MICREL LP2950/2951 100mA Low-Dropout Voltage Regulator handbook
Contents
1. 250 Z D 225 E ES 200 5 9 a R 50kQ i Z Z 175 1 G u 4 z a o R 50kQ wi 150 2 lt tc o 5 a 125 z o FR 2500 O 100 R 2 o0 a gt L n o 04 f 2 5 75 z 3 a 2 a z 50 Oo EX t o 25 0 01 0 0 0 1 1 10 150 0 1 2 3 4 5 6 012345678910 LOAD CURRENT mA INPUT VOLTAGE VOLTS INPUT VOLTAGE VOLTS Output Voltage vs Temperature of 3 Input Current Representative Units Ground Current 160 5 06 320 150 T bes R BO S 5 04 e 280 e y ET z 100 g ave HI 200 S x z g 80 O 50 2 160 a G 120 EK 2 4 98 i 2 a 0 5 0 2 Q 80 Z O 4 96 G Es 40 10 0 4 94 0 0123 45 67 8 9 10 75 50 25 0 25 50 75100125 150 012 3 4 5 6 7 8 INPUT VOLTAGE VOLTS TEMPERATURE C INPUT VOLTAGE VOLTS Quiescent Current Ground Current Ground Current 240 16 T T T 3 t 14 Z 220 E Kb 12 S T Vn 6V 12 SEN I 100 mA E I 100 pA fE oc 3 2 Vin EN E 8 200 o IL 2 100 mA o Z E eg o 6 W z 8 z oO 2 5 a o 4 UI rai o 5 180 5 2 4 0 75 50 25 0 25 50 75 100 125 150 75 50 25 0 25 50 75 100125 150 012 34 56 7 8 TEMPERATURE C TEMPERATURE C INPUT VOLTAGE V Short Circuit Current Drop out Voltage Drop out Voltage 170 600 500 E ee gt 100 mA gt z eo E 400 LLI LLI E 150 Q 400 9 Q 140 5 EN Q 300 9 3 130 C m E 200 E 120 g 100 o E 5 oh Rw S 110 Q 50 IL 100 pA ra I a a o 100 0 0 75 502. VOUT LP2951 1 ERROR NICAD 330kQ ViN SENSE MAIN OUTPUT VOUT LP2951 2 ERROR Regulator with Early Warning and Auxiliary Output EARLY WARNING FLAG ON LOW INPUT VOLTAGE MAIN OUTPUT LATCHES OFF AT LOWER INPUT VOLTAGES BATTERY BACKUP ON AUXILIARY OUTPUT OPERATION REG 1 S Vur IS PROGRAMMED ONE DIODE DROP ABOVE 5 V ITS ERROR FLAG BECOMES ACTIVE WHEN Vp lt 5 7 V WHEN Na DROPS BELOW 5 3 V THE ERROR FLAG OF REG 2 BECOMES ACTIVE AND VIA Q1 LATCHES THE MAIN OUTPUT OFF WHEN V AGAIN EXCEEDS 5 7 V REG 1 IS BACK IN REGULATION AND THE EARLY WARNING SIGNAL RISES UNLATCHING REG 2 VIA D3 February 1999 3 45 LP2950 2951 Micrel 5V 4 20mA 4 7mA k k OUTPUT 1 m VIN 5 ERROR VOUT OUT wv K LP2951 MIC2951 4 2 HIGH FOR bd bd c MIN VOLTAGE 4V Latch Off When Error Flag Occurs Open Circuit Detector for 4mA to 20mA Current Loop Vin SENSE ERROR VOUT LP2951 ga ACID BATTERY i De iis ko 100kQ 6 0V C1 C4 P339 1 Sto 100kQ 6 2V 10ko R3 1 20kQ OPTIONAL LATCH OFF WHEN DROP OUT OCCURS ADJUST R3 FOR C2 SWITCHING WHEN V y IS 6 0V OUTPUTS GO LOW WHEN Vy DROPS BELOW DESIGNATED THRESHOLDS Regulator with State of Charge Indicator 3 46 February 1999 LP2950 2951 Micrel tL ev SEALED LEAD ACID B
3. 195 Note 7 LP2951 4 8 1 Note 7 LP295x 02 0 5 Note 12 LP295x 03 1 Note 12 LP2951 4 8 1 Note 12 RE REL BER Le ea E UE L L m MI lt lt lt lt lt lt lt lt lt LP295x 02 0 5 Low High LP295x 03 Low High LP2951 4 8 1 Low High Co e N lt lt lt lt lt lt j lt lt lt 3 38 February 1999 LP2950 2951 Micrel Parameter Shutdown Input Current Regulator Output Current in Shutdown Note 1 Boldface limits apply at temperature extremes Note 2 Unless otherwise specified all limits guaranteed for T 25 C Vi 6V 100A and C 1uF Additional conditions for the 8 pin versions are Feedback tied to 5V Tap and Output tied to Output Sense Voy7 5V and Veyytpown lt 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 100mV 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 6V input To expr
