LM340/LM78XX Series 3-Terminal Positive Regulators General Description The LM140/LM340A/LM340/LM78XXC monolithic 3-terminal positive voltage regulators employ internal current-limiting, thermal shutdown and safe-area compensation, making them essentially indestructible. If adequate heat sinking is provided, they can deliver over 1.0A output current. They are intended as fixed voltage regulators in a wide range of applications including local (on-card) regulation for elimination of noise and distribution problems associated with single-point regulation. In addition to use as fixed voltage regulators, these devices can be used with external components to obtain adjustable output voltages and currents. Considerable effort was expended to make the entire series of regulators easy to use and minimize the number of external components. It is not necessary to bypass the output, although this does improve transient response. Input bypassing is needed only if the regulator is located far from the filter capacitor of the power supply. The 5V, 12V, and 15V regulator options are available in the steel TO-3 power package. The LM340A/LM340/LM78XXC series is available in the TO-220 plastic power package, and the LM340-5.0 is available in the SOT-223 package, as well as the LM340-5.0 and LM340-12 in the surface-mount TO263 package. Features n Complete specifications at 1A load n Output voltage tolerances of ± 2% at Tj = 25˚C and ± 4% over the temperature range (LM340A) n Line regulation of 0.01% of VOUT/V of ∆VIN at 1A load (LM340A) n Load regulation of 0.3% of VOUT/A (LM340A) n Internal thermal overload protection n Internal short-circuit current limit n Output transistor safe area protection n P+ Product Enhancement tested Typical Applications Fixed Output Regulator Adjustable Output Regulator 00778102 00778101 *Required if the regulator is located far from the power supply filter. VOUT = 5V + (5V/R1 + IQ) R2 5V/R1 > 3 IQ, load regulation (Lr) ≈ [(R1 + R2)/R1] (Lr of LM340-5). **Although no output capacitor is needed for stability, it does help transient response. (If needed, use 0.1 µF, ceramic disc). Comparison between SOT-223 and D-Pak (TO-252) Packages Current Regulator 00778103 00778138 Scale 1:1 ∆IQ = 1.3 mA over line and load changes. © 2004 National Semiconductor Corporation DS007781 www.national.com LM340/LM78XX Series 3-Terminal Positive Regulators November 2004 LM340/LM78XX Ordering Information Package Temperature Range Part Number Packaging Marking Transport Media NSC Drawing 3-Lead TO-3 -55˚C to +125˚C LM140K-5.0 LM140K 5.0P+ 50 Per Tray K02A LM140K-12 LM140K 12P+ 50 Per Tray LM140K-15 LM140K 15P+ 50 Per Tray LM340K-5.0 LM340K 5.0 7805P+ 50 Per Tray LM340K-12 LM340K 12 7812P+ 50 Per Tray LM340K-15 LM340K 15 7815P+ 50 Per Tray LM340AT-5.0 LM340AT 5.0 P+ 45 Units/Rail LM340T-5.0 LM340T5 7805 P+ 45 Units/Rail LM340T-12 LM340T12 7812 P+ 45 Units/Rail