AS2975 180 mA Low Dropout Voltage Regulators FEATURES APPLICATIONS • 5V Fixed & at 180mA Output • Very Low Quiescent Current • Low Dropout Voltage • Extremely Tight Load And Line Regulation • Very Low Temperature Coefficient • Needs Only 1µF For Stability • Current & Thermal Limiting • Unregulated DC Input Can Withstand -20V Reverse Battery And +60V Positive Transients • Similar Replacement For LP2950/LP2951 Sockets • Battery Powered Systems • Cordless Telephones • Radio Control Systems • Portable/Palm Top/Notebook Computers • Portable Consumer Equipment • Portable Instrumentation • Avionics • Automotive Electronics • SMPS Post-Regulator • Voltage Reference AS2975 SO-8 versions only • Error Flag Warns Of Output Dropout • Logic- Controlled Electronic Shutdown • Output Programmable from 1.24 to 29V PRODUCT DESCRIPTION The AS2975 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 AS2975 features very low quiescent current and very low dropout voltage (Typ. 50mV at light load and 380 mV at 180 mA). This includes a tight initial tolerance of 0.5% typ., extremely good load and line regulation 0.05% typ. and very low output temperature coefficient, making the AS2975 useful as a low-power voltage reference. Other additional key features include higher output current (150mA), positive transient protection up to 60V (Load dump), and the ability to survive an unregulated input voltage transient of -20V below ground (reverse battery). The error flag output feature is used as power-on reset for warning of a low output voltage, due to falling voltage input of batteries. Another feature is the logic-compatible shutdown input which enables the regulator to be switched on and off. The AS2975 is offered in a 3-pin TO-92 package compatible with other 5V regulators. The AS2975 is available in 8-pin plastic, SO-8 packages. ORDERING INFORMATION TO-92 3-PIN PLASTIC SOIC 8-PIN AS2975YCN-X AS2975CN-X AS2975YCPX AS2975CP-X X= 3.0V, 3.3V, OR 5.0V Y= Output Tolerance (A = 0.5%, Blank = 1%) PIN CONNECTIONS OPER. TEMP. RANGE -40°C to +125°C -40°C to +125°C -40°C to +125°C -40°C to +125°C 8-Pin Surface Mount (S) VOUT 1 SENSE 2 SHUTDOWN GND 3 AS2975 4 Top View 8 VIN 7 FEEDBACK 6 5V TAP 5 ERROR TO-92 (N) 1 VIN 2 3 GND VOUT Bottom View Rev. 10/6/00 AS2975 ABSOLUTE MAXIMUM RATINGS Power Dissipation..........................................Internally Limited Lead Temp. (Soldering, 5 Seconds) ................................ 260°C Storage Temperature Range ............................ -65° to +150°C Operating Junction Temperature Range (Note 10) AS2975 ..................................................... -55° to +150°C AS2975AC/AS2975C............................... -40° to +125°C Input Supply Voltage (Survival) ......................-20V to +60V Feedback Input Voltage ..................................-1.5V to +30V Shutdown Input Voltage..................................-0.3V to +30V Error Comparator Output ................................-0.3V to +30V ESD Rating ............................................................. 2KV Min ELECTRICAL CHARACTERISTICS at VS=15V, TA=25°C, unless otherwise specified. Boldface apply over the full operating temperature range. PARAMETER CONDITIONS (Note 2) 3.3 V Versions Output Voltage Output Voltage 5 V Versions Output Voltage Output Voltage AS2975 AS2975AC AS2975C Min Typ Max Min Typ Max TJ = 25°C -25°C ≤TJ ≤85°C -40°C ≤TJ≤ +125°C 100 µA ≤IL ≤180 mA TJ ≤TJMAX 3.2835 3.3 3.3165 3.3 3.2604 3.2505 3.3 3.3396 3.3495 3.2835 3.267 3.2608 3.2505 3.3 3.3165 3.333 3.3396 3.3495 TJ = 25°C -25°C ≤TJ ≤85°C -40°C ≤TJ≤ +125°C 100 µA ≤IL ≤180 mA TJ ≤TJMAX 4.975 5.0 5.025 4.94 4.925 5.0 5.06 5.075 4.975 4.95 4.94 4.925 5.0 5.0 5.0 5.0 5.025 5.050 5.06 5.075 Min UNITS Typ Max 3.267 3.2505 3.2604 3.201 3.3 V 3.3 3.333 3.695 