SPX2945 400mA Low Dropout Voltage Regulator with Shutdown FEATURES 8 +VIN ■ Output 3.3V, 5.0V at 400mA Output 1.2V to 20V 1 +VIN VOUT + 100K ■ Very Low Quiescent Current, 100µA SPX2945 ■ Low Dropout Voltage, 420mV at 400mA SHUTDOWN INPUT ■ Extremely Tight Load and Line Regulation 3 SD GND OFF ■ Current & Thermal Limiting 7 0.01µF 10µF ERROR 5 VREF 4 ON ■ Very Low Temperature Coefficient FB ______ ERROR R1 OUTPUT R2 Adjustable Regulator ■ Error Flag Warns Of Output Dropout 5V VIN ■ Logic-Controlled Electronic Shutdown OUT IN SPX2945 ■ Output Programmable From 1.24V to 20V (for SO-8) + + 2.2 µF GND 0.1 µF 5V Regulator Circuit Now Available in Lead Free Packaging DESCRIPTION The SPX2945 is a low power voltage regulator. This device is an excellent choice for use in battery-powered applications such as cordless telephones, radio control systems, and portable computers. The SPX2945 features very low quiescent current (100µA Typ.) and very low dropout voltage. This includes a tight initial tolerance of 1% max and very low output temperature coefficient, making the SPX2945 useful as a lowpower voltage reference. The error flag output feature is used as power-on reset for warning of a low output voltage, due to a falling voltage input of batteries. Another feature is the logic-compatible shutdown input which enables the regulator to be switched on and off. The SPX2945 is offered in 3-pin TO-220 package, SO-8 (same pin out as SPX2951), SOT-223, surface mount 3-Pin TO-252, 3-Pin TO-263 packages and 5-Pin TO-263. The regulator output voltage (of the 8-pin SO-8) may be pin-strapped for a 3.3V and 5.0V or programmed from 1.24V to 20V with an external pair of resistors. Look for SPX2951 for 150mA and SPX2954 for 250mA applications. TO-220-3 (U) TO-263-3 (T) SPX2945 SPX2945 1 1 2 2 3 3 TO-252 (R) TO-263-5 (T5) SPX2945 SPX2945 5 Pin TO-263 1 2 2 8 SPX2945 7 SOT-223 (M3) V IN SPX2945 FEEDBACK GN 3 4 6 5 1 2 3 5V/ 3.3V TAP ERRO VIN GN V OU VOU SD Er VIN VOU GND VOUT VOU SENS SHUTDOWN V IN GN VIN GN 1 3 1 2 3 4 5 V IN GN 8-Pin Surface Mount (S) VOU Note: Tab is Ground Date: 3/14/06 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 1 ©Copyright 2006 Sipex Corporation ABSOLUTE MAXIMUM RATINGS Feedback Input Voltage ................................................ -1.5V to +26V Shutdown Input Voltage ................................................ -0.3V to +26V Error Comparator Output .............................................. -0.3V to +26V ESD Rating ............................................................................ 2kV Min Power Dissipation ........................................................ Internally Limited Lead Temp. (Soldering, 5 Seconds) ............................................. 260°C Storage Temperature Range ........................................ -65°C to +150°C Operating Junction Temperature Range ....................... -40°C to +125°C Input Supply Voltage ......................................................... -20V to +26V ELECTRICAL CHARACTERISTICS Electrical characteristics at VIN = VO+1V, IO = 1mA, COUT = 2.2µF, TA = 25°C, unless otherwise specified. The ♦ denotes the specifications wich apply over full operating tempeture range -40°C to +85°C, unless noted. PARAMETER CONDITIONS (Note 2) MIN TYP MAX UNITS 3.267 3.217 3.3 3.3 3.333 3.382 ♦ 4.950 4.880 5.0 5.0 5.050 5.120 ♦ 100 ♦ 1.5 20 ♦ 6 20 30 ♦ 3.3V Version Output Voltage 1mA ≤ IL ≤ 400mA V 5.0V Version Output Voltage 1mA ≤ IL ≤ 400mA V All Voltage Options Output Voltage Temperature Coefficient (Note1) Line Regulation (Note 3) 6V ≤ VIN ≤ 20V (Note 4) Load Regulation (Note 3) IL=1 to 400mA Dropout Voltage (Note5) Ground Current 20 IL=1mA 60 IL=400mA 360 IL=1mA 100 IL=150mA Current Limit 2 IL=300mA 4 IL=400mA 8 VOUT=0 Thermal Regulation Output Noise, 10Hz to 100kHz, IL=100mA CL=2.2µF CL=33µF PSRR at 100KHz IL=100mA CL=10µF 100 150 450 700 200 300 4 6 8 12 15 25 330 800 0.05 0.2 ppm/°C mV mV mV ♦ ♦ µA ♦ mA ♦ ♦ ♦ ♦ mA %/W 400 260 µVRMS 31 dB Adjustable 8 Pin Version only Reference Voltage Reference Voltage 1.210 Over Temperature 1.235 1.185 20 Reference Voltage Temp. Coefficient 20 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 2 V 1.285 Feedback Pin Bias Current Date: 3/14/06 1.260 40 60 V nA ♦ ppm/°C ©Copyright 2006 Sipex Corporation ELECTRICAL CHARACTERISTICS: Continued Electrical characteristics at VIN = VO+1V, IO = 1mA, COUT = 2.2µF, TA = 25°C, unless otherwise specified. ♦ applies over the full operating temperature range. PARAMETER CONDITIONS (Note 2) MIN Feedback Pin Bieas Current Temperature Coefficient Output Leakage Current Output Low Voltage MAX ♦ 0.1 V0H=20V 0.01 VIN=4.5V I0L=400µA Upper Threshold Voltage (Note 6) Lower Threshold Voltage (Note 6) 150 40 25 (Note 6) Input Logic Voltage Low (Regulator ON) High (Regulator OFF) VS=2.4V 30 VS=26V Regulator Output Current in Shutdown (Note 7) Thermal Resistance Theta Junction-Ambient θJA TO-220-3 TO-263-3 TO-263-5 NSOIC-8 SOT-223 TO-252 1 2 ♦ 250 400 ♦ µA mV mV 95 140 ♦ mV 0.7 2.0 ♦ ♦ 15 1.3 450 10 20 UNITS nA/°C 60 75 Hysteresis Shutdown Pin Input Current TYP mV 50 100 600 750 V µA ♦ ♦ 3 µA ♦ 29.4 31.4 31.2 128.4 62.3 50 ♦ ♦ ♦ ♦ ♦ ♦ °C/W Note 1: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range. Note 2: Unless otherwise specified all limits are guaranteed for Tj = 25°C, VIN = 6V, IL = 1mA and CL = 2.2µF. Additional conditions for the 8-pin versions are feedback tied to 5V/3.3V tap and output tied to output sense (VOUT = 5V) and VSHUTDOWN ≤ 0.8V. Note 3: 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 4: Line regulation for the SPX2945 is tested at 150°C for IL = 1 mA. For TJ = 125°C, line regulation is guaranteed by design. 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 6V input. 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: VSHUTDOWN ≥ 2V, VIN ≤ 26V, VOUT = 0, Feedback pin tied to 5V/3.3V Tap. Date: 3/14/06 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 3 ©Copyright 2006 Sipex Corporation SPX2945 - 5.0V BLOCK DIAGRAM UNREGULATED DC 7 + FEEDBACK 5V at 400mA MAX 1 8 OUTPUT INPUT 2 SENSE + _ FROM CMOS OR TTL 180kΩ . ERROR AMPLIFIER 3 6 5V TAP 330kΩ . SHUTDOWN 60kΩ . + 60 mV + _ ERROR DETECTION COMPARATOR + 1.23V + 5 ______ ERROR 1µF TO CMOS OR TTL 4 REFERENCE GROUND APPLICATION INFORMATION External Capacitors The stability of the SPX2945 requires a 2.2µF or greater capacitor between output and ground. Oscillation could occur without this capacitor. Most types of tantalum or aluminum electrolytic works fine here. For operations of below -25°C solid tantalum is recommended since the many aluminum types have electrolytes that freeze at about -30°C. The ESR of about 5Ω or less and resonant frequency above 500kHz are the most important parameters in the value of the capacitor. The capacitor value can be increased without limit. The SPX2945, unlike other low dropout regulators will remain stable and in regulation with no load in addition to the internal voltage divider. This feature is especially important in applications like CMOS RAM keep-alive. 