LM340T-15 LM340T15 7815 P+ 45 Units/Rail LM7808CT LM7808CT 45 Units/Rail 0˚C to +125˚C 3-lead TO-220 3-Lead TO-263 0˚C to +125˚C 0˚C to +125˚C LM340S-5.0 LM340S-12 LM340ASX-5.0 4-Lead SOT-223 0˚C to +125˚C Unpackaged Die −55˚C to 125˚C 0˚C to +125˚C 45 Units/Rail 500 Units Tape and Reel LM340AS-5.0 P+ LM340MP-5.0 N00A LM340MPX-5.0 TS3B 500 Units Tape and Reel LM340S-12 P+ LM340SX-12 LM340AS-5.0 45 Units/Rail LM340S-5.0 P+ LM340SX-5.0 T03B 45 Units/Rail 500 Units Tape and Reel 1k Units Tape and Reel LM140KG-5 MD8 Waffle Pack or Gel Pack DL069089 LM140KG-12 MD8 Waffle Pack or Gel Pack DL059093 LM140KG-15 MD8 Waffle Pack or Gel Pack DL059093 LM340-5.0 MDA Waffle Pack or Gel Pack DI074056 LM7808C MDC Waffle Pack or Gel Pack DI074056 Connection Diagrams TO-3 Metal Can Package (K) TO-220 Power Package (T) 00778112 00778111 Bottom View See Package Number K02A Top View See Package Number T03B TO-263 Surface-Mount Package (S) 3-Lead SOT-223 00778120 00778143 Top View See Package Number TS3B www.national.com MP04A 2k Units Tape and Reel Top View See Package Number MP04A 2 TO-220 Package (T), TO-263 Package (S) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Susceptibility (Note 3) (Note 5) DC Input Voltage Temperature Range (TA) (Note 2) Internally Limited Maximum Junction Temperature LM140 150˚C Storage Temperature Range −65˚C to +150˚C Lead Temperature (Soldering, 10 sec.) TO-3 Package (K) 2 kV Operating Conditions (Note 1) 35V Internal Power Dissipation (Note 2) 230˚C −55˚C to +125˚C LM340A, LM340 0˚C to +125˚C LM7808C 0˚C to +125˚C 300˚C LM340A Electrical Characteristics IOUT = 1A, 0˚C ≤ TJ ≤ + 125˚C (LM340A) unless otherwise specified (Note 4) Symbol Output Voltage 5V 12V 15V Input Voltage (unless otherwise noted) 10V 19V 23V Parameter VO ∆VO Output Voltage Line Regulation Conditions Min Typ Max TJ = 25˚C 4.9 PD ≤ 15W, 5 mA ≤ IO ≤ 1A 4.8 VMIN ≤ VIN ≤ VMAX (7.5 ≤ VIN ≤ 20) IO = 500 mA ∆VIN ∆VIN 11.75 5.2 11.5 Min 12 12.25 14.7 12.5 (14.8 ≤ VIN ≤ 27) Units Typ Max 15 14.4 15.3 V (17.9 ≤ VIN ≤ 30) V 18 22 (14.8 ≤ VIN ≤ 27) (17.9 ≤ VIN ≤ 30) 3 4 10 18 (14.5 ≤ VIN ≤ 27) V 15.6 10 (7.5 ≤ VIN ≤ 20) 4 22 (17.5 ≤ VIN ≤ 30) mV V mV V TJ = 25˚C 4 9 10 mV Over Temperature 12 30 30 mV (8 ≤ VIN ≤ 12) (16 ≤ VIN ≤ 22) (20 ≤ VIN ≤ 26) 10 12 ∆VIN Load Regulation 5.1 Typ Max (7.5 ≤ VIN ≤ 20) TJ = 25˚C ∆VO 5 Min TJ = 25˚C 5 mA ≤ IO ≤ 1.5A 250 mA ≤ IO ≤ 750 mA Over Temperature, 25 32 12 V 35 mV 15 19 21 mV 25 60 75 mV 6 6 6 mA 6.5 mA 5 mA ≤ IO ≤ 1A IQ Quiescent Current ∆IQ Quiescent Current TJ = 25˚C Over Temperature Change 6.5 5 mA ≤ IO ≤ 1A 0.5 0.5 mA TJ = 25˚C, IO = 1A 0.8 0.8 0.8 VMIN ≤ VIN ≤ VMAX (7.5 ≤ VIN ≤ 20) (14.8 ≤ VIN ≤ 27) (17.9 ≤ VIN ≤ 30) 0.8 0.8 0.8 (8 ≤ VIN ≤ 25) (15 ≤ VIN ≤ 30) (17.9 ≤ VIN ≤ 30) 40 75 IO = 500 mA VMIN ≤ VIN ≤ VMAX VN 6.5 0.5 mA V mA V Output Noise Voltage TA = 25˚C, 10 Hz ≤ f ≤ 100 kHz Ripple Rejection TJ = 25˚C, f = 120 