Advanced Monolithic Systems LP2950/LP2951 100mA LOW DROPOUT VOLTAGE REGULATOR RoHS compliant FEATURES APPLICATIONS • 5V, 3.3V, and 3V Versions at 100mA Output Current • High Accuracy Output Voltage • Extremely Low Quiescent Current • Low Dropout Voltage • Extremely Tight Load and Line Regulation • Very Low Temperature Coefficient • Current and Thermal Limiting • Needs Minimum Capacitance (1µF) for Stability • Unregulated DC Positive Transients 60V • Battery Powered Systems • Portable Consumer Equipment • Cordless Telephones • Portable (Notebook) Computers • Portable Instrumentation • Radio Control Systems • Automotive Electronics • Avionics • Low-Power Voltage Reference ADDITIONAL FEATURES (LP2951 ONLY) • 1.24V to 29V Programmable Output • Error Flag Warning of Voltage Output Dropout • Logic Controlled Electronic Shutdown GENERAL DESCRIPTION The LP2950 and LP2951 are micropower voltage regulators ideally suited for use in battery-powered systems. These devices feature very low quiescent current (typ.75µA), and very low dropout voltage (typ.45mV at light loads and 380mV at 100mA) thus prolonging battery life. The quiescent current increases only slightly in dropout. The LP2950/LP2951 has positive transient protection up to 60V and can survive unregulated input transient up to 20V below ground. The LP2950 and LP2951 were designed to include a tight initial tolerance (typ. 0.5%), excellent load and line regulation (typ. 0.05%), and a very low output voltage temperature coefficient, making these devices useful as a low-power voltage reference. The LP2950 is offered in the 3-pin TO-92 package. LP2951 is available in 8-pin plastic SOIC and DIP packages and offers three major additional system features. An error flag output warns of a low output voltage, often due to failing batteries on input. The LP2951 also features the logic-compatible shutdown input which enables the regulator to be switched on and off. The LP2951 device may be pin-strapped for a 5V, 3.3V, or 3V output, or programmed from 1.24V to 29V with an external pair of resistors. ORDERING INFORMATION PIN CONNECTION PACKAGE TYPE TO-92 8 LEAD PDIP 8 LEAD SOIC LP2950ACN-X LP2951ACP-X LP2951ACS-X LP2950CN-X LP2951CP-X LP2951CS-X OPERATING TEMP. RANGE IND. IND 8L SOIC/ 8L PDIP OUTPUT 1 8 INPUT SENSE 2 7 FEEDBACK SHUTDOWN 3 6 VTAP GROUND 4 X = 3.3V, or 3V 5 ERROR Top View TO-92 OUTPUT INPUT GND Bottom View Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage -0.3 to +30V OPERATING RATINGS (Note 1) SHUTDOWN Input Voltage, Error Comparator Output Voltage,(Note 9) FEEDBACK Input Voltage (Note 9) (Note 10) Power Dissipation Junction Temperature Storage Temperature Soldering Temperature (25 sec) Max. Input Supply Voltage Junction Temperature Range (TJ) (Note 8) LP2950AC-XX, LP2950C-XX LP2951AC-XX, LP2951C-XX -1.5 to +30V Internally Limited +150°C -65°C to +150°C 260°C 30V -40°C to +125°C ELECTRICAL CHARACTERISTICS at Vs=Vout+1V, Ta=25°C, unless otherwise noted. Parameter LP2950AC LP2951AC Conditions (Note 2) Min. Typ. LP2950C LP2951C Max. Min. Typ. Units Max. 3 V Versions (Note 16) Output Voltage Output Voltage TJ = 25°C (Note 3) -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µA ≤IL ≤100 mA TJ ≤TJMAX 2.985 3.0 3.015 2.970 3.0 3.030 V 2.970 3.0 3.030 2.955 3.0 3.045 V 2.964 3.0 3.036 2.940 3.0 3.060 V 2.958 3.0 3.042 2.928 3.0 3.072 V 3.284 3.3 3.317 3.267 3.3 3.333 V 3.267 3.3 3.333 3.251 3.3 3.350 V 3.260 3.3 3.340 3.234 3.3 3.366 V 3.254 3.3 3.346 3.221 3.3 3.379 V 4.975 