurs 854612 854611 Early warning flag on low input voltage Main output latches off at lower input voltages Battery backup on auxiliary output Operation: Reg. #1's VOUT is programmed one diode drop above 5V. Its error flag becomes active when VIN 5.7V. When VIN drops below 5.3V, the error flag of Reg. #2 becomes active and via Q1 latches the main output off. When VIN again exceeds 5.7V Reg. #1 is back in regulation and the early warning signal rises, unlatching Reg. #2 via D3. 2 Ampere Low Dropout Regulator 854613 For 5Vout, use internal resistors. Wire pin 6 to 7, & wire pin 2 to +Vout Bus. 19 www.national.com LP2950/LP2951 Open Circuit Detector for 4 20mA Current Loop 5V Regulator with 2.5V Sleep Function 854615 854614 *High input lowers Vout to 2.5V Regulator with State-of-Charge Indicator 854616 *Optional Latch off when drop out occurs. Adjust R3 for C2 Switching when Vin is 6.0V. **Outputs go low when VIN drops below designated thresholds. www.national.com 20 LP2950/LP2951 Low Battery Disconnect 854617 For values shown, Regulator shuts down when Vin < 5.5V and turns on again at 6.0V. Current drain in disconnected mode is 150A. *Sets disconnect Voltage **Sets disconnect Hysteresis System Overtemperature Protection Circuit 854618 LM34 for 125F Shutdown LM35 for 125C Shutdown 21 www.national.com 854623 LP2950/LP2951 Schematic Diagram www.national.com 22 LP2950/LP2951 Physical Dimensions inches (millimeters) unless otherwise noted Order Number LP2951WG/883 NS Package Number WG10A Metal Can Package (H) NS Package Number H08C 23 www.national.com LP2950/LP2951 Ceramic Dual-In-Line Package (J) NS Package Number J08A Surface Mount Package (M) NS Package Number M08A www.national.com 24 LP2950/LP2951 Molded Dual-In-Line Package (N) NS Package Number N08E Molded TO-92 Package (Z) NS Package Number Z03A 25 www.national.com LP2950/LP2951 Surface Mount Package (MM) NS Package Number MUA08A D-Pak Package NS Package Number TD03B www.national.com 26 LP2950/LP2951 LLP Package NS Package Number SDC08A 27 www.national.com LP2950/LP2951 Series of Adjustable Micropower 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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