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LP2951JAN Series of Adjustable Micropower Voltage Regulators Literature Number: SNVS408
November 30, 2010 Series of Adjustable Micropower Voltage Regulators General Description The LP2951 is a micropower voltage regulator with very low quiescent current (75 μA typ.) and very low dropout voltage (typ. 40mV at light loads and 380mV at 100mA). It is ideally suited for use in battery-powered systems. Furthermore, the quiescent current increases only slightly in dropout, prolong- ing battery life. An additional 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 re- sistors. Careful design of the 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
■ 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 (10mΩ to 6Ω) ■ Error flag warns of output dropout ■ Logic-controlled electronic shutdown ■ Output programmable from 1.24 to 29V
Ordering Information
NS Part Number SMD Part Number NS Package Number Package Description JL2951BPA 5962–3870501BPA J08A 8LD Ceramic DIP Connection Diagrams Dual-In-Line Packages (J) 20168126 Top View © 2010 National Semiconductor Corporation 201681 www.national.com LP2951JAN Series of Adjustable Micropower Voltage Regulators
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Absolute Maximum Ratings (Note 1) Input Supply Voltage −0.3 to +30V Shutdown Input Voltage (Note 3) −0.3 to +30V Error Comparator Output Voltage (Note 3) −0.3 to +30V Feedback Input Voltage (Note 3), (Note 4) −1.5 to +30V Power Dissipation (Note 2) Ceramic DIP 1.0 W @ 25°C Junction Temperature (TJ) +160°C Ambient Storage Temperature Range −65°C ≤ TA ≤ +150°C Ambient Operating Temperature Range −55°C ≤ TA ≤ +125°C Lead Temperature (Soldering 10 Seconds) 260°C Thermal Resistance θJA Ceramic DIP (Still Air @ 0.5W) 131°C/W Ceramic DIP (500LF/Min Air flow @ 0.5W) 75°C/W θJC Ceramic DIP 21°C/W ESD Rating ( Note 5) 500V 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
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The following conditions apply, unless otherwise specified. V IN = 6V, IL = −100µA, CL = 3.3µF, VO = 5V (Nominal), VSD = 0.6V Symbol Parameter Conditions Notes Min Max Units Sub- groups VO Output Voltage 4.975 5.025 V 1 4.94 5.06 V 2, 3 VO Line Line Regulation 6V ≤ VIN ≤ 30V, IL = -1mA -5.0 5.0 mV 1 -25 25 mV 2, 3 VO Load Load Regulation -100µA ≤ IL ≤ -100mA, -5.0 5.0 mV 1 -25 25 mV 2, 3 VD Dropout Voltage IL = -100mA 450 mV 1 600 mV 2, 3 80 mV 1 150 mV 2, 3 IG Ground Current IL = -100mA, 12 mA 1 14 mA 2, 3 120 µA 1 140 µA 2, 3 VO = 15V, VIN = 30V 120 µA 1 140 µA 2, 3 VIN = 30V, VO = 15V 15 mA 1 20 mA 2, 3 IG Diff Ground Current Change 6V ≤ VIN ≤ 30V, -30 30 µA 1 -50 50 µA 2, 3 IGDO Dropout Ground Current VIN = 4.5V, 170 µA 1 200 µA 2, 3 VTh L Error Comparator Lower Threshold Voltage 0.0 0.8 mV 1, 2, 3 VTh U Error Comparator Upper Threshold Voltage 2.0 30 mV 1, 2, 3 θR Thermal Regulation VIN = 30V, IL = -50mA, 2mS ≤ T ≤ 10mS -12.5 12.5 mV 1 ISC Current Limit VO = 0V, 200 mA 1 220 mA 2, 3 IGSC Ground Current At Current Limit VO = 0V, 20 mA 1 25 mA 2, 3 VRef Reference Voltage 1.22 1.25 V 1 1.20 1.26 V 2, 3 VR Line Reference Voltage Line Regulation 2.3V ≤ VIN ≤ 30V -1.9 1.9 mV 1 -10 10 mV 2, 3 VR Load Reference Voltage Output Regulation 1.2V ≤ VO ≤ 29V, VIN = 30V -1.2 1.2 mV 1 -5.0 5.0 mV 2, 3 IFB Feedback Pin Bias Current 40 nA 1 60 nA 2, 3 IOH Error Comparator Output Leakage Current VO = 30V 1.0 µA 1 2.0 µA 2, 3 VOL Error Comparator Output Low Voltage VIN = 4.5V, VSD = 2V 250 mV 1 400 mV 2, 3 5 www.national.com LP2951JAN
Symbol Parameter Conditions Notes Min Max Units Sub- groups ISD Shutdown Pin Input Current VSD = 2.4V 50 µA 1 100 µA 2, 3 VSD = 30V 600 µA 1 750 µA 2, 3 VSDL Shutdown Input Logic Voltage Low (Note 6) 0.6 V 1, 2, 3 VSDH Shutdown Input Logic Voltage High (Note 6) 2.0 V 1, 2, 3 ILKG Regular Output Bias Current In Shutdown VSD = 2V, VIN = 30V, IL = 0mA -10 10 µA 1 -20 20 µA 2, 3 AC Parameters The following conditions apply, unless otherwise specified. V IN = 6V, CL = 3.3µF, VSD = 0.6V Symbol Parameter Conditions Notes Min Max Units Sub- groups RR Ripple Rejection ƒ = 120Hz, VIN = 0.1VRMS 50 dB 4 VNoise Output Noise CL = 1µF 600 µVRMS 7 CL = 3.3µF 250 µVRMS 7 Note 1: Absolute Maximum 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 the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions. Note 2: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature), θJA (package junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PDmax = (TJmax - TA)/ θJA or the number given in the Absolute Maximum Ratings, whichever is lower. Note 3: May exceed input supply voltage. Note 4: 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 5: Human body model, 1.5 kΩ in series with 100 pF. Note 6: Parameter tested go-no-go only. www.national.com 6 LP2951JAN
Typical Performance Characteristics Quiescent Current 20168127 Dropout Characteristics 20168128 Input Current 20168129 Input Current 20168130 Output Voltage vs. Temperature of 3 Representative Units 20168131 Quiescent Current 20168132 7 www.national.com LP2951JAN