3.3396 3.399 4.95 4.925 4.90 4.85 5.0 5.0 5.0 5.0 5.05 5.075 5.10 5.15 V V V All Voltage Options Output Voltage Temperature Coefficient Line Regulation (Note 3) 20 120 20 (Note 1) 6V ≤VIN ≤30V (Note 4) 0.03 0.1 0.03 0.1 0.04 0.2 Load Regulation (Note 3) 100 µA ≤IL ≤ 180 mA 0.04 0.1 0.04 0.1 0.1 0.2 % Dropout Voltage (Note 5) IL = 100µ A IL = 100 mA IL = 180 mA IL = 100 µA IL = 100 mA IL = 180 mA VOUT = 0 50 380 450 150 8 18 130 80 450 500 170 12 22 200 50 380 450 150 8 18 130 80 450 500 170 12 22 200 50 380 450 150 8 18 130 80 450 500 170 12 22 200 mV 0.05 0.2 0.05 0.2 0.05 0.2 Ground Current Current Limit Thermal Regulation Output Noise, 10Hz to 100kHz 8-Pin Versions Only Reference Voltage Reference Voltage 430 160 100 CL = 1µF CL = 200 µF CL = 13.3 µF (Bypass = 0.01 µF pins 7 to 1(AS2975)) 1.22 Over Temperature ( Note 6) AS2975 1.235 1.19 Feedback Pin Bias Current 40 50 430 160 100 430 160 100 1.25 1.22 AS2975AC 1.235 1.25 1.21 1.27 1.19 1.27 1.18 60 40 ppm/°C 60 µA mA mA mA %/W µV rms AS2975C 1.23 40 % 1.26 V 1.28 V 60 nA Reference Voltage Temperature Coefficient Feedback Pin Bias Current Temperature Coefficient Error Comparator (Note 7) Output Leakage Current VOH = 30V 0.01 1 0.01 1 0.01 1 µA Output Low Voltage 150 250 150 250 150 250 mV Upper Threshold Voltage VIN = 4.5V IOL = 400µA (Note 8) Lower Threshold Voltage (Note 8) 40 20 20 50 ppm/°C 0.1 0.1 0.1 nA/°C 60 75 40 95 60 75 40 95 60 75 mV 95 Rev. 10/6/00 mV Hysteresis (Note 8) 15 15 15 mV Rev. 10/6/00 AS2975 PARAMETER CONDITIONS AS2975 (Note 2) Min AS2975AC Typ Max 1.3 0.6 Min AS2975C Min Typ Max 1.3 0.7 Typ Max UNITS 8-Pin Version only (Continued) Shutdown Input Input Logic Voltage Low (Regulator ON) High (Regulator OFF) VS = 2.4V VS = 30V (Note 9) Shut Down Pin Input Current 2 2 30 675 3 1.3 0.7 V 30 675 3 50 800 10 µA 2 50 800 10 30 675 3 50 800 10 Regulator Output Current in µA Shutdown 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 guaranteed for TJ = 25°C, VIN = 6V, IL = 100µA and CL = 1 µF. Additional conditions for the 8-pin versions are feedback tied to 5V 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 AS2975 is tested at 150°C for IL = 1mA. For IL = 100µA 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 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: VREF ≤VOUT ≤ (VIN - 1V), 2.3 ≤VIN≤30V, 100µA≤IL≤ 100 mA, TJ ≤ TJMAX. Note 7: 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 95mV x 5V/1.235 = 384mV. 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 8: VSHUTDOWN ≥ 2V, VIN ≤ 30V, VOUT =0, Feedback pin tied to 5V Tap. Note 9: All typical values are not guaranteed. The value could vary from lot to lot. Note 10: 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 (S) package is 160°C/W. BLOCK DIAGRAM UNREGULATED DC 7 + INPUT FEEDBACK 5V @ 180mA MAX 1 8 OUTPUT 2 SENSE + _ FROM CMOS OR TTL 3 180k Ω .. 6 ERROR AMPLIFIER 330kΩ .. 5V TAP SHUTDOWN 60k Ω .. + + 60 mV _ + 1.23V 5 + 1 µ F.. ______ ERROR ERROR DETECTION COMPARATOR TO CMOS OR TTL 4 REFERENCE GROUND AS2975 Block Diagram Rev. 10/6/00 AS2975 APPLICATION HINTS EXTERNAL CAPACITORS The stability of the AS2975 requires a 1.0µF 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 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 capacitors value may 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 0.33µF and 0.1µF for 1mA. More output capacitance is needed for the 8-pin version at voltages below 5V since it runs the error amplifier at lower gain. At worst case 3.3µF or greater must be used for the condition of 10mA load at 1.23V output. The AS2975, 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. When setting the output voltage of the AS2975, a minimum load of 1µA is recommended 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 1µA tantalum or aluminum electrolytic capacitor should be placed from the input to the ground. Instability can occur if there is stray capacitance to the AS2975 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 100 pF capacitor between output and feedback and increasing the output capacitor to at least 3.3µF. ERROR DETECTION COMPARATOR OUTPUT The Comparator produces a logic low output whenever the AS2975 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 AS2975 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 AS2975 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. 