5.0 5.025 4.95 5.0 5.05 V 4.95 5.0 5.050 4.925 5.0 5.075 V 4.94 5.0 5.06 4.90 5.0 5.10 V 4.925 5.0 5.075 4.88 5.0 5.12 V 3.3 V Versions (Note 16) Output Voltage Output Voltage TJ = 25°C (Note 3) -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µA ≤IL ≤100 mA TJ ≤TJMAX 5 V Versions (Note 16) Output Voltage Output Voltage TJ = 25°C (Note 3) -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µA ≤IL ≤100 mA TJ ≤TJMAX All Voltage Options Output Voltage Temperature Coefficient 20 ppm/°C 50 Line Regulation (Note 14) (Note 12) (Note 4) 6V ≤Vin ≤30V (Note 15) 0.03 0.1 0.04 0.2 % Load Regulation (Note 14) 100 µA ≤IL ≤ 100 mA 0.04 0.1 0.1 0.2 % Dropout Voltage (Note 5) IL = 100µ A IL = 100 mA 50 80 50 80 mV 380 450 380 450 mV Ground Current IL = 100 µA IL = 100 mA 75 120 75 120 µA 8 12 8 12 mA Current Limit Vout = 0 160 200 160 200 mA Thermal Regulation (Note 13) 0.05 0.2 0.05 0.2 %/W Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 ELECTRICAL CHARACTERISTICS (Note 2) (Continued) PARAMETER LP2950AC LP2951AC CONDITIONS (Note 2) Output Noise, 10Hz to 100KHz Min. Typ. CL = 1µF Reference Voltage Over Temperature (Note 7) Reference Voltage Temperature Coefficient 160 µV rms 100 100 µV rms LP2951AC LP2951C 1.235 1.21 1.27 1.185 1.235 1.26 V V 60 nA 20 50 ppm/°C 0.1 0.1 nA/°C 60 40 ( Note 12 ) V OH = 30V 0.01 1 0.01 1 µA 150 250 150 250 mV Output Low Voltage Vin = 4.5V IOL = 400µA Upper Threshold Voltage (Note 6) Lower Threshold Voltage (Note 6) 75 Hysteresis Shutdown Input (Note 6) 15 Input logic Voltage 1.25 1.285 40 Feedback Pin Bias Current Temperature Coefficient Error Comparator Output Leakage Current Units 160 1.19 Feedback Pin Bias Current Max. µV rms (Bypass = 0.01 µF pins 7 to 1(LP2951)) 1.22 Typ. 430 CL = 13.3 µF Reference Voltage Min. Max. 430 CL = 200 µF 8-Pin Versions only LP2950C LP2951C 40 Low (Regulator ON) High (Regulator OFF) 60 1.3 40 95 60 75 mV 95 15 0.7 2 mV mV 1.3 0.7 2 V V Shutdown Pin Input Current (Note 3) Vs = 2.4V Vs = 30V 30 50 30 50 µA 450 600 450 600 µA Regulator Output Current in Shutdown (Note 3) (Note 11) 3 10 3 10 µA 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 = 100 µA and CL = 1 µF for 5V versions and 2.2µF 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 = 25°C 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 95 mV x 5V/1.235 = 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), 2.3 ≤Vin≤30V, 100µA≤IL≤ 100 mA, TJ ≤ TJMAX. Note 8: The junction-to-ambient thermal resistance are as follows:180°C/W and 160°C/W for the TO-92 (N) package with 0.40 inch and 0.25 inch leads to the printed circuit board (PCB) respectively, 105°C/W for the molded plastic DIP (P) and 160°C/W for the molded plastic SO-8 (S). The above thermal resistances for the N, S and P packages apply when the package is soldered directly to the PCB. 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 5VTAP. Note 12: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range. Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 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 =10 ms. 