LM2941/LM2941C 1A Low Dropout Adjustable Regulator and the load. Familiar regulator features such as short circuit and thermal overload protection are also provided. General Description The LM2941 positive voltage regulator features the ability to source 1A of output current with a typical dropout voltage of 0.5V and a maximum of 1V over the entire temperature range. Furthermore, a quiescent current reduction circuit has been included which reduces the ground pin current when the differential between the input voltage and the output voltage exceeds approximately 3V. The quiescent current with 1A of output current and an input-output differential of 5V is therefore only 30mA. Higher quiescent currents only exist when the regulator is in the dropout mode (VIN - VOUT 3V). Designed also for vehicular applications, the LM2941 and all regulated circuitry are protected from reverse battery installations or two-battery jumps. During line transients, such as load dump when the input voltage can momentarily exceed the specified maximum operating voltage, the regulator will automatically shut down to protect both the internal circuits Features LLP space saving package Output voltage adjustable from 5V to 20V Dropout voltage typically 0.5V @ IO = 1A Output current in excess of 1A Trimmed reference voltage Reverse battery protection Internal short circuit current limit Mirror image insertion protection P+ Product Enhancement tested TTL, CMOS compatible ON/OFF switch Connection Diagram and Ordering Information TO-220 Plastic Package TO-263 Surface-Mount Package 882302 Top View Order Number LM2941T or LM2941CT See NS Package Number TO5A 882308 Order Number LM2941S, LM2941SX or LM2941CS, LM2941CSX See NS Package Number TS5B 8-Lead LLP Surface Mount Package 882333 Top View Ordering Number LM2941LD, LM2941LDX See NS Package Number LDC08A (c) 2012 Texas Instruments Incorporated 8823 SNVS770F www.ti.com LM2941/LM2941C 1A Low Dropout Adjustable Regulator March 9, 2012 LM2941/LM2941C Absolute Maximum Ratings (Note 1) Operating Ratings If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. Maximum Input Voltage Temperature Range -40C TJ 125C LM2941T Input Voltage (Survival Voltage, 100ms) LM2941T, LM2941S, LM2941LD 60V LM2941CT, LM2941CS 45V Internal Power Dissipation (Note 4) Internally Limited Maximum Junction Temperature 150C Storage Temperature Range 26V 0C TJ 125C LM2941CT -40C TJ 125C LM2941S 0C TJ 125C LM2941CS -40C TJ 125C LM2941LD -65C TJ +150C Soldering Temperature (Note 9) TO-220 (T), Wave TO-263 (S) LLP-8 (LD) ESD Rating (Note 2) 260C, 10s 235C, 30s 235C, 30s 2 kV Electrical Characteristics--LM2941T, LM2941S, LM2941LD 5V VO 20V, VIN = VO + 5V, CO = 22F, unless otherwise specified. Specifications in standard typeface apply for TJ = 25C, while those in boldface type apply over the full Operating Temperature Range. Parameter Reference Voltage Line Regulation Conditions Typ 5mA IO 1A (Note 7) 1.275 VO + 2V VIN 26V, IO = 5mA LM2941T LM2941S LM2941LD Limit Units (Limits) 1.237/1.211 V(min) 1.313/1.339 V(max) 4 10/10 mV/V(max) 10/10 mV/V(max) Load Regulation 50mA IO 1A 7 Output Impedance 100 mADC and 20 mArms fO = 120Hz 7 VO + 2V VIN < 26V, IO = 5mA 10 15/20 mA(max) VIN = VO + 5V, IO = 1A 30 45/60 mA(max) Quiescent Current RMS Output Noise, % of VOUT 10Hz-100kHz IO = 5mA 0.003 Ripple Rejection fO = 120Hz, 1 Vrms, IL = 100mA 0.005 Long Term Stability m/V % 0.02/0.04 0.4 %/V(max) %/1000 Hr IO = 1A 0.5 0.8/1.0 V(max) IO = 100mA 110 200/200 mV(max) Short Circuit Current VIN Max = 26V (Note 8) 1.9 1.6 A(min) Maximum Line Transient VO Max 1V Above Nominal VO 75 60/60 V(min) 31 26/26 VDC Dropout Voltage RO = 100, t 100ms Maximum Operational Input Voltage Reverse Polarity DC Input Voltage RO = 100, VO -0.6V -30 -15/-15 V(min) Reverse Polarity Transient Input Voltage t 100ms, RO = 