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. PROGRAMMING THE OUTPUT VOLTAGE OF AS2975 The AS2975 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 (5V Tap). Also, 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. Refer to the below equation for the programming of the output voltage: VOUT = VREF × (1 + R1\ R2)+ IFBR1 The Vref is 1.235 and IFB is the feedback bias current, nominally -20nA. The minimum recommended load current of 1µA forces an upper limit of 1.2 MΩ on value of R2. If no load is presented the IFB produces an error of typically 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 AS2975 typically draws 60µA 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 AS2975 but is relatively inefficient, as increasing the capacitor from 1µF to 220µF only decreases the noise from 430µV to 160µV rms 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 CBYPASS ≅ 1 / 2πR1 × 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 100µVRMS 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. Rev. 10/6/00 AS2975 TYPICAL PERFORMANCE CHARACTERISTICS Rev. 10/6/00 AS2975 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Rev. 10/6/00 AS2975 TYPICAL APPLICATIONS 4.75V OUTPUT VOLTAGE +VIN _______ ERROR* 100K 8 ERROR ______ ERROR 5 OUTPUT +VIN VOUT 1.2 to30V 1 AS2975 SHUTDOWN +5.0V INPUT VOLTAGE + R1 SD INPUT + +1.3V 3 3.3uF .01uF FB GND 7 4 1.23V + VREF R2 * See Application Info. _______ Figure 1. ERROR Output Timing Figure 2. Adjustable Regulator +VIN +VIN 470KΩ .. 8 5 470KΩ .. ______ ERROR +VIN VOUT 8 VOUT 1 ERROR 5 OUTPUT AS2975 ______ ERROR +VIN VOUT 1 *VOUT= VIN AS2975 + 3 R1 SD GND 4 FB SHUTDOWN INPUT 7 3 SD GND 4 R2 Latch Off When Error Flag Occurs µF 1µ FB 7 *MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 4mV TO 400 VCURRENT LIMIT IS TYPICALLY DEPENDING ON LOAD CURRENT. 160 A Wide Input Voltage Range Current Limiter Rev. 10/6/00 AS2975 TYPICAL APPLICATIONS (continued) + 6V SEALED LEADACID BATTERY SOURCE Ω 1.5KΩ Ω 120KΩ 8 1N457 +VIN FB AS385 VOUT 1 MAIN V- AS2975 SENSE Ω 400KΩ FOR 5.5 V 3 Ω 100KΩ MEMORY V+ 2 + µF 1µ SD GND 4 Ω 20KΩ NI-CAD BACKUP BATTERY Low Battery Disconnect 8 Ω 39kΩ 2 SENSE +VIN 5 ______ ERROR VOUT RESET 1 + AS2975 - 3 C4 SD FB + Ω 39kΩ 1% GND 4 +VOUT = 5V 1µ µF 7 TAP 6 Ω 100kΩ C1 Ω 100kΩ + 6V LEAD1% ACID BATTERY Ω 1kΩ <5.8V** C2 + Ω 100kΩ <6.0V** 1% Ω 1kΩ C3 + 100κΩ <6.2V** R3 1% Ω 10kΩ * OPTIONAL LATCH OFF WHEN DROPOUT OCCURS. ADJUST R3 FOR C2 SWITCHING WHEN VIN IS 6.0V Ω 20kΩ ** OUTPUTS GO LOW WHEN VIN DROPS BELOW DESIGNATED THRESHOLDS Regulator with State-of-Charge indicator Rev. 10/6/00 AS2975 TYPICAL APPLICATIONS (continued) +VIN 8 3 AUX SHUTDOWN +VIN SD Ω 10KΩ _______ 5 ERROR 5 DEGREE SHUTDOWN FLAG OFF AS2975 ON VOUT FB GND 4 + TEMP SENSOR 1 7 AS35 EXTERNAL CIRCUIT PROTECTED FROM OVER TEMPERATURE (V+ GOES OFF WHEN TEMP > 125) OR RELAY Ω 8.2KΩ System Over Temperature Protection Circuit +5V 4 4.7mA 20mA UNREGULATED INPUT 8 OUTPUT +V IN VOUT 1N4001 5 1 IN VOUT AS2975 FB 0.1uF 7 4 330KΩ .. 27KΩ AS2975 2N5432 .. 2 3 GND 1 360K Ω .. 1N457 MIN VOLTAGE = 4V Open Circuit Detector for 4mA to 20mA Current Loop VTAP FB 7 SENSE GND 4 5V 2 OUTPUT + 4.7uF LOAD 50mA TO 300 mA 300 mA Regulator with 0.75 Dropout Rev. 10/6/00