4. AMPLIFIER SVTAP F kO OR TTL DOWN 60 mV N 60 5 4 D kQ l S TO CMOS i Z ERROR PRROR OR TTL 123 v DETECTION n REF T COMPARATOR bd GROUND LP2950 and LP2951 Block Diagram Pin Numbers Refer to LP2951 1 8 OUTPUT INPUT SENSE 2 7 FEEDBACK OUTPUT INPUT sHUTDOWN 3 S 5V TAP GROUND GROUND 4 5 ERROR TO 92 Plastic Package Bottom View DIP and SO Packages BZ BN and BM See MIC2950 for a part with 1 higher output 150 mA 2 transient protection 60V and 3 reverse input protection to 20V February 1999 3 35 LP2950 2951 Additional features available with the LP2951 also include an error flag output that warns of a low output voltage which is often due to failing batteries on the input This may also be used as a power on reset A logic compatible shutdown input is also available which enables the regulator to be switched on and off This part may also be pin strapped for a 5V output or programmed from 1 24V to 29V with the use of two external resistors The LP2950 is available as either an 02 or 03 version The 02 and 03 versions are guaranteed for junction temperatures Ordering Information Micrel from 40 C to 125 C the 02 version has atighter output and reference voltage specification range over temperature The LP2951 is available as an 02 or 03 version The LP2950 and LP2951 have a tight initial tolerance 0 5 typical a very low output voltage temperature coefficient which allows use as a
5. T lt T ja 5 120 V LP2951 4 8 1 100A lt I lt 100MA Ty lt Timax V Output Voltage LP295x 02 0 595 Note 12 100 ppm C Temperature Coefficient LP295x 03 1 Note 12 150 ppm C LP2951 4 8 195 Note 12 180 ppm C E Line Regulation LP295x 02 0 5 Notes 14 15 3 0 20 LP295x 03 1 Notes 14 15 4 1 4 4 0 0 0 0 0 0 0 0 4 6 0 1 0 20 0 2 0 30 Dropout Voltage Note 5 100A 80 mV 150 mV Note 5 100mA 2 4 Ground Current l 1004A l 100mA Dropout Current Vin 4 5V l 1004A 45 mV 600 mV 150 200 1 mA 1 mA 25 uA 310 uA je E i D Es e B RENI ERR E RCNH EA aE 0 30 IS RE 0 250 5 38 1 18 LP2951 4 8 196 Note 14 100pA lt I lt 100mA NE February 1999 3 37 LP2950 2951 Parameter Current Limit Thermal Regulation Output Noise Reference Voltage Reference Voltage Feedback Bias Current Reference Voltage Feedback Bias Current Temperature Coefficient Output Leakage Current Output Low Voltage Flag Upper Threshold Voltage Lower Threshold Voltage Hysteresis Input Logic Voltage Micrel we o Ga E 220 m Ee es om ww 10Hz to 100kHz C 3 3uF 100 H owes 0 01uF bypass Feedback to Output LP295x 02 0 5 1 220 1 235 1 250 1 200 1 260 LP295x 03 1 1 210 1 235 1 260 1 200 1 270 LP2951 4 8 41 1 210 1 235 1 260 1 200 1 270 LP295x 02 0 5 Note 7 LP295x 03
6. 25 0 25 50 75 100 125 150 75 50 25 0 25 50 75 100125 150 100 yA 1mA 10 mA TEMPERATURE C TEMPERATURE C OUTPUT CURRENT 100 mA Micrel February 1999 LP2950 2951 Micrel LP2951 LP2951 LP2951 s Minimum Operating Voltage m Feedback Bias Current Feedback Pin Current fo gt PIN DRIVEN BY EXTERNAL x lt SOURCE REGULATOR RUN E24 Gi 3 0 F OPEN LOOP 21 a 10 e S E G 50 o 20 5 9 C T 125 C Zz UI tc E 19 E 3 100 d d 10 5 a 18 D amp 150 9 E m Ty 25 C Sy 47 a ae 2 200 u zl 55 C Z 16 30 250 75 50 25 0 25 50 75 100125 150 75 50 25 0 25 50 75 100125 150 2 0 1 5 1 0 0 5
