SM74503 SM74503 800mA Low-Dropout Linear Regulator Literature Number: SNVS722 SM74503 800mA Low-Dropout Linear Regulator General Description Features The SM74503 is a series of low dropout voltage regulators with a dropout of 1.2V at 800mA of load current. It has the same pin-out as National Semiconductor's industry standard LM317. The SM74503 is available in two fixed voltages, 3.3V and 5V. The SM74503 offers current limiting and thermal shutdown. Its circuit includes a zener trimmed bandgap reference to assure output voltage accuracy to within ±1%. The SM74503 series is available in SOT-223 and TO-252 DPAK packages. A minimum of 10µF tantalum capacitor is required at the output to improve the transient response and stability. ■ ■ ■ ■ ■ ■ ■ ■ Renewable Energy Grade Available in 3.3V and 5V Versions Space Saving SOT-223 Package Current Limiting and Thermal Protection Output Current 800mA Line Regulation 0.2% (Max) Load Regulation 0.4% (Max) Temperature Range −40°C to 125°C Applications ■ ■ ■ ■ ■ Photovoltaic Electronics Post Regulator for Switching DC/DC Converter High Efficiency Linear Regulators Battery Charger Battery Powered Instrumentation Typical Application Fixed Output Regulator 30160628 © 2011 Texas Instruments Incorporated 301606 www.ti.com SM74503 800mA Low-Dropout Linear Regulator November 30, 2011 SM74503 Ordering Information Package 4-lead SOT-223 3-lead TO-252 www.ti.com Part Number Packaging Marking Transport Media SM74503MP-3.3 S503 1000 UnitsTape and Reel SM74503MPE-3.3 S503 250 UnitsTape and Reel SM74503MPX-3.3 S503 2000 UnitsTape and Reel SM74503MP-5.0 S503 1000 UnitsTape and Reel SM74503MPE-5.0 S503 250 UnitsTape and Reel SM74503MPX-5.0 S503 2000 UnitsTape and Reel SM74503TD-3.3 S74503-3.3 75 Unit Raill SM74503TDE-3.3 S74503-3.3 250 UnitsTape and Reel SM74503TDX-3.3 S74503-3.3 2500 UnitsTape and Reel SM74503TD-5.0 S74503-5.0 75 Unit Rail SM74503TDE-5.0 S74503-5.0 250 UnitsTape and Reel SM74503TDX-5.0 S74503-5.0 2500 UnitsTape and Reel 2 NSC Drawing MP04A TD03B SM74503 Block Diagram 30160601 TO-252 Connection Diagrams SOT-223 30160638 Top View 30160604 Top View 3 www.ti.com SM74503 Lead Temperature SOT-223 (MP) Package ESD Tolerance (Note 3) Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. Maximum Input Voltage (VIN to GND) Power Dissipation (Note 2) Junction Temperature (TJ) (Note 2) Storage Temperature Range 260°C, 4 sec 2000V Operating Ratings 20V Internally Limited (Note 1) Input Voltage (VIN to GND) 15V Junction Temperature Range (TJ)(Note 2) SM74503 −40°C to 125°C 150°C -65°C to 150°C SM74503 Electrical Characteristics Typicals and limits appearing in normal type apply for TJ = 25°C. Limits appearing in Boldface type apply over the entire junction temperature range for operation, −40°C to 125°C. Symbol VOUT Min (Note 5) Typ (Note 4) Max (Note 5) Units SM74503-3.3 IOUT = 10mA, VIN = 5V, TJ = 25°C 3.267 3.168 3.300 3.300 3.333 3.432 V V SM74503-5.0 IOUT = 10mA, VIN = 7V, TJ = 25°C 4.950 4.800 5.000 5.000 5.050 5.200 V V 1 10 mV 1 15 mV 1 15 mV 1 20 mV IOUT = 100mA 1.10 1.30 V IOUT = 500mA 1.15 1.35 V IOUT = 800mA 1.20 1.40 V 1200 1500 mA 5 15 mA 5 15 mA 0.01 0.1 %/W Parameter Output Voltage Conditions 0 ≤ IOUT ≤ 800mA, 4.75V ≤ VIN ≤ 10V 0 ≤ IOUT ≤ 800mA, 6.5V ≤ VIN ≤ 12V ΔVOUT Line Regulation (Note 6) SM74503-3.3 IOUT = 0mA, 4.75V ≤ VIN ≤ 15V SM74503-5.0 IOUT = 0mA, 6.5V ≤ VIN ≤ 15V ΔVOUT Load Regulation (Note 6) SM74503-3.3 VIN = 4.75V, 0 ≤ IOUT ≤ 800mA SM74503-5.0 VIN = 6.5V, 0 ≤ IOUT ≤ 800mA VIN-V OUT ILIMIT Dropout Voltage (Note 7) Current Limit VIN-VOUT = 5V, TJ = 25°C Quiescent Current SM74503-3.3 800 VIN ≤ 15V SM74503-5.0 VIN ≤ 15V Thermal Regulation TA = 25°C, 30ms Pulse Ripple Regulation fRIPPLE =1 20Hz, VIN-VOUT = 3V VRIPPLE = 1VPP Temperature Stability 60 75 dB 0.5 % 0.3 % % Long Term Stability TA = 125°C, 1000Hrs RMS Output Noise (% of VOUT), 10Hz ≤ f ≤10kHz 0.003 Thermal Resistance Junction-to-Case 4-Lead SOT-223 15.0 °C/W 3-Lead TO-252 10 °C/W Thermal Resistance Junction-to-Ambient No air flow) 4-Lead SOT-223 (No heat sink) 136 °C/W 3-Lead TO-252 (No heat sink)(Note 8) 92 °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 specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics. Note 2: The maximum power dissipation is a function of TJ(max) , θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max)–TA)/θJA. All numbers apply for packages soldered directly into a PC board. Note 3: For testing purposes, ESD was applied using human body model, 1.5kΩ in series with 100pF. www.ti.com 4 Note 5: All limits are guaranteed by testing or statistical analysis. Note 6: Load and line regulation are measured at constant junction room temperature. Note 7: The dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage. It is measured when the output voltage has dropped 100mV from the nominal value obtained at VIN = VOUT +1.5V. Note 8: Minimum pad size of 0.038in2 Typical Performance Characteristics Dropout Voltage (VIN-V OUT) Short-Circuit Current 30160623 30160622 Load Regulation Temperature Stability 30160643 30160625 5 www.ti.com SM74503 Note 4: Typical Values represent the most likely parametric norm. SM74503 SM74503-5.0 Load Transient Response SM74503-5.0 Line Transient Response 30160609 www.ti.com 30160611 6 SM74503 Application Note 1.0 EXTERNAL CAPACITORS/STABILITY 1.1 Input Bypass Capacitor An input capacitor is recommended. A 10µF tantalum on the input is a suitable input bypassing for almost all applications. 1.2 Output Capacitor The output capacitor is critical in maintaining regulator stability, and must meet the required conditions for both minimum amount of capacitance and ESR (Equivalent Series Resistance). The minimum output capacitance required by the SM74503 is 10µF, if a tantalum capacitor is used. Any increase of the output capacitance will merely improve the loop stability and transient response. The ESR of the output capacitor should range between 0.3Ω - 22Ω. 30160615 FIGURE 2. Regulator with Protection Diode 2.0 LOAD REGULATION The SM74503 regulates the voltage that appears between its output and ground pins. In some cases, line resistances can introduce errors to the voltage across the load. To obtain the best load regulation, a few precautions are needed. Figure 1, shows a typical application using a fixed output regulator. The Rt1 and Rt2 are the line resistances. It is obvious that the VLOAD is less than the VOUT by the sum of the voltage drops along the line resistances. In this case, the load regulation seen at the RLOAD would be degraded from the data sheet specification. To improve this, the load should be tied directly to the output terminal on the positive side and directly tied to the ground terminal on the negative side. 4.0 HEATSINK REQUIREMENTS When an integrated circuit operates with an appreciable current, its junction temperature is elevated. It is important to quantify its thermal limits in order to achieve acceptable performance and reliability. This limit is determined by summing the individual parts consisting of a series of temperature rises from the semiconductor junction to the operating environment. A one-dimensional steady-state model of conduction heat transfer is demonstrated in Figure 3. The heat generated at the device junction flows through the die to the die attach pad, through the lead frame to the surrounding case material, to the printed circuit board, and eventually to the ambient environment. Below is a list of variables that may affect the thermal resistance and in turn the need for a heatsink. RθJC (Component Variables) Leadframe Size & Material No. of Conduction Pins Die Size Die Attach Material Molding Compound Size and Material 30160618 FIGURE 1. Typical Application using Fixed Output Regulator Rθ CA (Application Variables) Mounting Pad Size, Material, & Location Placement of Mounting Pad PCB Size & Material Traces Length & Width Adjacent Heat Sources Volume of Air Ambient Temperatue Shape of Mounting Pad 3.0 PROTECTION DIODES Under normal operation, the SM74503 regulators do not need any protection diode. When a output capacitor is connected to a regulator and the input is shorted to ground, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage of the regulator, and rate of decrease of VIN. In the SM74503 regulators, the internal diode between the output and input pins can withstand microsecond surge currents of 10A to 20A. With an extremely large output capacitor (≥1000 µF), and with input instantaneously shorted to ground, the regulator could be damaged. In this case, an external diode is recommended between the output and input pins to protect the regulator, as shown in Figure 2. 