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 150°C for IL = 1 mA. For IL = 100 µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%. See typical performance characteristics for line regulation versus temperature and load current. Note 16: 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 of the part number. BLOCK DIAGRAM AND TYPICAL APPLICATIONS LP2950-XX LP2951-XX 7 FEEDBACK + + INPUT VOUT IL≤ 100mA OUTPUT ERROR AMPLIFIER + SEE APPLICATION HINTS 1.23V REFERENCE 1 OUTPUT 2 FROM CMOS OR TTL - 3 SHUTDOWN + 50mV + 8 INPUT SENSE + + - VOUT IL≤ 100mA UNREGULATED DC UNREGULATED DC + ERROR AMPLIFIER 6 VTAP SEE APPLICATION HINTS 330kΩ 5 + 1.23V REFERENCE + TO CMOS OR TTL ERROR 4 GROUND GROUND ERROR DETECTION COMPARATOR Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current Dropout Characteristics 10 Input Current 6 250 225 1 0.1 0.01 0.1 1 10 LOAD CURRENT (mA) 4 RL= 50Ω 2 1 1 125 100 2 3 4 5 6 7 8 INPUT VOLTAGE (V) 75 50 0 9 10 1 QUIESCENT CURRENT ( µA) 5.02 5.0 4.98 0.2% 4.96 IL= 1 mA 100 80 IL= 0 60 40 20 4.94 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 0 0 1 80 70 60 50 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) Advanced Monolithic Systems, Inc. 2 3 4 5 6 INPUT VOLTAGE (V) 7 8 Quiescent Current 8 5V OUTPUT 5V OUTPUT 9 VIN= 6V IL= 100mA 8 7 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) www.advanced-monolithic.com QUIESCENT CURRENT ( µA) 90 QUIESCENT CURRENT (mA) VIN= 6V 100 9 10 120 Quiescent Current IL= 100µA 2 3 4 5 6 7 8 INPUT VOLTAGE (V) 5V OUTPUT 140 10 5V OUTPUT RL= ∞ Quiescent Current 5.04 Quiescent Current QUIESCENT CURRENT ( µA) 6 5V OUTPUT RL= 50Ω 0 150 160 5V OUTPUT 120 110 2 3 4 5 INPUT VOLTAGE (V) RL= 50 kΩ 175 25 0 5.06 OUTPUT VOLTAGE (V) INPUT CURRENT (mA) 1 0 5V OUTPUT 200 Temperature Drift of 3 Representative Units Input Current 120 110 100 90 80 70 60 50 40 30 20 10 0 RL= 50 kΩ 3 0 100 INPUT CURRENT ( µA) OUTPUT VOLTAGE (V) GROUND CURRENT (mA) 5V OUTPUT 5 7 6 5 IL= 100mA 4 3 2 1 0 0 Phone (925) 443-0722 1 2 3 4 5 6 INPUT VOLTAGE (V) Fax (925) 443-0723 7 8 LP2950/LP2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Short Circuit Current 150 140 130 120 110 500 400 IL= 100mA 300 ~ ~ 100 50 IL= 100µA 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) LP2951 Minimum Operating Voltage 1.7 TJ = 25°C 100 0 -10 -20 1mA 10mA OUTPUT CURRENT 100mA LP2951 Feedback Pin Current FEEDBACK CURRENT (µA) 1.8 200 50 10 1.9 300 LP2951 Feedback Bias Current 2.1 2.0 400 0 100µA 20 2.2 BIAS CURRENT (nA) PIN 7 DRVEN BY EXTERNAL SOURCE (REGULATOR RUN OPEN LOOP) 0 -50 TA = 125°C -100 -150 TA = 25°C -200 TA = -55°C -250 -2.0 -30 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 1.6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) LP2951 Error Comparator Output LP2951 Comparator Sink Current 9 2.5 7 50k RESISTOR TO EXTERNAL 5V SUPPLY 6 5 4 HYSTERESIS 3 50k RESISTOR TO VOUT 2 1 0 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 Advanced Monolithic Systems, Inc. SINK CURRENT (mA) VOUT= 5V 8 TA = 125°C 2.0 1.5 TA = 25°C 1.0 TA = -55°C 0.5 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 OUTPUT LOW VOLTAGE (V) www.advanced-monolithic.com INPUT OUTPUT VOLTAGE VOLTAGE CHANGE MINIMUM OPERATING VOLTAGE (V) 500 DROPOUT VOLTAGE (mV) 160 DROPOUT VOLTAGE (mV) SHORT CIRCUIT CURRENT ( mA) 600 100 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) ERROR OUTPUT (V) Dropout Voltage Dropout Voltage 170 0 0.5 -1.5 -1.0 -0.5 FEEDBACK VOLTAGE (V) 1.0 Line Transient Response 100 mV 50 mV 0 -50 mV CL= 1µF IL= 1mA ~ ~ VOUT= 5V 8V 6V 4V 0 Phone (925) 443-0722 200 400 TIME (µs) 600 Fax (925) 443-0723 800 LP2950/LP2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 100 mA 100 µA 1 2 3 TIME (ms) 4 5 0 RIPPLE REJECTION (dB) IO= 100mA IO= 1 mA 0.5 0.2 VOUT = 5V CL= 1 µF 0.05 0.02 0.01 16 OUTPUT VOLTAGE (V) 20 5 4 3 2 1 0 2 80 80 70 IL= 0 50 IL= 100µA CL= 1 µF VIN= 6V 30 ~ ~ Ripple Rejection 90 40 CL= 10 µF IL= 