7. low power voltage reference and extremely good load and line regulation 0 05 typical This greatly reduces the error in the overall circuit and is the result of careful design techniques and process control Part Number Voltage Temperature Range LP2950 02BZ 40 C to 125 C 3 Pin TO 92 plastic LP2950 03BZ 40 C to 125 C 3 Pin TO 92 plastic LP2951 02BM 40 C to 125 C 8 Pin SOIC Junction temperatures Absolute Maximum Ratings If Military Aerospace specified devices are required contact your local Micrel representative distributor for availability and specifications Power dissipation Lead Temperature Soldering 5 seconds Storage Temperature Range Internally Limited 260 C 65 C to 150 C Operating Junction Temperature Range Note 8 LP2950 LP2951 Input Supply Voltage Feedback Input Voltage Notes 9 and 10 Shutdown Input Voltage Note 9 Error Comparator Output Voltage Note 9 ESD Rating is to be determined 3 36 40 C to 125 C 0 3V to 30V 1 5V to 30V 0 3V to 30V 0 3V to 30V February 1999 LP2950 2951 Micrel Electrical Characteristics Note 1 T 25 C except as noted 0 20 0 40 LP2951 4 8 1 Notes 14 15 0 20 0 40 Load Regulation LP295x 02 0 5 Note 14 100A lt I lt 100mA LP295x 03 41 Note 14 100uA zl lt 100mA Output Voltage LP295x 02 0 5 V v v v Oat Road SS LP295x 03 1 100A lt 1 lt 100MA
8. 0 05 1 0 TEMPERATURE C TEMPERATURE C FEEDBACK VOLTAGE V LP2951 LP2951 Error Comparator Output Comparator Sink Current wu 100 Line Transient Response _ 8 Soi Pa ell vie O mV Vout 5V PE TA 125 C Eu 50 5 6 T 20 OO mV E E ES D 5I d 4 Z 15 T 25 C 4 go lo HYSTERESIS cc 5 50 C 1pF _ o S j S o met l 21mA S eT T C 8V Vout DV E S a D I y a E o o 05 at ev 9 PULLUP RESISTOR TO Sa 2 SEPARATE 5V SUPPLY 0 0 O ay 0 1 2 3 4 5 0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 200 400 600 800 INPUT VOLTAGE V OUTPUT LOW VOLTAGE V TIME us LP2951 Load Transient Response Load Transient Response Enable Transient ul 250 ul 0 cef a Qs 200 Ss GER m FE 150 HE ao 5 Qu 100 Qu 5E 4 E 2 50 E Z Od ar 0 ET PO Ng 2 10 mA 29 50 39 ONE Vin 8V O 400 C 1 pF 9 Zu C_ 10 UF Vour DN E ke Vout 5V H Eo H ag 100 m 9 se MUTT Bg Ge 100 Or 29 Si 2 7 2 0 1 2 3 4 5 9 0 4 8 12 16 20 100 0 100 200 300 400 500 600 700 TIME ms TIME ms TIME us Output Impedance Ripple Rejection Ripple Rejection 8 10 0 90 2 e ils 100 pa 4 SS oO a 9 2Lh 1mA 3 ae Cw MF W B z Z ji 1mA wna OY o 1 a 100 mA o S r our 5V amp 05 O G o w i 3 a 0 2 Voyr 5V n H 50 Z 0 1 Ci 1 pF i U 4o g 0 05 a a E e c 30 a 2 GE 30 lI 10 mA 10 100 1K 10K 100K 1M 10 10 10 104 10 10 10 10 10 10 10 10 FREQUENCY Hz FREQUENCY Hz FREQUENCY Hz February 1999 3 41 Micrel LP2950 2951 Typical Performance Ch
9. 2V output The out of regulation condition may be due either to low input voltage current limiting or thermal limiting Figure 1 is a timing diagram depicting the ERROR signal and the regulated output voltage as the LP2951 inputis ramped up and down The ERROR signal becomes valid low at about 1 3V input It goes high at about 5V input the input voltage at February 1999 Micrel which Vour 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 approximately 4 75V does not vary with load The error comparator has an open collector output which requires an external pull up resistor Depending on system requirements this resistor may be returned to the 5V output or some other supply voltage In determining a value for this