100 -75 -50/-50 V(min) ON/OFF Threshold Voltage ON IO 1A 1.30 0.80/0.80 V(max) ON/OFF Threshold Voltage OFF IO 1A 1.30 2.00/2.00 V(min) ON/OFF Threshold Current VON/OFF = 2.0V, IO 1A 50 100/300 A(max) www.ti.com 2 5V VO 20V, VIN = VO + 5V, CO = 22F, unless otherwise specified. Specifications in standard typeface apply for TJ = 25C, while those in boldface type apply over the full Operating Temperature Range. Parameter Conditions Typ Units (Limits) 1.237/1.211 V(min) 1.313/1.339 V(max) 4 10 mV/V(max) 50mA IO 1A 7 10 mV/V(max) 100 mADC and 20 mArms fO = 120Hz 7 VO + 2V VIN < 26V, IO = 5mA 10 15 mA(max) VIN = VO + 5V, IO = 1A 30 45/60 mA(max) Reference Voltage 5mA IO 1A (Note 7) Line Regulation VO + 2V VIN 26V, IO = 5mA Load Regulation Output Impedance Quiescent Current Limit (Note 6) 1.275 RMS Output Noise, % of VOUT 10Hz-100kHz IO = 5mA 0.003 Ripple Rejection fO = 120Hz, 1 Vrms, IL = 100mA 0.005 Long Term Stability m/V % 0.02 0.4 %/V(max) %/1000 Hr IO = 1A 0.5 0.8/1.0 V(max) IO = 100mA 110 200/200 mV(max) Short Circuit Current VIN Max = 26V (Note 8) 1.9 1.6 A(min) Maximum Line Transient VO Max 1V Above Nominal VO 55 45 V(min) 31 26 VDC Dropout Voltage RO = 100, T 100ms Maximum Operational Input Voltage Reverse Polarity DC Input Voltage RO = 100, VO -0.6V -30 -15 V(min) Reverse Polarity Transient Input Voltage T 100ms, RO = 100 -55 -45 V(min) ON/OFF Threshold Voltage ON IO 1A 1.30 0.80 V(max) ON/OFF Threshold Voltage OFF IO 1A 1.30 2.00 V(min) ON/OFF Threshold Current VON/OFF = 2.0V, IO 1A 50 100 A(max) Thermal Performance Thermal Resistance Junction-to-Case, JC Thermal Resistance Junction-to-Ambient, JA (Note 4) 5-Lead TO-220 1 C/W 5-Lead TO-263 1 C/W 8-Lead LLP 5.3 C/W 5-Lead TO-220 53 C/W 5-Lead TO-263 (See TO-263 MOUNTING) 73 C/W 8-Lead LLP (See LLP MOUNTING) 35 C/W Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The Human Body Model (HBM) is a 100 pF capacitor discharged through a 1.5k resistor into each pin. Test method is per JESD22-A114. Note 3: A military RETS specification available upon request. For more information about military-aerospace products, see the Mil-Aero web page at http:// www.national.com/appinfo/milaero/index.html. Note 4: The maximum power dissipation is a function of TJ(max), JA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max) - TA)/JA. If this dissipation is exceeded, the die temperature will rise above 150C and the LM2941 will go into thermal shutdown. If the TO-263 package is used, the thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package: Using 0.5 square inches of copper area, JA is 50C/W; with 1 square inch of copper area, JA is 37C/W; and with 1.6 or more square inches of copper area, JA is 32C/W. Thermal performance for the LLP package was obtained using a JESD51-7 board with six vias, using no airflow and an ambient temperature of 22C. The value JA for the LLP package 3 www.ti.com LM2941/LM2941C Electrical Characteristics--LM2941CT, LM2941CS LM2941/LM2941C is specifically dependent on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the LLP package, refer to Application Note AN-1187. It is recommended that 6 vias be placed under the center pad to improve thermal performance. Note 5: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (boldface type). All limits are used to calculate Outgoing Quality Level, and are 100% production tested. Note 6: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (boldface type). All room temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. Note 7: The output voltage range is 5V to 20V and is determined by the two external resistors, R1 and R2. See Typical Application Circuit. Note 8: Output current capability will decrease with increasing temperature, but will not go below 1A at the maximum specified temperatures. Note 9: Refer to JEDEC J-STD-020C for surface