AMS2951

Advanced Monolithic Systems FEATURES • 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 F) for Stability • Unregulated DC Positive Transients 60V • 1.24V to 29V Programmable Output • Error Flag Warning of Voltage Output Dropout • Logic Controlled Electronic Shutdown AMS2950/AMS2951 150mA LOW DROPOUT VOLTAGE REGULATOR APPLICATIONS • 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) 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 PACKAGE TYPE TO-92 8 LEAD PDIP 8 LEAD SOIC AMS2950ACN-X AMS2951ACP- AMS2951ACS-X AMS2950CN-X AMS2951CP-X AMS2951CS-X X = 3.3V, 3.0V, 2.5V OPERATING TEMP. RANGE IND. IND PIN CONNECTION 8L SOIC/ 8L PDIP OUTPUT 1 SENSE 2 SHUTDOWN 3 GROUND 4 8 INPUT 7 FEEDBACK 6 VTAP 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 2.5 V Versions (Note 16) Output Voltage TJ = 25°C (Note 3) -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µ A ≤IL ≤150 mA TJ ≤TJMAX TJ = 25°C (Note 3) 2.488 2.475 2.470 2.463 2.5 2.5 2.5 2.5 2.512 2.525 2.530 2.537 2.475 2.450 2.440 2.448 2.5 2.5 2.5 2.5 2.525 2.550 2.560 2.562 V V V V Conditions (Note 2) AMS2950AC AMS2951AC Min. Typ. Max. Min. AMS2950C AMS2951C Typ. Max. Units Output Voltage 3.0 V Versions (Note 16) Output Voltage -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µ A ≤IL ≤150 mA TJ ≤TJMAX 2.985 2.970 2.964 2.958 3.0 3.0 3.0 3.0 3.015 3.030 3.036 3.042 2.970 2.955 2.940 2.928 3.0 3.0 3.0 3.0 3.030 3.045 3.060 3.072 V V V V Output Voltage 3.3 V Versions (Note 16) Output Voltage TJ = 25°C (Note 3) -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µ A ≤IL ≤150 mA TJ ≤TJMAX 3.284 3.267 3.260 3.254 3.3 3.3 3.3 3.3 3.317 3.333 3.340 3.346 3.267 3.251 3.234 3.221 3.3 3.3 3.3 3.3 3.333 3.350 3.366 3.379 V V V V Output Voltage 5.0 V Versions (Note 16) Output Voltage TJ = 25°C (Note 3) -25°C ≤TJ ≤85°C Full Operating Temperature Range 100 µ A ≤IL ≤150 mA TJ ≤TJMAX 4.975 4.95 4.94 4.925 5.0 5.0 5.0 5.0 5.025 5.050 5.06 5.075 4.95 4.925 4.90 4.88 5.0 5.0 5.0 5.0 5.05 5.075 5.10 5.12 V V V V Output Voltage All Voltage Options Output Voltage Temperature Coefficient Line Regulation (Note 14) Load Regulation (Note 14) (Note 12) (Note 4) 6V ≤Vin ≤30V (Note 15) 100 µ A ≤IL ≤ 150 mA 20 0.03 0.04 0.1 0.1 50 0.04 0.1 0.2 0.2 ppm/°C % % 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 Dropout Voltage (Note 5) Ground Current CONDITIONS (Note 2) IL = 100µ A IL = 150 mA IL = 100 µ A IL = 150 mA AMS2950AC AMS2951AC Min. Typ. 50 380 75 8 160 0.05 430 160 100 AMS2951AC 1.22 1.235 1.25 1.27 40 20 60 1.21 1.185 Max. 80 450 120 12 200 0.2 Min. AMS2950C AMS2951C Typ. 50 380 75 8 160 0.05 430 160 100 AMS2951C 1.235 1.26 1.285 40 60 50 Max. 80 450 120 12 200 0.2 Units mV mV µA mA mA %/W µ V rms µ V rms µ V rms Current Limit Thermal Regulation Output Noise, 10Hz to 100KHz Vout = 0 (Note 13) CL = 1µ F CL = 200 µ F CL = 13.3 µ F (Bypass = 0.01 µ F pins 7 to 1(AMS2951)) 8-Pin Versions only Reference Voltage Reference Voltage Feedback Pin Bias Current Reference Voltage Temperature Coefficient Feedback Pin Bias Current Temperature Coefficient Error Comparator Output Leakage Current Output