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, then a 0.1µF tantalum or aluminum electrolytic capacitor should be placed from the input to the ground. Instability can occur if there is stray capacitance to the SPX2945 feedback terminal (pin 7). This could cause more problems when using a higher value of external resistors to set the output voltage. At lower values of output current, less output capacitance is required for stability. For the currents below 10mA the value of the capacitor can be reduced to 0.5µF and 0.15µF for 1mA. More output capacitance needed for the 8-pin version at voltages below 5V since it runs the error amplifier at lower gain. At worst case 4.7µF or greater must be used for the condition of 250mA load at 1.23V output. Date: 3/14/06 This problem can be fixed by adding a 100pF capacitor between output and feedback and increasing the output capacitor to at least 3.3µF. SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 4 ©Copyright 2006 Sipex Corporation Error Detection Comparator Output The Comparator produces a logic low output whenever the SPX2945 output falls out of regulation by more than around 5%. This is around 60mV offset divided by the 1.235 reference voltage. This trip level remains 5% below normal regardless of the programmed output voltage of the regulator. Figure 1 shows the timing diagram depicting the ERROR signal and the regulator output voltage as the SPX2945 input is ramped up and down. The ERROR signal becomes low at around 1.3V input, and goes high around 5V input (input voltage at which VOUT = 4.75). Since the SPX2945’s dropout voltage is load dependent, the input voltage trip point (around 5V) will vary with the load current. The output voltage trip point (approx. 4.75V) does not vary with load. 2% in VOUT, which may be eliminated at room temperature by trimming R1. To improve the accuracy choose the value of R2 = 100k; this reduces the error by 0.17% and increases the resistor program current by 12µA. Since the SPX2945 typically draws 60 µA at no load with Pin 2 open-circuited this is a small price to pay. Reducing Output Noise It may be an advantage to reduce the AC noise present at the output. One way 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 SPX2945 but is relatively inefficient, as increasing the capacitor from 1µF to 220µF only decreases the noise from 430µV to 160µV Vrms for a 100kHz 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 The error comparator has an open-collector output, which requires an external pull-up resistor. Depending on the system requirements the resistor may be returned to 5V output or other supply voltage. In determining the value of this resistor, note that the output is rated to sink 400µA; this value adds to battery drain in a low battery condition. Suggested values range from 100K to 1MΩ. If the output is unused this resistor is not required. CBYPASS ≅1 / 2πR1 x 200 Hz or choose 0.01µF. When doing this, the output capacitor must be increased to 3.3µF to maintain stability. These changes reduce the output noise from 430µV to 100µV Vrms 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. Programming the Output Voltage of SPX2945 The SPX2945 may be pin-strapped for 5V or 3.3V using its internal voltage divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback) to Pin 6 (5V/3.3V Tap). Also, it may be programmed for any output voltage between its 1.235V reference and its 20V maximum rating. As seen in Figure 2, an external pair of resistors is required. Refer to the below equation for the programming of