10 mA VIN = 8V VOUT = 5V 0 -2 -100 0 100 200 300 400 500 600 700 TIME (µs) 90 60 CL= 1 µF VOUT = 5V 70 CL= 1 µF VIN= 6V VOUT = 5V IL= 1mA 60 50 40 30 IL= 10mA 10 100 1K 10K 100K FREQUENCY (Hz) 20 10 1 1M Ripple Rejection 60 IL= 100mA CL= 1µF VIN= 6V 30 VOUT= 5V 20 10 10 1 10 6 10 2 10 5 10 3 10 4 FREQUENCY (Hz) Advanced Monolithic Systems, Inc. 10 6 IL= 100mA CL= 1 µF 2.5 2.0 1.5 CL= 3.3 µF CL= 220 µF 1.0 0.0 10 5 10 3 10 4 FREQUENCY (Hz) 10 6 LP2951 Divider Resistance 3.0 0.5 10 2 400 5V OUTPUT IL= 50mA 50 40 10 5 10 3 10 4 FREQUENCY (Hz) 3.5 VOLTAGE NOISE SPECTRAL DENSITY(mV/√Hz) 70 10 2 20 10 1 LP2951 Output Noise 80 RIPPLE REJECTION (dB) 8 12 TIME (ms) PIN 2 TO PIN 4 RESISTANCE (k Ω) OUPUT IMPEDANCE (Ω) 2 0.1 4 7 6 Ripple Rejection IO= 100µA 1 VOUT = 5V ~ ~ Output Impedance 10 5 CL= 10 µF RIPPLE REJECTION (dB) 0 100 mA 100 µA LP2951 Enable Transient SHUTDOWN PIN VOLTAGE (V) CL= 1 µF VOUT = 5V ~ ~ OUTPUT VOLTAGE CHANGE (mV) Load Transient Response 80 60 40 20 0 -20 -40 -60 LOAD CURRENT LOAD CURRENT OUTPUT VOLTAGE CHANGE (mV) Load Transient Response 250 200 150 100 50 0 -50 -100 0.01 µF BYPASS PIN 1 TO PIN 7 10 2 10 3 10 4 FREQUENCY (Hz) www.advanced-monolithic.com 10 5 300 200 100 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 1.6 REGULATOR OFF 1.2 1.0 REGULATOR ON 0.8 0.6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 30 25 20 15 10 5 0 120 OUTPUT CURRENT ( mA) 1.8 1.4 LP2951 Maximum Rated Output Current Line Regulation OUTPUT VOLTAGE CHANGE (V) SHUTDOWN TRESHOLD VOLTAGE (V) Shutdown Treshold Voltage IL= 100µA TJ = 150° C IL= 1mA ~ ~ 10 5 0 -5 -10 IL= 100µA TJ = 125° C 15 20 25 10 INPUT VOLTAGE (V) TJMAX= 125° C 60 TA= 25° C 40 TA= 85° C 0 0 10 5 15 20 INPUT VOLTAGE (V) Advanced Monolithic Systems, Inc. 25 30 POWER OUTPUT VOLTAGE DISSIPATION (W) CHANGE (mV) OUTPUT CURRENT ( mA) TO-92 PACKAGE .25"LEADS SOLDERED TO PC BOARD 20 TJMAX= 125° C VOUT = 5V 80 TA= 25° C 60 TA= 50° C 40 20 TA= 85° C 30 10 5 15 20 INPUT VOLTAGE (V) 0 Thermal Response 120 80 100 0 5 LP2950 Maximum Rated Output Current 100 8 PIN MOLDED DIP SOLDERED TO PC BOARD www.advanced-monolithic.com 5 4 2 0 -2 1 ~ ~ 1.25W 0 -1 0 10 20 30 TIME (µs) Phone (925) 443-0722 40 50 Fax (925) 443-0723 25 30 LP2950/LP2951 APPLICATION HINTS External Capacitors A 1.0 µF or greater capacitor is required between output and ground for stability at output voltages of 5V or more. At lower output voltages, more capacitance is required (2.2µ or more is recommended for 3V and 3.3V versions). Without this capacitor the part will oscillate. Most types of tantalum or aluminum electrolytic works fine here; even film types work but are not recommended for reasons of cost. Many aluminum types have electrolytes that freeze at about -30°C, so solid tantalums are recommended for operation below -25°C. The important parameters of the capacitor are an ESR of about 5 Ω or less and resonant frequency above 500 kHz parameters in the value of the capacitor. 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 0.33 µF for currents below 10 mA or 0.1 µF 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 3.3µF (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 version with external resistors, a minimum load of 1µA is recommended. A 1µF tantalum or aluminum electrolytic capacitor should be placed from the LP2950/LP2951 input to the 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. Stray capacitance to the LP2951 Feedback terminal can cause instability. This may especially be a problem when using a higher value of external resistors to set the output voltage. Adding a 100 pF capacitor between Output and Feedback and increasing the output capacitor to at least 3.3 µF will fix this problem. 