mount device (SMD) package reflow profiles and conditions. Unless otherwise stated, the temperature and time are for Sn-Pb (STD) only. Typical Performance Characteristics Dropout Voltage Dropout Voltage vs. Temperature 882312 882311 Output Voltage Quiescent Current vs. Temperature 882313 www.ti.com 882314 4 LM2941/LM2941C Quiescent Current Quiescent Current 882315 882316 Line Transient Response Load Transient Response 882318 882317 Ripple Rejection Output Impedance 882319 882320 5 www.ti.com LM2941/LM2941C Low Voltage Behavior Low Voltage Behavior 882321 882322 Output Capacitor ESR Output at Voltage Extremes 882324 882323 Output at Voltage Extremes Peak Output Current 882325 www.ti.com 882326 6 LM2941/LM2941C Maximum Power Dissipation (TO-220) Maximum Power Dissipation (TO-263) 882329 882327 Definition of Terms Dropout Voltage: The input-voltage differential at which the circuit ceases to regulate against further reduction in input voltage. Measured when the output voltage has dropped 100mV from the nominal value obtained at (VOUT + 5V) input, dropout voltage is dependent upon load current and junction temperature. Input Voltage: The DC voltage applied to the input terminals with respect to ground. Input-Output Differential: The voltage difference between the unregulated input voltage and the regulated output voltage for which the regulator will operate. Line Regulation: The change in output voltage for a change in the input voltage. The measurement is made under conditions of low dissipation or by using pulse techniques such that the average chip temperature is not significantly affected. Load Regulation: The change in output voltage for a change in load current at constant chip temperature. Long Term Stability: Output voltage stability under accelerated life-test conditions after 1000 hours with maximum rated voltage and junction temperature. Output Noise Voltage: The rms AC voltage at the output, with constant load and no input ripple, measured over a specified frequency range. Quiescent Current: That part of the positive input current that does not contribute to the positive load current. The regulator ground lead current. Ripple Rejection: The ratio of the peak-to-peak input ripple voltage to the peak-to-peak output ripple voltage. Temperature Stability of VO: The percentage change in output voltage for a thermal variation from room temperature to either temperature extreme. 7 www.ti.com LM2941/LM2941C Application Hints or recommended, as this may shorten the lifetime of the device. OUTPUT CAPACITOR A Tantalum capacitor with a minimum capacitance value of 22 F, and ESR in the range of 0.01 to 5, is required at the output pin for loop stability. It must be located less than 1 cm from the device. There is no limitation on any additional capacitance. Alternately, a high quality X5R/X7R 22 F ceramic capacitor may be used for the output capacitor only if an appropriate value of series resistance is added to simulate the ESR requirement. The ceramic capacitor selection must include an appropriate voltage de-rating of the capacitance value due to the applied output voltage. The series resistor (for ESR simulation) should be in the range of 0.1 to 1.0. POWER DISSIPATION Consideration should be given to the maximum power dissipation (PD(MAX)) which is limited by the maximum operating junction temperature (TJ(MAX)) of 125C, the maximum operating ambient temperature (TA(MAX)) of the application, and the thermal resistance (JA) of the package. Under all possible conditions, the junction temperature (TJ) must be within the range specified in the Operating Ratings. The total power dissipation of the device is given by: PD = ( (VIN - VOUT) x IOUT) + (VIN x IGND) where I GND is the operating ground pin current of the device (specified under Electrical Characteristics). The