the output voltage:: 4.75V OUTPUT VOLTAGE _______ ERROR* VOUT = VREF x ( 1 + R1/ R2 )+ IFBR1 The VREF is 1.235 and IFB is the feedback bias current, nominally -20nA. The minimum recommended load current of 1 µA forces an upper limit of 1.2 MΩ on value of R2. If no load is presented the IFB produces an error of typically +5.0V INPUT VOLTAGE + +1.3V + * See Application Info. Figure 1. ERROR Output Timing Date: 3/14/06 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 5 ©Copyright 2006 Sipex Corporation PACKAGE: 3 PIN TO-252 E1 E b3 L3 D1 D 1 2 H 3 (L1) L4 L5 BACK VIEW e b2 b θ1 FRONT VIEW SIDE VIEW L Gauge Plane A θ c 3 Pin TO-252 SYMBOL A A1 b b2 b3 c c2 D D1 E E1 e H L L1 L2 L3 L4 L5 ø ø1 Date: 3/14/06 A1 JEDEC TO-252 Dimensions in Inches: Controlling Dimension MIN 0.086 0.025 0.030 0.195 0.018 0.018 0.235 0.205 0.250 0.170 Seating Plane C2 L2 NOM 0.240 .090 BSC 0.370 0.055 0.060 .108 REF .020 BSC 0.035 0.045 0º 0º SIPEX Pkg Signoff Date/Rev: MAX 0.094 0.005 0.035 0.045 0.215 0.024 0.035 0.245 0.265 0.410 0.070 0.050 0.040 0.060 10º 15º Variation AA Dimensions in Millimeters Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 2.18 2.39 0.13 0.64 0.89 0.76 1.14 4.95 5.46 0.46 0.61 0.46 0.89 5.97 6.10 6.22 5.21 6.35 6.73 4.32 2.29 BSC 9.4 10.41 1.4 1.52 1.78 2.74 REF 0.51 BSC 0.89 1.27 1.02 1.14 1.52 0º 10º 0º 15º JL Aug4-05/Rev A SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 6 ©Copyright 2006 Sipex Corporation PACKAGE: 3 PIN TO-220 Thermal Pad E E2 øP Q (H1) D2 D D1 1 L1 FRONT VIEW b2 BACK VIEW L e1 e A b Seating Plane 3 Pin TO-220 A1 H1 SYMBOL SIDE VIEW Chamfer Optional C A2 Date: 3/14/06 E1 JEDEC TO-220 Dimensions in Inches: Controlling Dimension MIN NOM A 0.140 A1 0.020 A2 0.080 b 0.015 0.027 b2 0.045 0.057 c 0.014 D 0.560 D1 0.330 D2 0.480 E 0.380 E1 0.270 E2 e .100 BSC e1 .200 BSC H1 0.230 L 0.500 L1 0.139 ΦP Q 0.100 SIPEX Pkg Signoff Date/Rev: MAX 0.190 0.055 0.115 0.040 0.070 0.024 0.650 0.355 0.507 0.420 0.350 0.030 0.270 0.580 0.250 0.161 0.135 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 7 Variation AB Dimensions in Millimeters: Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 3.56 4.83 0.51 1.27 2.03 2.79 0.25 0.51 1.02 1.14 1.45 1.78 0.25 0.51 14.22 16.51 8.38 8.89 12.19 12.70 9.65 10.67 6.86 8.89 0.76 2.54 BSC 5.08 BSC 5.84 6.86 12.70 14.73 6.35 3.30 4.06 2.54 3.30 JL Aug4-05 / Rev A ©Copyright 2006 Sipex Corporation PACKAGE: 5 PIN TO-263 E Seating Plane A E/2 C2 L1 Chamfer Optional D 1 3 2 4 H 5 c SIDE VIEW See Detail C e b FRONT VIEW Gauge Plane Seating Plane θ L Thermal Pad BACK VIEW L3 DETAIL C 5 Pin TO-263 JEDEC TO-263 (L1) Inches Controlling Dimension D1 E1 Date: 3/14/06 A1 SYMBOL A A1 b c c2 D D1 E E1 e H L L1 L3 O MIN 0.160 0.000 0.020 0.015 0.045 0.330 0.270 0.380 0.245 NOM .067 BSC 0.575 0.070 .010 BSC 0˚ - MAX 0.190 0.010 0.039 0.029 0.065 0.380 0.420 0.625 0.110 0.066 8˚ SIPEX Pkg Signoff Date/Rev: SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 8 Variation BA Millimeters Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 4.06 4.83 0.00 0.25 0.51 0.99 0.38 0.74 11.43 5.84 8.38 9.65 6.86 9.65 10.67 6.22 17.02 BSC 14.61 15.88 1.78 2.79 1.68 2.54 BSC 0˚ 8˚ JL Jan18-06/Rev A ©Copyright 2006 Sipex Corporation PACKAGE: 3 PIN TO-263 E Seating Plane A E/2 C2 L1 SIDE VIEW H D 1 2 Chamfer Optional c 3 e See Detail C b b2 Gauge Plane Seating Plane FRONT VIEW θ L3 A1 L DETAIL C Thermal Pad 3 Pin TO-263 JEDEC TO-263 (L1) Inches Controlling Dimension SYMBOL D1 BACK VIEW E1 Date: 3/14/06 MIN NOM MAX A 0.160 0.190 A1 0.000 0.010 b 