Advanced Monolithic Systems AMS2950/AMS2951 150mA LOW DROPOUT VOLTAGE REGULATOR FEATURES APPLICATIONS • 5.0V, 3.3V, 3.0V and 2.5V Versions • 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 (1µ µ F) 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 (AMS2951 ONLY) • 1.24V to 29V Programmable Output • Error Flag Warning of Voltage Output Dropout • Logic Controlled Electronic Shutdown GENERAL DESCRIPTION The AMS2950 and AMS2951 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 150mA) thus prolonging battery life. The quiescent current increases only slightly in dropout. The AMS2950/AMS2951 has positive transient protection up to 60V and can survive unregulated input transient up to 20V below ground. The AMS2950 and AMS2951 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 AMS2950 is offered in the 3-pin TO-92 package. AMS2951 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 AMS2951 also features the logic-compatible shutdown input which enables the regulator to be switched on and off. The AMS2951 device may be pin-strapped for a 5.0V, 3.3V, 3.0V or 2.5 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 AMS2950ACN-X AMS2951ACP- AMS2951ACS-X AMS2950CN-X AMS2951CP-X AMS2951CS-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, 3.0V, 2.5V 5 ERROR Top View TO-92 OUTPUT INPUT GND Bottom View Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage SHUTDOWN Input Voltage, Error Comparator Output Voltage,(Note 9) FEEDBACK Input Voltage (Note 9) (Note 10) Power Dissipation Junction Temperature Storage Temperature Soldering Dwell Time, Temperature -0.3 to +30V Wave Infrared Vapor Phase ESD 4 seconds, 260°C 4 seconds, 240°C 4 seconds, 219°C TBD -1.5 to +30V OPERATING RATINGS (Note 1) Internally Limited +150°C -65°C to +150°C Max. Input Supply Voltage Junction Temperature Range (TJ) (Note 8) AMS2950AC-XX, AMS2950C-XX AMS2951AC-XX, AMS2951C-XX 30V -40°C to +125°C ELECTRICAL CHARACTERISTICS at Vs=Vout+1V, Ta=25°C, unless otherwise noted. Parameter AMS2950AC AMS2951AC Conditions (Note 2) Min. Typ. AMS2950C AMS2951C Max. Min. Typ. Units Max. 2.5 V Versions (Note 16) Output Voltage TJ = 25°C (Note 3) Output Voltage Full Operating Temperature Range 100 µA ≤IL ≤150 mA -25°C ≤TJ ≤85°C TJ ≤TJMAX 2.488 2.5 2.512 2.475 2.5 2.525 V 2.475 2.5 2.525 2.450 2.5 2.550 V 2.470 2.5 2.530 2.440 2.5 2.560 V 2.463 2.5 2.537 2.448 2.5 2.562 V 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 3.0 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 ≤150 mA TJ ≤TJMAX 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 ≤150 mA TJ ≤TJMAX 5.0 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 ≤150 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 ≤ 150 mA 0.04 0.1 0.1 0.2 % Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 ELECTRICAL CHARACTERISTICS (Note 2) (Continued) PARAMETER AMS2950AC AMS2951AC CONDITIONS (Note 2) Dropout Voltage (Note 5) Ground Current Min. Typ. AMS2950C AMS2951C Max. Min. Typ. Max. Units IL = 100µ A 50 80 50 80 mV IL = 150 mA 380 450 380 450 mV IL = 100 µA 75 120 75 120 IL = 150 mA 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 Output Noise, 10Hz to 100KHz CL = 1µF CL = 200 µF 430 430 µV rms 160 160 µV rms 100 100 µV rms AMS2951AC AMS2951C CL = 13.3 µF (Bypass = 0.01 µF pins 7 to 1(AMS2951)) 8-Pin Versions only Reference Voltage Reference Voltage 1.22 Over Temperature (Note 7) Feedback Pin Bias Current Reference Voltage Temperature Coefficient 1.26 V 1.285 V 60 nA 20 50 ppm/°C 0.1 0.1 nA/°C 40 V OH = 30V 1.21 1.27 1.185 60 1.235 40 0.01 1 0.01 1 µA 150 250 150 250 mV 95 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 ( Note 12 ) Feedback Pin Bias Current Temperature Coefficient Error Comparator Output Leakage Current 1.235 1.19 40 Low (Regulator ON) High (Regulator OFF) 60 1.3 40 95 60 75 mV 15 0.7 2 mV 1.3 0.7 V 2 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 = T J = 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≤ 150 mA, TJ ≤ TJMAX. Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 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. 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 AMS2951 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 AMS2950 devices have the nominal output voltage coded as the last two digits of the part number. In the AMS2951 products, the 2.5V 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 AMS2950-XX AMS2951-XX VOUT I L≤ 150mA UNREGULATED DC UNREGULATED DC + INPUT 7 FEEDBACK + VOUT IL≤ 150mA OUTPUT 8 INPUT 2 + - + SENSE + ERROR AMPLIFIER 1.23V REFERENCE + SEE APPLICATION HINTS FROM CMOS OR TTL - 3 SHUTDOWN + 50mV ERROR AMPLIFIER + 1.23V REFERENCE + 6 VTAP 5 + - GROUND 1 OUTPUT SEE APPLICATION HINTS 330kΩ TO CMOS OR TTL ERROR 4 GROUND ERROR DETECTION COMPARATOR Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current Input Current Dropout Characteristics 10 6 250 225 1 0.1 0.01 0.1 1 10 LOAD CURRENT (mA) 4 RL= 50Ω 2 1 1 6 2 3 4 5 6 7 8 INPUT VOLTAGE (V) 50 0 1 9 10 5.0 4.98 0.2% 4.96 QUIESCENT CURRENT (µA) 5.02 120 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 7 INPUT VOLTAGE (V) 8 Quiescent Current 8 5V OUTPUT 5V OUTPUT 9 VIN= 6V IL= 150mA 8 7 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) QUIESCENT CURRENT (µA) 90 QUIESCENT CURRENT (mA) VIN= 6V 100 9 10 140 Quiescent Current IL= 100µA 2 3 4 5 6 7 8 INPUT VOLTAGE (V) Quiescent Current 10 5V OUTPUT RL= ∞ 75 5V OUTPUT 5.04 Quiescent Current QUIESCENT CURRENT (µA) 125 100 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 270 240 210 180 150 120 90 75 60 45 30 15 0 RL= 50 kΩ 3 0 150 INPUT CURRENT (µA) OUTPUT VOLTAGE (V) GROUND CURRENT (mA) 5V OUTPUT 5 7 6 5 IL= 150mA 4 3 2 1 0 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 8 AMS2950/AMS2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Short Circuit Current 150 140 130 120 110 500 400 IL= 150mA 300 ~ ~ 100 50 IL= 100µA 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) AMS2951 Minimum Operating Voltage 1.7 TJ = 25°C 100 0 -10 -20 1mA 10mA OUTPUT CURRENT 150mA AMS2951 Feedback Pin Current FEEDBACK CURRENT (µA) 1.8 200 50 10 1.9 300 AMS2951 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 AMS2951 Error Comparator Output AMS2951 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) Advanced Monolithic Systems, Inc. 8 SINK CURRENT (mA) VOUT= 5V 8 -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) 2.0 TA = 125°C 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) 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 0 200 400 TIME (µs) 600 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 800 AMS2950/AMS2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 150 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 10K 100K 100 1K FREQUENCY (Hz) 20 101 1M IL= 50mA IL= 150mA 50 40 CL= 1µF VIN= 6V 30 VOUT= 5V 20 10 101 105 104 10 20 101 6 102 105 103 104 FREQUENCY (Hz) Advanced Monolithic Systems, Inc. 106 5V OUTPUT IL= 150mA CL= 1 µF 2.5 2.0 1.5 CL= 3.3 µF CL= 220 µF 1.0 0.0 105 104 103 FREQUENCY (Hz) 106 AMS2951 Divider Resistance 3.0 0.5 102 400 3.5 VOLTAGE NOISE SPECTRAL DENSITY(mV/√Hz) 60 103 AMS2951 Output Noise Ripple Rejection 70 102 FREQUENCY (Hz) 80 RIPPLE REJECTION (dB) 8 12 TIME (ms) PIN 2 TO PIN 4 RESISTANCE (kΩ) 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) 0 150 mA 100 µA AMS2951 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 7 102 103 104 FREQUENCY (Hz) 105 300 200 100 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 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) 120 30 25 20 15 10 5 0 OUTPUT CURRENT (mA) 1.8 1.4 AMS2951 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 TJ = 125° C IL= 100µA 10 15 20 25 