Low Voltage Upper Threshold Voltage Lower Threshold Voltage Hysteresis Shutdown Input Input logic Voltage Shutdown Pin Input Current (Note 3) Regulator Output Current in Shutdown (Note 3) V OH V V nA ppm/°C Over Temperature (Note 7) 1.19 ( Note 12 ) 0.1 0.1 nA/°C = 30V 0.01 150 40 60 75 15 1 250 40 95 0.01 150 60 75 15 1 250 µA mV mV Vin = 4.5V IOL = 400µ A (Note 6) (Note 6) (Note 6) Low (Regulator ON) High (Regulator OFF) Vs = 2.4V Vs = 30V (Note 11) 95 mV mV 1.3 2 30 450 3 0.7 2 50 600 10 1.3 30 450 3 0.7 50 600 10 V V µA µA 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 µ A and CL = 1 µ F for 5V versions and 2.2µ F 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, 100µ A≤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 µ A 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 UNREGULATED DC UNREGULATED DC VOUT I L≤ 150mA 8 INPUT 1 OUTPUT 2 + SENSE ERROR AMPLIFIER 6 VTAP 5 ERROR 4 GROUND + 330k Ω TO CMOS OR TTL SEE APPLICATION HINTS + INPUT OUTPUT + ERROR AMPLIFIER + SEE APPLICATION HINTS VOUT IL≤ 150mA + 7 FEEDBACK FROM CMOS OR TTL 3 SHUTDOWN + 50mV + - + - + 1.23V REFERENCE GROUND 1.23V REFERENCE 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 10 GROUND CURRENT (mA) OUTPUT VOLTAGE (V) 6 Dropout Characteristics 5V OUTPUT Input Current 250 225 INPUT CURRENT (µ A) 200 175 150 125 100 75 50 25 0 RL= ∞ 5V OUTPUT RL= 50 kΩ 5 4 3 RL= 50Ω RL= 50 kΩ 1 0.1 2 1 0 0.01 0.1 1 10 LOAD CURRENT (mA) 150 0 1 2 3 4 5 INPUT VOLTAGE (V) 6 0 1 2345678 INPUT VOLTAGE (V) 9 10 Input Current 270 240 210 180 150 120 90 75 60 45 30 15 0 5.06 5V OUTPUT Temperature Drift of 3 Representative Units 160 5V OUTPUT Quiescent Current 5V OUTPUT OUTPUT VOLTAGE (V) INPUT CURRENT (mA) 5.04 5.02 5.0 4.98 4.96 0.2% QUIESCENT CURRENT (µ A) 140 120 100 80 IL= 0 IL= 1 mA RL= 50Ω 60 40 20 0 0 1 234567 INPUT VOLTAGE (V) 8 0 1 2345678 INPUT VOLTAGE (V) 9 10 4.94 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) Quiescent Current 120 QUIESCENT CURRENT (mA) QUIESCENT CURRENT (µ A) 5V OUTPUT Quiescent Current 10 VIN= 6V Quiescent Current 8 QUIESCENT CURRENT (µ A) 5V OUTPUT 110 100 90 80 70 60 IL= 100µA 5V OUTPUT 7 6 5 4 3 2 1 0 0 1 234567 INPUT VOLTAGE (V) 8 IL= 150mA 9 VIN= 6V IL= 150mA 8 50 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 7 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Short Circuit Current 170 SHORT CIRCUIT CURRENT (mA) DROPOUT VOLTAGE (mV) 160 150 140 130 120 110 100 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 600 500 400 300 Dropout Voltage 500 DROPOUT VOLTAGE (mV) 400 300 200 Dropout Voltage IL= 150mA ~ ~ 100 50 IL= 100µA TJ = 25°C 100 0 100µ A 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) 1mA 10mA OUTPUT CURRENT 150mA AMS2951 Minimum Operating Voltage MINIMUM OPERATING VOLTAGE (V) 2.2 2.1 2.0 1.9 1.8 1.7 1.6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) BIAS CURRENT (nA) 20 AMS2951 Feedback Bias Current 50 FEEDBACK CURRENT (µ A) 0 -50 AMS2951 Feedback Pin Current PIN 7 DRVEN BY EXTERNAL SOURCE (REGULATOR RUN OPEN LOOP) 10 0 -10 TA = 125°C -100 -150 TA = 25°C -20 -30 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) -200 