resistor note that while the output is rated to sink 400uA this sink current adds to battery drain in a low battery condition Suggested values range from 100kto 1 MO The resistor is not required if this output is unused Programming the Output Voltage LP2951 The LP2951 may be pin strapped for 5V using its internal voltage divider by tying Pin 1 output to Pin 2 SENSE and Pin 7 FEEDBACK to Pin 6 BV TAP Alternatively it may be programmed for any output voltage between its 1 235V reference and its 30V maximum rating An external pair of r
10. ATTERY SOURCE 400kQ FOR 5 5V Sets disconnect voltage Sets disconnect hysteresis gt MAIN V LP2951 SENSE gt MEMORY V 202 NI CAD BACKUP BATTERY Low Battery Disconnect For values shown Regulator shuts down when V lt 5 5 V and turns on again at 6 0 V Current drain in disconnected mode is 150uA AUX SHUTDOWN VIN Eug 10kQ 5 5 PRE SHUTDOWN FLAG INPUT Lx OFF ON LM34 for 125 F Shutdown LM35 for 125 C Shutdown February 1999 ERROR MIC2951 VOUT EXTERNAL CIRCUIT o PROTECTED FROM OVER TEMPERATURE V GOES OFF WHEN TEMP 125 System Over Temperature Protection Circuit 3 47 LP2950 2951 Micrel Um FEEDBACK d R18 Q15A 20kQ Q15B QM o Y ox E OUT I SENSE RO lt 182 kO Ee ME P28 60 ka o2 023 R15 100 ka ee RIG RI7 309 ua Q29 43 ove 2 k Ret 8o R23 60 ko son ROA 50 ka 3 48 February 1999
11. GE V e Thermal R n 120 Rated Output g SE ermal Response HE id det t 100 0 25 LEADS SOLDERED 9 u 4 TO PC BOARD oO 5 52 2 80 aT cc T 125 C ES pg 5 60 MAX 6 z Ta 25 C E 2 gt 40 z K a D ii E wie 1 25W 3 20 T 85 C OZ o 0 A 0 5 10 15 20 25 30 a 0 10 20 30 40 50 INPUT VOLTAGE V TIME us 3 42 February 1999 LP2950 2951 Applications Information External Capacitors A 1 0uF or greater capacitor is required between the LP2950 LP2951 output and ground to prevent oscillations due to instability Most types of tantalum or aluminum electrolytics will be adequate film types will work but are costly and therefore not recommended Many aluminum electrolytics have electrolytes that freeze at about 30 C so solid tantalum capacitors are recommended for operation below 25 C The important parameters of the capacitor are an effective series resistance of about 5Q or less and a resonant frequency above 500kHz The value of this capacitor may be increased without limit At lower values of output current less output capacitance is required for output stability The capacitor can be reduced to 0 33uF for current below 10mA or 0 1uF for currents below 1mA Using the 8 Pin versions at voltages below 5V runs the error amplifier at lower gains so that more output capacitance is needed For the
12. LLLI LES OG D LP2950 2951 inm General Description Features The LP2950 and LP2951 are micropower voltage regulators e High accuracy 5V guaranteed 100 mA output with very low dropout voltage typically 40mV at light loads Extremely low quiescent current and 380mV at 100mA and very low quiescent current 75uA Low dropout voltage typical The quiescent current of the LP2950 LP2951 e Extremely tight load and line regulation increases only slightly in dropout thus prolonging battery life Very low temperature coefficient This feature among others makes the LP2950 and LP2951 e Use as regulator or reference ideally suited for use in battery