Low Drop Out Voltage Regulator

www.DataSheet4U.com ® SPX2945 400mA Low Dropout Voltage Regulator with Shutdown FEATURES ■ Output 3.3V, 5.0V at 400mA Output ■ Very Low Quiescent Current, 100µA ■ Low Dropout Voltage, 420mV at 400mA ■ Extremely Tight Load and Line Regulation ■ Very Low Temperature Coefficient ■ Current & Thermal Limiting ■ Error Flag Warns Of Output Dropout ■ Logic-Controlled Electronic Shutdown ■ Output Programmable From 1.24V to 20V (for SO-8) VIN IN OUT ON SHUTDOWN INPUT OFF +VIN 100K 8 +VIN VOUT + 7 R1 0.01µF 10µF 1 1.2V to 20V SPX2945 3 SD GND 4 FB ______ ERROR ERROR 5 R2 VREF OUTPUT Adjustable Regulator 5V SPX2945 + 0.1 µF GND + 2.2 µF 5V Regulator Circuit 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) TO-263-5 (T5) TO-252 (R) VOU 8-Pin Surface Mount (S) SOT-223 (M3) SPX2945 SPX2945 1 1 2 3 2 3 1 2 3 4 8 7 6 5 SPX2945 5 Pin TO-263 SPX2945 1 2 3 SPX2945 SENS SHUTDOWN V IN FEEDBACK 5V/ 3.3V TAP ERRO SPX2945 1 2 3 1 2 3 4 5 V IN GN V IN GN VOU VOU GN VIN GN V OU VIN GN VOU Rev. B Date:01/20/04 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown GND VOUT VIN SD Er ©Copyright 2004 Sipex Corporation 1 ABSOLUTE MAXIMUM RATINGS 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 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 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 3.3V Version Output Voltage 1mA ≤ IL ≤ 400mA 5.0V Version Output Voltage 1mA ≤ IL ≤ 400mA All Voltage Options Output Voltage Temperature Coefficient Line Regulation (Note 3) Load Regulation (Note 3) Dropout Voltage (Note5) 20 (Note1) 6V ≤ VIN ≤ 20V (Note 4) IL=1 to 400mA IL=1mA IL=400mA Ground Current IL=1mA IL=150mA IL=300mA IL=400mA Current Limit Thermal Regulation Output Noise, 10Hz to 100kHz, IL=100mA PSRR at 100KHz IL=100mA Reference Voltage Reference Voltage Feedback Pin Bias Current Reference Voltage Temp. Coefficient Rev. B Date:01/20/04 CONDITIONS (Note 2) MIN TYP MAX UNITS 3.267 3.217 4.950 4.880 3.3 3.3 5.0 5.0 3.333 3.382 5.050 5.120 100 V ♦ V ♦ ♦ ♦ ♦ mV ♦ ♦ µA ♦ mA ♦ ♦ ♦ ♦ mA %/W µVRMS dB ppm/°C mV mV 1.5 6 60 360 100 2 4 8 330 0.05 400 260 31 20 20 30 100 150 450 700 200 300 4 6 8 12 15 25 800 0.2 VOUT=0 CL=2.2µF CL=33µF CL=10µF 1.210 Over Temperature 1.185 Adjustable 8 Pin Version only 1.235 20 20 1.260 1.285 40 60 ♦ ppm/°C V V nA SPX2945 400mA Low Dropout Voltage Regulator with Shutdown ©Copyright 2004 Sipex Corporation 2 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 Feedback Pin Bieas Current Temperature Coefficient Output Leakage Current Output Low Voltage Upper Threshold Voltage Lower Threshold Voltage Hysteresis Input Logic Voltage Shutdown Pin Input Current V0H=20V VIN=4.5V I0L=400µA (Note 6) (Note 6) (Note 6) Low (Regulator ON) High (Regulator OFF) VS=2.4V VS=26V Regulator Output Current in Shutdown (Note 7) 10 20 40 25 CONDITIONS (Note 2) MIN TYP 0.1 0.01 150 60 75 15 1.3 30 450 3 ♦ 0.7 2.0 50 100 600 750 ♦ ♦ ♦ ♦ µA 95 140 1 2 250 400 MAX ♦ UNITS nA/°C µA ♦ mV ♦ mV mV ♦ mV V µA 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. Rev. B Date:01/20/04 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown ©Copyright 2004 Sipex Corporation 3 SPX2945 - 5.0V BLOCK DIAGRAM UNREGULATED DC 7 FEEDBACK + 8 INPUT 1 OUTPUT 5V at 400mA MAX 2 SENSE + _ FROM CMOS OR TTL 3 SHUTDOWN 180kΩ ERROR AMPLIFIER . 6 5V TAP 330kΩ . + 5 ______ ERROR 1µF TO CMOS OR TTL 4 60kΩ . + 60 mV + 1.23V + _ ERROR DETECTION COMPARATOR 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. 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. 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. This problem can be fixed by adding a 100pF capacitor between output and feedback and increasing the output capacitor to at least 3.3µF. Rev. B Date:01/20/04 SPX2945 400mA Low Dropout Voltage Regulator with Shutdown ©Copyright 2004 Sipex Corporation 4 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. Th