TA = -55°C -250 -2.0 0 0.5 -1.5 -1.0 -0.5 FEEDBACK VOLTAGE (V) 1.0 AMS2951 Error Comparator Output 9 8 ERROR OUTPUT (V) 7 6 5 4 3 2 1 0 0 1 234567 INPUT VOLTAGE (V) 8 50k RESISTOR TO VOUT HYSTERESIS 50k RESISTOR TO EXTERNAL 5V SUPPLY VOUT= 5V AMS2951 Comparator Sink Current INPUT OUTPUT VOLTAGE VOLTAGE CHANGE 2.5 2.0 1.5 TA = 25°C TA = 125°C SINK CURRENT (mA) 100 mV 50 mV 0 -50 mV 8V 6V 4V Line Transient Response CL= 1µF IL= 1mA 1.0 TA = -55°C ~ ~ VOUT= 5V 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) 0 200 400 TIME (µ s) 600 800 Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Load Transient Response 250 200 150 100 50 0 -50 -100 80 60 40 20 0 -20 -40 -60 OUTPUT VOLTAGE CHANGE (mV) OUTPUT VOLTAGE CHANGE (mV) Load Transient Response OUTPUT VOLTAGE (V) 7 6 5 4 3 2 1 0 2 AMS2951 Enable Transient CL= 1 µF CL= 10 µF VOUT = 5V CL= 10 µF IL= 10 mA VIN = 8V VOUT = 5V LOAD CURRENT 150 mA 100 µA 0 1 2 3 TIME (ms) 4 5 LOAD CURRENT ~ ~ ~ ~ 150 mA 100 µA 0 4 8 12 TIME (ms) 16 20 SHUTDOWN PIN VOLTAGE (V) RIPPLE REJECTION (dB) CL= 1 µF VOUT = 5V ~ ~ 0 -2 -100 0 100 200 300 400 500 600 700 TIME (µ s) Output Impedance 10 5 OUPUT IMPEDANCE (Ω) 2 1 0.5 0.2 0.1 0.05 0.02 0.01 10 10K 100K 100 1K FREQUENCY (Hz) 1M VOUT = 5V CL= 1 µF IO= 100mA IO= 1 mA Ripple Rejection 90 90 80 70 60 50 40 30 Ripple Rejection IO= 100µA RIPPLE REJECTION (dB) 80 70 60 50 40 30 20 101 CL= 1 µF VIN= 6V VOUT = 5V IL= 100µA IL= 0 IL= 1mA CL= 1 µF VIN= 6V VOUT = 5V IL= 10mA 102 103 104 105 10 6 20 101 102 FREQUENCY (Hz) 105 104 103 FREQUENCY (Hz) 106 Ripple Rejection 80 RIPPLE REJECTION (dB) 70 60 50 40 30 20 10 101 102 105 103 104 FREQUENCY (Hz) 106 CL= 1µF VIN= 6V VOUT= 5V AMS2951 Output Noise 3.5 VOLTAGE NOISE SPECTRAL DENSITY(mV/√Hz) 400 5V OUTPUT IL= 150mA AMS2951 Divider Resistance PIN 2 TO PIN 4 RESISTANCE (kΩ) 105 IL= 50mA 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0.01 µF BYPASS PIN 1 TO PIN 7 CL= 3.3 µF CL= 220 µF CL= 1 µF IL= 150mA 300 200 100 102 103 104 FREQUENCY (Hz) 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Shutdown Treshold Voltage SHUTDOWN TRESHOLD VOLTAGE (V) OUTPUT VOLTAGE CHANGE (V) 1.8 1.6 1.4 1.2 1.0 0.8 0.6 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (° C) REGULATOR ON REGULATOR OFF Line Regulation 30 25 20 15 10 5 0 120 IL= 100µA TJ = 150° C IL= 1mA AMS2951 Maximum Rated Output Current 8 PIN MOLDED DIP SOLDERED TO PC BOARD TJMAX= 125° C VOUT = 5V TA= 25° C TA= 50° C OUTPUT CURRENT (mA) 100 80 60 40 20 0 ~ ~ 10 5 0 -5 -10 TJ = 125° C IL= 100µA TA= 85° C 5 10 15 20 25 INPUT VOLTAGE (V) 30 0 10 5 15 20 INPUT VOLTAGE (V) 25 30 AMS2950 Maximum Rated Output Current TO-92 PACKAGE .25"LEADS SOLDERED TO PC BOARD TJMAX= 125° C Thermal Response POWER OUTPUT VOLTAGE DISSIPATION (W) CHANGE (mV) 5 4 2 0 -2 1 0 -1 0 10 20 30 TIME (µ s) 40 50 120 OUTPUT CURRENT (mA) 100 80 60 TA= 25° C 40 20 0 0 10 5 15 20 INPUT VOLTAGE (V) 25 30 TA= 85° C ~ ~ 1.25W Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 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. 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 ). 