powered systems e Needs only 1uF for stability Available in a 3 Pin TO 92 package the LP2950 is pin S E compatible with the older 5V regulators Additional system functions such as programmable output voltage and logic LP2951 Versions Only controlled shutdown are available in the 8 pin DIP and 8 pin SOIC versions of the LP2951 Error flag warns of output dropout e e Logic controlled electronic shutdown Applications e Output programmable from 1 24 to 29V e Automotive Electronics Voltage Reference Avionics Block Diagram and Pin Configurations UNREGULATED DC 5V ee 150mA MAX EE 7 8 1 p 7 7 FEEDBACK INPUT OUTPUT ESAE L p NI 2 SENSE NS 182 3 Perron 330 COS SHUT
13. aracteristics Continued RIPPLE REJECTION dB SHUTDOWN THRESHOLD VOLTAGE V 70 60 50 40 30 20 10 0 8 Ripple Rejection IL 50 pA 100 mA CL 1 uE Ma 6V Vout 5V 10 10 10 105 10 FREQUENCY Hz 10 Shutdown Threshold Voltage 0 6 ean aa a 75 50 25 0 25 50 75100125 150 TEMPERATURE C E Output Noise TTTTTIT T3 i I 100 mA 80 us CL 1uF OL 25 OF C 220 uF ug 2 0 i LC RS 157X033 ur lt x Se 10 o ll 0 5 ByPASs 77 PIN 1 TO 0 0 PIN 7 10 10 104 105 OUTPUT VOLTAGE CHANGE mV o LP2950 Maximum 5 10 FREQUENCY Hz Line Regulation 100 pA T 150 C 1 l 1mA 100 pA 4 15 20 25 INPUT VOLTAGE V 30 LP2951 Divider Resistance rj 400 LLI 2 lt 300 e o d t 200 b Zz a o 100 E N z a 0 75 50 25 0 25 50 75100125 150 TEMPERATURE C LP2950 Maximum Rated Output Current 120 8 PIN MOLDED z Ze 10 T 125 C E MAX Z 80 Vout 5V tr TA 25 C oc E 60 A o 40 LT 50 C a E o d 20 Tr 85 C 0 0 5 10 15 20 25 30 INPUT VOLTA
14. are for a 50mA load pulse at Vi 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 in the specification for thermal regulation Note 15 Line regulation for the LP2951 is tested at 150 C for I 1mA For 1004A 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 February 1999 3 39 LP2950 2951 Typical Performance Characteristics Quiescent Current Dropout Characteristics 3 40 Input Current
15. changes reduce the output noise from 430uV to 100uV rms for a 100kHz 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 CBvPAsS 3 43 LP2950 2951 Micrel SEE APPLICATIONS AN INFORMATION 4 75V di VOUT VREF OUTPUT x 1 ud VOLTAGE R2 VOUT p x OUTPUT oe ERROR NOT NOT 9 VALID WW ka VALID 3 3uF OFF INPUT V VOLTAGE 9 ON pum 1 3V 1 23V NOTE PINS 2 AND 6 ARE LEFT OPEN 4 SEE APPLICATIONS INFORMATION VREF Ro Figure 1 ERROR Output Timing d E Figure 2 Adjustable Regulator Typical Applications V IN VIN C MOS SLEEP GATE 8 INPUT ERROR NR WW V TRE 5 ERROR Vout HU QUT IN OUTPUT av du LP2951 ERROR VoUT SHUTDOWN 3 200ko INPUT SE 1 4 100kQ 3 34F MINIMUM INPUT OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV HIGH INPUT LOWERS Vj TO 2 5V DEPENDING ON LOAD CURRENT CURRENT LIMIT IS TYPICALLY 160mA 8 SES SVa I9 5 Wide Input Voltage Range Current Limiter 5 V Regulator with 2 5 V Sleep Function 3 44 February 1999 Micrel LP2950 2951 2 gt 30V S ieee 1 23 ILLI LOAD Ti V R TV IN ae ee ey Jd Vout LP2950Z VOUT LP2951 SHUTDOWN 3 0 1uF 5 Volt Current Limiter MINIMUM INPUT OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV DEPENDING ON LOAD CURRENT Low Drift Current Source VIN Dy ViN SENSE MEMORY