maximum allowable junction temperature rise (TJ) depends on the maximum expected ambient temperature (TA(MAX)) of the application, and the maximum allowable junction temperature (TJ(MAX)): SETTING THE OUTPUT VOLTAGE The output voltage range is 5V to 20V and is set by the two external resistors, R1 and R2. See the Typical Applications. The output voltage is given by the formula: TJ = TJ(MAX) - TA(MAX) VOUT = VREF x ((R1+R2) / R1) The maximum allowable value for junction to ambient Thermal Resistance, JA, required to keep the junction temperature, TJ, from exceeding maximum allowed can be calculated using the formula: where VREF is typically 1.275V. Using 1.00 k for R1 will ensure that the bias current error of the adjust pin will be negligible. Using a R1 value higher than 10 k may cause the output voltage to shift across temperature due to variations in the adjust pin bias current. Calculating the upper resistor (R2) value of the pair when the lower resistor (R1) value is known is accomplished with the following formula: JA = TJ / PD(MAX) The maximum allowable power dissipation, PD(MAX), required allowed for a specific ambient temperature can be calculated using the formula: R2 = R1 x ((VOUT / VREF) - 1) PD(MAX) = TJ / JA The resistors used for R1 and R2 should be high quality, tight tolerance, and with matching temperature coefficients. It is important to remember that, although the value of VREF is guaranteed, the final value of VOUT is not. The use of low quality resistors for R1 and R2 can easily produce a VOUT value that is unacceptable. Additional information for thermal performance of surface mount packages can be found in AN-1520: A Guide to Board Layout for Best Thermal Resistance for Exposed Packages, AN-1187: Leadless Leadframe Package (LLP), and AN-2020: Thermal Design By Insight, Not Hindsight . TO-263 MOUNTING The thermal dissipation of the TO-263 package is directly related to the printed circuit board construction and the amount of additional copper area connected to the TAB. The TAB on the bottom of the TO-263 package is connected to the die substrate via a conductive die attach adhesive, and to device pin 3. As such, it is strongly recommend that the TAB area be connected to copper area directly under the TAB that is extended into the ground plane via multiple thermal vias. Alternately, but not recommended, the TAB may be left floating (i.e. no direct electrical connection). The TAB must not be connected to any potential other than ground. For the LM2941S in the TS5B TO-263 package, the junctionto-case thermal rating, JC, is 1C/W, where the CASE is defined as the bottom of the package at the center of the TAB area. The junction-to-ambient thermal performance for the LM2941S in the TO-263 package, using the JEDEC JESD51 standards is summarized in the following table: ON/OFF The ON/OFF pin has no internal pull-up or pull-down to establish a default condition and, as a result, this pin must be terminated externally, either actively or passively. The ON/OFF pin requires a low level to enable the output, and a high level to disable the output. To ensure reliable operation, the ON/OFF pin voltage must rise above the maximum ON/ OFF(OFF) voltage threshold (2.00V) to disable the output, and must fall below the minimum ON/OFF(ON) voltage threshold (0.80V) to enable the output. If the ON/OFF function is not needed this pin can be connected directly to Ground. If the ON/OFF pin is being pulled to a high state through a series resistor, an allowance must be made for the ON/OFF pin current that will cause a voltage drop across the pull-up resistor. THERMAL OVERLOAD PROTECTION The LM2941 incorporates a linear form of thermal protection that limits the junction temperature (TJ) to typically 155C. Should the LM2941 see a fault condition that results