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 60 mV divided by the 1.235 reference voltage. (Refer to 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 1 gives a timing diagram depicting the ERROR signal and the regulator 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 = 4.75 ). 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 pullup 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 the output is rated to sink 400µA, this sink current adds to battery drain in a low battery condition. Suggested values range from 100K to 1MΩ. The resistor is not required if this output is unused. 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 2, an external pair of resistors is required. The complete equation for the output voltage is: Vout = VREF × (1 + R1/ R2)+ IFBR1 where VREF is the nominal 1.235 reference voltage and IFB is the feedback pin bias current, nominally -20 nA. The minimum recommended load current of 1 µA forces an upper limit of 1.2 MΩ on value of R2, if the regulator must work with no load (a condition often found in CMOS in standby) IFB will produce a 2% typical error in VOUT which may be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100k reduces this error to 0.17% while increasing the resistor program current by 12 µA. Since the LP2951 typically draws 60 µA at no load with Pin 2 open-circuited, this is a small price to pay. Reducing Output Noise In reference applications it may be an 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 that noise can be reduced on the 3 lead LP2950 but is relatively inefficient, as increasing the capacitor from 1 µF to 220 µF only decreases the noise from 430 µV to 160 µV rms for a 100 kHz bandwidth at 5V output. Noise could also be reduced fourfold by a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick CBYPASS ≅ 1 / 2πR1 × 200 Hz or about 0.01 µF. When doing this, the output capacitor must be increased to 3.3 µF to maintain stability. These changes reduce the output noise from 430 µV to 100 µV 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. LP2950/LP2951 Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 APPLICATION HINTS (Continued) +VIN OUTPUT VOLTAGE 4.75V 8 100k VOUT 1.2 30V +VIN ERROR OUPUT ERROR* **SHUTDOWN INPUT 5V INPUT VOLTAGE 5 ERROR* 3 VOUT LP2951 SD R1 GND 4 1.3V 1 FB 7 3.3µF 1.23V VREF FIGURE 1. ERROR Output Timing * + .01 µF R2 FIGURE 2. Adjustable Regulator *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 2), rather than an external 5V source, will keep the error flag voltage under 1.2V (typ.) in this condition. The user may wish to drive down the error flag voltage using equal value resistors (10 kΩ suggested), to ensure a low-level logic signal during any fault condition, while still allowing a valid high logic level during normal operation. *See Application Hints. Vout = VREF × (1 + R1/ R2) **Drive with TTL- high to shut down. Ground or leave if shutdown feature is not used. Note: Pins 2 and 6 are left open. TYPICAL APPLICATIONS 300 mA Regulator with 0.75 Dropout Wide Input Voltage Range Current Limiter UNREGULATED INPUT +VIN 8 IN OUT 1 VTAP FB 7 SENSE GND 4 2N5432 (2) 8 27kΩ LP2951 6 330Ω +VIN ERROR OUPUT 5V OUTPUT 2 4.7µF 5 ERROR VOUT 1 *VOUT ≈ VΙΝ LP2951 LOAD 50mA TO 300mA SHUTDOWN 3 SD INPUT GND 