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Shutdown Threshold Voltage 20168154 Line Regulation 20168155 Maximum Rated Output Current 20168156 11 www.national.com LP2951JAN
Output Capacitor ESR Range 20168163 Application Hints EXTERNAL CAPACITORS A 1.0μF (or greater) capacitor is required between the output and ground for stability at output voltages of 5V or more. At lower output voltages, more capacitance is required (2.2μF or more is recommended for 3V and 3.3V versions). Without this capacitor the part will oscillate. Most types of tantalum or alu- minum electrolytics work fine here; even film types work but are not recommended for reasons of cost. Many aluminum electrolytics 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 5Ω or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit. Ceramic capacitors whose value is greater than 1000pF should not be connected directly from the LP2951 output to ground. Ceramic capacitors typically have ESR values in the range of 5 to 10m Ω, a value below the lower limit for stable operation (see curve Output Capacitor ESR Range). The reason for the lower ESR limit is that the loop compen- sation of the part relies on the ESR of the output capacitor to provide the zero that gives added phase lead. The ESR of ceramic capacitors is so low that this phase lead does not occur, significantly reducing phase margin. A ceramic output capacitor can be used if a series resistance is added (recom- mended value of resistance about 0.1Ω to 2Ω). At lower values of output current, less output capacitance is required for stability. The capacitor can be reduced to 0.33μF for currents below 10mA or 0.1μF for currents below 1mA. Using the adjustable versions at voltages below 5V runs the error amplifier at lower gains so that more output capaci- tance 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. When setting the output voltage of the LP2951 with external resistors, a minimum load of 1μA is recommended. A 1μF tantalum, ceramic or aluminum electrolytic capacitor should be placed from the LP2951 input 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. Stray capacitance to the LP2951 Feedback terminal can cause instability. This may especially be a problem when us- ing high value external resistors to set the output voltage. Adding a 100pF 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 approxi- mately 5%. This figure is the comparator's built-in offset of about 60mV 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 out- put. The out of regulation condition may be due either to low input voltage, current limiting, or thermal limiting. Figure 1 below gives a timing diagram depicting the ER- ROR 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 V OUT = 4.75V). Since the LP2951's dropout voltage is load-dependent (see curve in typical performance characteristics), the input volt- age 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 re- quires an external pullup resistor. This resistor may be re- turned to the output or some other supply voltage depending on system requirements. In determining a value for this re- sistor, note that while the output is rated to sink 400 μA, this sink current adds to battery drain in a low battery condition. Suggested values range from 100k to 1 M Ω. The resistor is not required if this output is unused. 20168120 www.national.com 12 LP2951JAN
1A Regulator with 1.2V Dropout 20168122 300mA Regulator with 0.75V Dropout 20168121 Wide Input Voltage Range Current Limiter 20168109 *Minimum input-output voltage ranges from 40mV to 400mV, depending on load current. Current limit is typically 160mA. www.national.com 14 LP2951JAN
Regulator with Early Warning and Auxiliary Output 20168111 ■ Early warning flag on low input voltage ■ Main output latches off at lower input voltages ■ Battery backup on auxiliary output 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. 15 www.national.com LP2951JAN
Latch Off When Error Flag Occurs 20168112
2 Ampere Low Dropout Regulator
For 5Vout, use internal resistors. Wire pin 6 to 7, & wire pin 2 to +Vout Bus. www.national.com 16 LP2951JAN
5V Regulator with 2.5V Sleep Function 20168114 *High input lowers Vout to 2.5V Open Circuit Detector for 4 → 20mA Current Loop 20168115 17 www.national.com LP2951JAN
Regulator with State-of-Charge Indicator 20168116 *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. Low Battery Disconnect 20168117 For values shown, Regulator shuts down when Vin < 5.5V and turns on again at 6.0V. Current drain in disconnected mode is ≈ 150μA. *Sets disconnect Voltage **Sets disconnect Hysteresis www.national.com 18 LP2951JAN
System Overtemperature Protection Circuit 20168118 LM34 for 125°F Shutdown LM35 for 125°C Shutdown 19 www.national.com LP2951JAN
Revision History
Released Revision Section Changes 11/30/2010 A New Release, Corporate format 1 MDS data sheet converted into one Corp. data sheet format. MJLP2951-X Rev 1B1 will be archived. www.national.com 20 LP2951JAN
Physical Dimensions inches (millimeters) unless otherwise noted Ceramic Dual-In-Line Package (J) 21 www.national.com LP2951JAN
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