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. 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 Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140 AMS2950/AMS2951 APPLICATION HINTS (Continued) +VIN OUTPUT VOLTAGE 4.75V 100k ERROR* ERROR OUPUT **SHUTDOWN INPUT 5 ERROR* 3 8 +VIN VOUT 1 VOUT 1.2 30V AMS2951 SD GND 4 FB 7 R1 INPUT VOLTAGE 1.3V 5V *+ .01 µF 3.3µF 1.23V VREF R2 FIGURE 1. ERROR Output Timing *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. FIGURE 2. Adjustable Regulator *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 UNREGULATED INPUT 8 IN AMS2951 6 VTAP FB 7 SENSE GND 4 2 4.7µ F OUT 1 330Ω 27 kΩ 5V OUTPUT LOAD 50mA TO 300mA 2N5432 (2) Wide Input Voltage Range Current Limiter +VIN 8 +VIN 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 +V = 2 IL 30V 5Volt Current Limiter LOAD 5V BUS 8 VIN VOUT 1 AMS2951 SHUTDOWN 3 SD INPUT GND 4 R 1% FB 7 1µF + 0.1µF +VIN AMS2950 -5.0 VOUT 1µF GND *VOUT ≈ 5V *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 +VIN *SLEEP INPUT 47kΩ 8 +VIN ERROR OUPUT 5 ERROR VOUT 1 +VOUT C - MOS GATE Open Circuit Detector for 4 to 20mA Current Loop +5V 4.7kΩ 4 20mA 1 8 *OUTPUT 5 470kΩ +VIN VOUT AMS2951 1N4001 200kΩ FB 3.3µF 0.1µF GND 4 1N457 360 7 2 1 4 SHUTDOWN 3 SD INPUT AMS2951 100pF FB 7 2N3906 4 1% + GND 100kΩ 1% 100kΩ MIN. VOLTAGE ≈ 4V Advanced Monolithic Systems, Inc. 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 8 +VIN 6 VTAP 2 SENSE VOUT 1 D2 5V MEMORY SUPPLY +VIN = VOUT +.5V D1 680 0.05 470 7 2N3906 4.7MΩ 8 +VIN ERROR AMS2951 3 SD GND 4 20kΩ .033 FB VOUT 1 5 ERROR FLAG 7 R1 1% R2 Q1 6 7 3 + + 4.7 TANT. 100µF 2.7MΩ 10kΩ MJE2955 +VOUT @ 2A FB AMS2951 #1 5 ERROR GND 4 27 kΩ D3 D4 + 20 1µF 3.6V NICAD EARLY WARNING 220 8 +VIN VTAP 2 SENSE VOUT 330 kΩ MAIN 5V OUTPUT RESET µP VDD FB AMS2951 #2 5 SD ERROR GND 4 + 1µF 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 UNREGULATED INPUT 1µF 10kΩ 0.01µF SUPERTEX VP12C 8 IN 6 VTAP SENSE AMS2951 7 FB GND 4 OUT 1 2kΩ IQ ≅ 400µA 2 + 220µF OUTPUT 5V ± 1% @ 0 TO 1A Latch Off When Error Flag Occurs +VIN 470kΩ 5 470kΩ 8 +VIN ERROR VOUT 1 VOUT AMS2951 3 SD RESET GND 4 FB 7 R1 + R2 1µF 1ΜΩ 0.002µF 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) 0.060±0.005 (1.524±0.127) DIA 0.180±0.005 (4.572±0.127) 0.060±0.010 (1.524±0.254) 0.140±0.010 (3.556±0.127) 0.180±0.005 (4.572±0.127) 0.90 (2.286) NOM 5° NOM 0.500 (12.70) MIN 10° NOM 0.050 (1.270) MAX UNCONTROLLED LEAD DIMENSIONS 0.050±0.005 (1.270±0.127) 0.016±0.003 (0.406±0.076) 0.015±0.002 (0.381±0.051) 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 0.053-0.069 (1.346-1.752) 0.004-0.010 (0.101-0.254) 0.008-0.010 (0.203-0.254) 0.010-0.020 x 45° (0.254-0.508) 0°-8° TYP 0.014-0.019 (0.355-0.483) 0.050 (1.270) 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 0.255±0.015* (6.477±0.381) 1 2 3 4 0.045-0.065 (1.143-1.651) 0.130±0.005 (3.302±0.127) 0.300-0.325 (7.620-8.255) 0.065 (1.651) TYP 0.005 (0.127) MIN 0.100±0.010 (2.540±0.254) 0.125 (3.175) MIN 0.018±0.003 (0.457±0.076) 0.015 (0.380) MIN 0.009-0.015 (0.229-0.381) 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