in excessive power dissipation and the junction temperature approaches 155C, the device will respond by reducing the output current (which reduces the power dissipation) to hold the junction temperature at 155C. Thermal Overload protection is not a guaranteed operating condition. Operating at, or near to, the Thermal Overload condition for any extended period of time is not encouraged, www.ti.com 8 Thermal Vias JC JA JEDEC 2-Layer JESD 51-3 None 1C/W 73C/W 1 1C/W 35C/W 2 1C/W 30C/W 4 1C/W 26C/W 8 1C/W 24C/W JEDEC 4-Layer JESD 51-7 JA = 35C/W 5 JA = 30C/W JA = 26C/W 4 JA = 24C/W 3 Board Type Thermal Vias JC JA JEDEC 2-Layer JESD 51-3 None 5.3C/W 181C/W 1 5.3C/W 58C/W 2 5.3C/W 49C/W 4 5.3C/W 40C/W 6 5.3C/W 35C/W JEDEC 4-Layer JESD 51-7 2 1 LM2941S (TO-263) 0 0 20 40 60 80 AMBIENT TEMPERATURE (C) 6 100 POWER DISSIPATION (W) POWER DISSIPATION (W) 6 recommend that the DAP area be connected copper area directly under the DAP that is extended into the ground plane via multiple thermal vias. Alternately, but not recommended, the DAP area may be left floating (i.e. no direct electrical connection). The DAP area must not be connected to any potential other than ground. For the LM2941LD in the LDC08A 8-Lead LLP package, the junction-to-case thermal rating, JC, is 5.3C/W, where the CASE is defined as the bottom of the package at the center of the DAP area. The junction-to-ambient thermal performance for the LM2941LD in the LDC08A 8-Lead LLP package, using the JEDEC JESD51 standards is summarized in the following table: 882334 FIGURE 1. PD(MAX) vs TA for LM2941S (TO-263) LLP MOUNTING The LDC08A (Pullback) 8-Lead LLP package requires specific mounting techniques which are detailed in Application Note # 1187. Referring to the section PCB Design Recommendations in AN-1187 (Page 5), it should be noted that the pad style which should be used with the LLP package is the NSMD (non-solder mask defined) type. The thermal dissipation of the LLP package is directly related to the printed circuit board construction and the amount of additional copper area connected to the DAP. The DAP (exposed pad) on the bottom of the LLP package is connected to the die substrate via a conductive die attach adhesive, and to device pin 2 and pin 7. As such, it is strongly JA = 58C/W 5 JA = 49C/W 4 JA = 40C/W JA = 35C/W 3 2 1 LM2941LD (LLP) 0 0 20 40 60 80 AMBIENT TEMPERATURE (C) 100 882335 FIGURE 2. PD(MAX) vs TA for LM2941LD (LLP) 9 www.ti.com LM2941/LM2941C Board Type LM2941/LM2941C Typical Applications 5V to 20V Adjustable Regulator 882303 Note: Using 1k for R1 will ensure that the bias current error from the adjust pin will be negligible. Do not bypass R1 or R2. This will lead to instabilities. * Required if regulator is located far from power supply filter. ** COUT must be at least 22F to maintain stability. May be increased without bound to maintain regulation during transients. Locate as close as possible to the regulator. This capacitor must be rated over the same operating temperature range as the regulator and the ESR is critical; see curve. 1A Switch 882306 *** To assure shutdown, select Resistor R3 to guarantee at least 300A of pull-up current when S1 is open. (Assume 2V at the ON/OFF pin.) www.ti.com 10 LM2941/LM2941C Equivalent Schematic Diagram 882301 11 www.ti.com LM2941/LM2941C Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM2941T or LM2941CT NS Package Number T05A TO-263 5-Lead Plastic Surface Mount Package Order Number LM2941S, LM2941SX, LM2941CS or LM2941CSX NS Package Number TS5B www.ti.com 12 LM2941/LM2941C 8-Lead LLP Surface Mount Package Order Number LM2941LD, LM2941LDX NS Package Number LDC08A 13 www.ti.com LM2941/LM2941C 1A Low Dropout Adjustable Regulator Notes www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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