4 FB 7 *Minimum Input-Output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 160 mA LP2950/LP2951 Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 TYPICAL APPLICATIONS (Continued) Low Drift Current Source 30V +V = 2 IL 5Volt Current Limiter LOAD 5V BUS 8 +VIN VIN VOUT 1 *VOUT ≈ 5V LP2950 -5.0 VOUT LP2951 SHUTDOWN 3 SD INPUT 0.1µF GND FB 4 7 R 1% 1µF GND 1µF + *Minimum Input-Output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 160 mA 5V Regulator with 2.5V Sleep Function Open Circuit Detector for 4 to 20mA Current Loop +VIN +5V C - MOS GATE *SLEEP INPUT 4.7kΩ 4 20mA *OUTPUT 1 8 47kΩ 470kΩ +VIN 8 VOUT +VIN ERROR OUPUT 5 ERROR +VOUT VOUT 1 GND FB 4 7 4 7 1% + 3.3µF 2N3906 100kΩ 1% 100kΩ Advanced Monolithic Systems, Inc. 2 FB 200kΩ 100pF 1 LP2951 1N4001 LP2951 SHUTDOWN 3 SD INPUT 5 www.advanced-monolithic.com 0.1µF GND 4 1N457 360 MIN. VOLTAGE ≈ 4V Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 TYPICAL APPLICATIONS (Continued) 2 Ampere Low Dropout Regulator CURRENT LIMIT SECTION Regulator with Early Warning and Auxiliary Output +VIN +VIN = VOUT +.5V 0.05 680 D1 8 +VIN 6 470 7 4.7MΩ VOUT 7 FB GND VOUT 4 1 ERROR FLAG 5 LP2951 220 1µF 3.6V NICAD 4 27 kΩ ERROR SD 20 + GND +VIN 3 5V MEMORY SUPPLY D2 1 LP2951 #1 5 ERROR FB +VOUT @ 2A 10kΩ 8 SENSE VTAP MJE2955 2N3906 2 + R1 + 4.7 TANT. 100µF EARLY WARNING D3 2.7MΩ D4 1% R2 Q1 20kΩ 8 +VIN 6 .033 2 SENSE VTAP 7 FB 3 SD RESET 330 kΩ MAIN 5V OUTPUT VOUT LP2951 #2 5 ERROR + µP VDD 1µF GND 4 VOUT = 1.23V(1+R1/R2) For 5V VOUT, use internal resistors. Wire pin 6 to 7 and pin 2 to +VOUTBuss. • 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. It’s 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. 1A Regulator with 1.2V Dropout Latch Off When Error Flag Occurs +VIN UNREGULATED INPUT 0.01µF 10kΩ 1µF SUPERTEX VP12C 470kΩ 8 IN 6 VTAP SENSE 1ΜΩ OUTPUT 5V ± 1% @ 0 TO 1A 2 + LP2951 7 GND 4 470kΩ LP2951 3 SD 0.002µF RESET VOUT +VIN 1 VOUT ERROR R1 220µF OUT 1 FB 8 5 FB GND 4 7 + 1µF R2 2kΩ IQ ≅ 400µA Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted. 3 LEAD TO-92 PLASTIC PACKAGE (N) 0.180±0.005 (4.572±0.127) 0.060±0.005 (1.524±0.127) DIA 0.060±0.010 (1.524±0.254) 0.90 (2.286) NOM 0.180±0.005 (4.572±0.127) 0.140±0.010 (3.556±0.127) 5° NOM 0.500 (12.70) MIN 0.050 (1.270) MAX UNCONTROLLED LEAD DIMENSIONS 0.015±0.002 (0.381±0.051) 0.016±0.003 (0.406±0.076) 0.050±0.005 (1.270±0.127) 10° NOM N (TO-92 ) AMS DRW# 042391 8 LEAD SOIC PLASTIC PACKAGE (S) 0.189-0.197* (4.801-5.004) 8 7 6 5 0.228-0.244 (5.791-6.197) 0.150-0.157** (3.810-3.988) 1 2 3 4 0.010-0.020 x 45° (0.254-0.508) 0.053-0.069 (1.346-1.752) 0.004-0.010 (0.101-0.254) 0.014-0.019 (0.355-0.483) 0.008-0.010 (0.203-0.254) 0.050 (1.270) TYP 0°-8° TYP 0.016-0.050 (0.406-1.270) S (SO-8 ) AMS DRW# 042293 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 LP2950/LP2951 PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted (Continued). 8 LEAD PLASTIC DIP PACKAGE (P) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255±0.015* (6.477±0.381) 0.045-0.065 (1.143-1.651) 0.300-0.325 (7.620-8.255) 0.130±0.005 (3.302±0.127) 0.065 (1.651) TYP 0.005 (0.127) MIN 0.100±0.010 (2.540±0.254) 0.125 (3.175) MIN 0.009-0.015 (0.229-0.381) 0.015 (0.380) MIN 0.018±0.003 (0.457±0.076) 0.325 +0.025 -0.015 (8.255 +0.635 ) -0.381 P (8L PDIP ) AMS DRW# 042294 *DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS. MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.010" (0.254mm) Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723