0.020 0.039 b2 0.045 0.070 c 0.015 0.029 c2 0.045 0.065 D 0.330 0.380 D1 0.270 E 0.380 0.420 E1 0.245 e .100 BSC H 0.575 0.625 L 0.070 0.110 L1 0.066 L3 .010 BSC O 0˚ 8˚ SIPEX Pkg Signoff Date/Rev: SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 9 Variation AA Millimeters Conversion Factor: 1 Inch = 25.40 mm MIN NOM MAX 4.06 4.83 0.00 0.25 0.51 0.99 1.14 1.78 0.38 0.74 1.14 1.65 8.38 9.65 6.86 9.65 10.67 6.22 2.54 BSC 14.61 15.88 1.78 2.79 1.68 0.25 BSC 0˚ 8˚ JL Aug5-05 / Rev A ©Copyright 2006 Sipex Corporation PACKAGE: 3 PIN SOT-223 D b2 E E1 3 2 1 e e1 TOP VIEW b Gauge Plane A2 A L2 ø L Seating Plane A1 c FRONT VIEW 3 Pin SOT-223 JEDEC TO-261 Inches Conversion Factor: 1 Inch = 25.40 mm Millimeters Controlling Dimension SYMBOL MIN NOM A A1 0.02 A2 1.50 1.60 b 0.66 0.76 b2 2.90 3.00 c 0.23 0.30 D 6.30 6.50 E 6.70 7.00 E1 3.30 3.50 e 2.30 BASIC e1 4.60 BASIC L 0.75 0.25 BASIC L2 ø 0º SIPEX Pkg Signoff Date/Rev: Date: 3/14/06 Variation AA MAX 1.80 0.10 1.70 0.84 3.10 0.35 6.70 7.30 3.70 10º MIN 0.001 0.060 0.026 0.114 0.010 0.248 0.264 0.130 NOM MAX 0.071 0.004 0.063 0.067 0.030 0.033 0.118 0.122 0.012 0.014 0.256 0.264 0.276 0.287 0.138 0.146 0.091 BASIC 0.182 BASIC 0.030 0.010 BASIC 0º 10º JL Aug8-05/Rev A SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 10 ©Copyright 2006 Sipex Corporation PACKAGE: 8 PIN NSOIC D D/2 SIDE VIEW 7 8 5 6 E1/2 A1 Seating Plane E E1 2 1 Pin1 Designator to be within this INDEX AREA (D/2 x E1/2) A2 A E/2 4 3 (L1) e b TOP VIEW ø1 h FRONT VIEW ø2 h R1 Gauge Plane R L2 ø 8 Pin NSOIC SYMBOL A A1 A2 b c E E1 e h L L1 L2 R R1 ø ø1 ø2 D Seating Plane L JEDEC MS-012 MIN NOM MAX MIN 1.35 0.10 1.25 0.31 0.17 6.00 BSC 3.90 BSC 1.27 BSC 1.75 0.25 1.65 0.51 0.25 0.053 0.004 0.049 0.012 0.007 0.50 1.27 0.010 0.016 8º 15º - 0.003 0.003 0º 5º 0º 0.25 0.40 c Variation AA Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm Dimensions in Millimeters: Controlling Dimension 1.04 REF 0.25 BSC 0.07 0.07 0º 5º 0º 4.90 BSC SIPEX Pkg Signoff Date/Rev: Date: 3/14/06 ø1 NOM SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 11 MAX 0.069 0.010 0.065 0.020 0.010 0.236 BSC 0.154 BSC 0.050 BSC 0.020 0.050 0.041 REF 0.010 BSC 8º 15º 0.193 BSC JL Aug16-05 / Rev A ©Copyright 2006 Sipex Corporation ORDERING INFORMATION Ordering No. Accuracy Output Voltage Packages SPX2945M3-3-3 1% 3.3V 3-Pin SOT-223 SPX2945M3-3-3/TR 1% 3.3V 3-Pin SOT-223 SPX2945M3-5-0 1% 5.0V 3-Pin SOT-223 SPX2945M3-5-0/TR 1% 5.0V 3-Pin SOT-223 SPX2945S-3-3 1% 3.3V 8-Pin NSOIC SPX2945S-3-3/TR 1% 3.3V 8-Pin NSOIC SPX2945S-5-0 1% 5.0V 8-Pin NSOIC SPX2945S-5-0/TR 1% 5.0V 8-Pin NSOIC SPX2945R-3-3 1% 3.3V 3-Pin TO-252 SPX2945R-3-3/TR 1% 3.3V 3-Pin TO-252 SPX2945R-5-0 1% 5.0V 3-Pin TO-252 SPX2945R-5-0/TR 1% 5.0V 3-Pin TO-252 SPX2945T-3-3 1% 3.3V 3-Pin TO-263 SPX2945T-3-3/TR 1% 3.3V 3-Pin TO-263 SPX2945T-5-0 1% 5.0V 3-Pin TO-263 SPX2945T-5-0/TR 1% 5.0V 3-Pin TO-263 SPX2945T5-3-3 1% 3.3V 5-Pin TO-263 SPX2945T5-3-3/TR 1% 3.3V 5-Pin TO-263 SPX2945T5-5-0 1% 5.0V 5-Pin TO-263 SPX2945T5-5-0/TR 1% 5.0V 5-Pin TO-263 SPX2945U-3-3 1% 3.3V 3-Pin TO-220 SPX2945U-5-0 1% 5.0V 3-Pin TO-220 Available in lead free packaging. To order add "-L" suffix to part number. Example: SPX2954S-5-0/TR = standard; SPX2954S-L-5-0/TR = lead free /TR = Tape and Reel Pack quantity is 500 for TO-263, 2,000 for TO-252, and 2,500 for SOT223 or NSOIC. Sipex Corporation Solved By Sipex TM Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Date: 3/14/06 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown 12 ©Copyright 2006 Sipex Corporation