30160637 FIGURE 3. Cross-sectional view of Integrated Circuit Mounted on a printed circuit board. Note that the case temperature is measured at the point where the leads contact with the mounting pad surface The SM74503 regulators have internal thermal shutdown to protect the device from over-heating. Under all possible operating conditions, the junction temperature of the SM74503 7 www.ti.com SM74503 must be within the range of –40°C to 125°C. A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the application. To determine if a heatsink is needed, the power dissipated by the regulator, PD , must be calculated: IIN = IL + IG PD = (VIN-VOUT)I L + VINIG Figure 4 shows the voltages and currents which are present in the circuit. TR(max) = TJ(max)-TA(max) where TJ(max) is the maximum allowable junction temperature (125°C), and TA(max) is the maximum ambient temperature which will be encountered in the application. Using the calculated values for TR(max) and PD, the maximum allowable value for the junction-to-ambient thermal resistance (θJA) can be calculated: θJA = TR(max)/PD If the maximum allowable value for θJA is found to be ≥136° C/W for SOT-223 package or ≥92°C/W for TO-252 package, no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. If the calculated value for θJA falls below these limits, a heatsink is required. As a design aid, Table 1 shows the value of the θJA of SOT-223 and TO-252 for different heatsink area. The copper patterns that we used to measure these θJAs are shown at the end of the Application Notes Section. Figure 5 and Figure 6 reflects the same test results as what are in the Table 1 Figure 7 and Figure 8 shows the maximum allowable power dissipation vs. ambient temperature for the SOT-223 and TO-252 device. Figure 9 and Figure 10 shows the maximum allowable power dissipation vs. copper area (in2) for the SOT-223 and TO-252 devices. Please see AN1028 for power enhancement techniques to be used with SOT-223 and TO-252 packages. 30160616 FIGURE 4. Power Dissipation Diagram The next parameter which must be calculated is the maximum allowable temperature rise, TR(max): TABLE 1. θJA Different Heatsink Area Layout Copper Area Top Side (in2)* Thermal Resistance Bottom Side (θJA,°C/W) SOT-223 (θJA,°C/W) TO-252 1 0.0123 0 136 103 2 0.066 0 123 87 3 0.3 0 84 60 4 0.53 0 75 54 5 0.76 0 69 52 6 1 0 66 47 7 0 0.2 115 84 8 0 0.4 98 70 9 0 0.6 89 63 10 0 0.8 82 57 11 0 1 79 57 12 0.066 0.066 125 89 13 0.175 0.175 93 72 14 0.284 0.284 83 61 15 0.392 0.392 75 55 16 0.5 0.5 70 53 *Tab of device attached to topside copper www.ti.com (in2) 8 SM74503 30160636 30160613 FIGURE 8. Maximum Allowable Power Dissipation vs. Ambient Temperature for TO-252 FIGURE 5. θJA vs. 1oz Copper Area for SOT-223 30160634 30160614 FIGURE 6. θJA vs. 2oz Copper Area for TO-252 FIGURE 9. Maximum Allowable Power Dissipation vs. 1oz Copper Area for SOT-223 30160612 30160635 FIGURE 7. Maximum Allowable Power Dissipation vs. Ambient Temperature for SOT-223 FIGURE 10. Maximum Allowable Power Dissipation vs. 2oz Copper Area for TO-252 9 www.ti.com SM74503 30160641 FIGURE 11. Top View of the Thermal Test Pattern in Actual Scale www.ti.com 10 SM74503 30160642 FIGURE 12. Bottom View of the Thermal Test Pattern in Actual Scale 11 www.ti.com SM74503 Typical Application Circuits 30160631 Regulator with Reference 30160630 Adjusting Output of Fixed Regulators 30160632 Battery Backed-Up Regulated Supply 30160633 Low Dropout Negative Supply www.ti.com 12 SM74503 Physical Dimensions inches (millimeters) unless otherwise noted 4-Lead SOT-223 NS Package Number MP04A 3-Lead TO-252 NS Package Number TD03B 13 www.ti.com SM74503 800mA Low-Dropout Linear Regulator Notes TI/NATIONAL INTERIM IMPORTANT NOTICE Texas Instruments has purchased National Semiconductor. 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