16. esistors is required as shown in Figure 2 The complete equation for the output voltage is Vour Maer X 1 R R2 lpg R where V is the nominal 1 235 reference voltage and lpg is the feedback pin bias current nominally 20 nA The minimum recommended load current of 1 uA forces an upper limit of 1 2 MQ on the value of R if the regulator must work with no load a condition often found in CMOS in standby I will produce a 2 typical error in Nu which may be eliminated at room temperature by trimming R For better accuracy choosing R 100kQ reduces this error to 0 17 while increasing the resistor program current to 12uA Since the LP2951 typically draws 60 pA at no load with Pin 2 open circuited this is a small price to pay 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 method by which noise can be reduced on the 3 lead LP2950 and is relatively inefficient as increasing the capacitor from 1uF to 220uF only decreases the noise from 430uV to 160uV rms for a 100kHz bandwidth at 5V output Noise can be reduced fourfold by a bypass capacitor across R since it reduces the high frequency gain from 4 to unity Pick i ZO 200 Hz or about 0 01 uF When doing this the output capacitor must be increased to 3 3 uF to maintain stability These
17. ess these thresholds in terms of output voltage change multiply by the error amplifier gain Vor Vage 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 384mV Thresholds remain constant as a percent of Vom as Vout is varied with the dropout warning occurring at typically 5 below nominal 7 5 guaranteed Note 7 Vgge Voyt Viy 1 V 2 3V Vin 30V 100HA lt lj lt 100mA Ty T jux Note 8 The junction to ambient thermal resistance of the TO 92 package is 180 C W with 0 4 leads and 160 C W with 0 25 leads to a PC board The thermal resistance of the 8 pin DIP package is 105 C W junction to ambient when soldered directly to a PC board Junction to ambient thermal resistance for the SOIC M package is 160 C W 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 Vouytpown 2 2V Vin 30 V Mou 0 with Feedback pin tied to 5V Tap 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
18. worst case situation of a 100mA load at 1 23V output Output shorted to Feedback a 3 3uF or greater capacitor should be used The LP2950 will remain stable and in regulation with no load in addition to the internal voltage divider unlike many other voltage regulators This is especially important in CMOS RAM keep alive applications When setting the output voltage ofthe LP2951 version with external resistors a minimum load of 1uA is recommended A 0 1uF capacitor should be placed from the LP2950 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 pin 7 can cause instability This may especially be a problem when using 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 3uF will remedy this Error Detection Comparator Output Alogiclow output will be produced by the comparator 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 235V reference voltage Refer to the block diagram on Page 1 This trip level remains 596 below normal regardless of the programmed output voltage of the LP2951 For example the error flag trip level is typically 4 75V for a 5V output or 11 4V for a 1
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MICREL LP2950/2951 100mA Low Dropout Voltage Regulator handbook