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 0 30 10 5 15 20 INPUT VOLTAGE (V) 25 Thermal Response 120 80 100 0 5 AMS2950 Maximum Rated Output Current 100 8 PIN MOLDED DIP SOLDERED TO PC BOARD 5 4 2 0 -2 1 ~ ~ 1.25W 0 -1 0 10 20 30 TIME (µs) 40 50 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 30 AMS2950/AMS2951 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 200mA load at 1.23V output (Output shorted to Feedback) a 3.3µF (or greater) capacitor should be used. Unlike many other regulators, the AMS2950, 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 AMS2951 version with external resistors, a minimum load of 1µA is recommended. A 1µF tantalum or aluminum electrolytic capacitor should be placed from the AMS2950/AMS2951 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 AMS2951 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. Since the AMS2951’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 pull-up 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 (AMS2951) The AMS2951 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 AMS2951 typically draws 60 µA at no load with Pin 2 open-circuited, this is a small price to pay. Reducing Output Noise Error Detection Comparator Output The comparator produces a logic low output whenever the AMS2951 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). 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 AMS2951 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 ). Advanced Monolithic Systems, Inc. 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 AMS2950 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. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 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 AMS2951 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 k suggested), to ensure a lowlevel 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 VTAP FB 7 SENSE 2N5432 (2) 8 27kΩ AMS2951 6 330Ω 1 5V OUTPUT 2 GND 4 +VIN 4.7µF LOAD 50mA TO 300mA ERROR OUPUT 5 ERROR VOUT 1 *VOUT ≈ VΙΝ AMS2951 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 Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 TYPICAL APPLICATIONS (Continued) Low Drift Current Source 30V +V = 2 IL 5Volt Current Limiter LOAD 5V BUS 8 +VIN VIN VOUT 1 *VOUT ≈ 5V AMS2950 -5.0 VOUT AMS2951 SHUTDOWN 3 SD INPUT 1µF 0.1µF GND FB 4 7 R 1% 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 +5V +VIN C - MOS GATE *SLEEP INPUT 4.7kΩ 4 20mA *OUTPUT 1 8 47kΩ 470kΩ +VIN 8 VOUT +VIN ERROR OUPUT 5 ERROR SHUTDOWN 3 SD INPUT +VOUT VOUT 1 GND FB 4 7 4 7 FB 200kΩ 100pF 1% + 2N3906 100kΩ 1% 100kΩ Advanced Monolithic Systems, Inc. 1 AMS2951 1N4001 AMS2951 5 3.3µF 0.1µF 2 GND 4 1N457 360 MIN. VOLTAGE ≈ 4V 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 TYPICAL APPLICATIONS (Continued) 2 Ampere Low Dropout Regulator CURRENT LIMIT SECTION Regulator with Early Warning and Auxiliary Output +VIN +VIN = VOUT +.5V 8 +VIN 0.05 680 6 470 7 4.7MΩ FB VOUT 7 FB GND VOUT 4 1 ERROR FLAG 5 AMS2951 220 1µF 3.6V NICAD 4 27 kΩ ERROR SD 20 + GND +VIN 3 5V MEMORY SUPPLY D2 1 AMS2951 #1 5 ERROR +VOUT @ 2A 10kΩ 8 2 SENSE VTAP MJE2955 2N3906 D1 + R1 + 4.7 TANT. 100µF EARLY WARNING D3 2.7MΩ D4 1% R2 Q1 20kΩ 8 +VIN 6 .033 2 SENSE VTAP 7 VOUT FB AMS2951 #2 5 SD ERROR 3 RESET 330 kΩ MAIN 5V OUTPUT + 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 10kΩ 1µF 0.01µF SUPERTEX VP12C 470kΩ 8 IN 6 VTAP 1ΜΩ FB + VOUT 3 SD R1 FB GND 4 VOUT 1 AMS2951 RESET 0.002µF +VIN ERROR 470kΩ 220µF 1 OUT GND 4 OUTPUT 5V ± 1% @ 0 TO 1A 2 SENSE AMS2951 7 8 5 7 + 1µF R2 2kΩ IQ ≅ 400µA Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 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. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 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. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140