Hz, IO = 1A 68 or f = 120 Hz, IO = 500 mA, 68 61 VMIN ≤ VIN ≤ VMAX (8 ≤ VIN ≤ 18) (15 ≤ VIN ≤ 25) Dropout Voltage TJ = 25˚C, IO = 1A 2.0 2.0 2.0 V Output Resistance f = 1 kHz 8 18 19 mΩ Short-Circuit Current TJ = 25˚C 2.1 1.5 1.2 A 80 61 72 90 60 µV 70 dB 60 dB Over Temperature, RO 3 (18.5 ≤ VIN ≤ 28.5) V www.national.com LM340/LM78XX Absolute Maximum Ratings (Note 1) LM340/LM78XX LM340A Electrical Characteristics (Continued) IOUT = 1A, 0˚C ≤ TJ ≤ + 125˚C (LM340A) unless otherwise specified (Note 4) Symbol Output Voltage 5V 12V 15V Input Voltage (unless otherwise noted) 10V 19V 23V Parameter VIN Conditions Min Typ Max Min Typ Max Min Units Typ Max Peak Output Current TJ = 25˚C 2.4 2.4 2.4 A Average TC of VO Min, TJ = 0˚C, IO = 5 mA −0.6 −1.5 −1.8 mV/˚C Input Voltage TJ = 25˚C Required to Maintain 7.5 14.5 17.5 V Line Regulation LM140 Electrical Characteristics (Note 4) −55˚C ≤ TJ ≤ +150˚C unless otherwise specified Symbol Output Voltage 5V 12V 15V Input Voltage (unless otherwise noted) 10V 19V 23V Parameter VO Output Voltage Conditions Min Typ Max TJ = 25˚C, 5 mA ≤ IO ≤ 1A 4.8 PD ≤ 15W, 5 mA ≤ IO ≤ 1A 4.75 VMIN ≤ VIN ≤ VMAX ∆VO Line Regulation IO = 500 mA 5 3 ∆VIN ∆VIN TJ = 25˚C ∆VIN TJ = 25˚C 12 5 mA ≤ IO ≤ 1.5A 12.5 14.4 15 12.6 14.25 (15.5 ≤ VIN ≤ 27) 4 120 (14.5 ≤ VIN ≤ 30) 4 V V 60 75 (16 ≤ VIN ≤ 22) (20 ≤ VIN ≤ 26) −55˚C ≤ TJ ≤ +150˚C, 50 12 120 V 150 mV (17.7 ≤ VIN ≤ 30) 25 10 V 150 mV (18.5 ≤ VIN ≤ 30) (8 ≤ VIN ≤ 12) 250 mA ≤ IP ≤ 750 mA V 150 mV (17.5 ≤ VIN ≤ 30) 120 (14.6 ≤ VIN ≤ 27) 15.6 15.75 (18.5 ≤ VIN ≤ 30) 120 (15 ≤ VIN ≤ 27) 50 (7.5 ≤ VIN ≤ 20) Units Typ Max Min Typ Max 50 −55˚C ≤ TJ ≤ +150˚C Load Regulation 50 (8 ≤ VIN ≤ 20) ∆VIN ∆VO 11.5 11.4 (7 ≤ VIN ≤ 25) −55˚C ≤ TJ ≤ +150˚C IO ≤ 1A 5.2 5.25 (8 ≤ VIN ≤ 20) TJ = 25˚C Min 12 V mV V 150 mV 25 60 75 mV 50 120 150 mV 5 mA ≤ IO ≤ 1A IQ ∆IQ Quiescent Current IO ≤ 1A TJ = 25˚C 6 6 6 mA −55˚C ≤ TJ ≤ +150˚C 7 7 7 mA Quiescent Current 5 mA ≤ IO ≤ 1A Change TJ = 25˚C, IO ≤ 1A 0.8 VMIN ≤ VIN ≤ VMAX (8 ≤ VIN ≤ 20) 0.5 IO = 500 mA, −55˚C ≤ TJ ≤ +150˚C VMIN ≤ VIN ≤ VMAX VN Output Noise Voltage www.national.com 0.5 TA = 25˚C, 10 Hz ≤ f ≤ 100 kHz 40 4 0.8 (15 ≤ VIN ≤ 27) 0.8 (8 ≤ VIN ≤ 25) 0.5 0.8 (18.5 ≤ VIN ≤ 30) 0.8 (15 ≤ VIN ≤ 30) 75 mA 0.8 mA V mA (18.5 ≤ VIN ≤ 30) V 90 µV (Note 4) (Continued) −55˚C ≤ TJ ≤ +150˚C unless otherwise specified Symbol Output Voltage 5V 12V 15V Input Voltage (unless otherwise noted) 10V 19V 23V Parameter Conditions Min Typ Max Min IO ≤ 1A, TJ = 25˚C 68 IO ≤ 500 mA, 68 61 VMIN ≤ VIN ≤ VMAX (8 ≤ VIN ≤ 18) (15 ≤ VIN ≤ 25) Ripple Rejection 80 61 Units Typ Max Min Typ Max 72 60 70 dB or f = 120 Hz 60 dB −55˚C ≤ TJ ≤+150˚C RO VIN (18.5 ≤ VIN ≤ 28.5) V Dropout Voltage TJ = 25˚C, IO = 1A 2.0 2.0 2.0 V Output Resistance f = 1 kHz 8 18 19 mΩ Short-Circuit Current TJ = 25˚C 2.1 1.5 1.2 A Peak Output Current TJ = 25˚C 2.4 2.4 2.4 A Average TC of VOUT 0˚C ≤ TJ ≤ +150˚C, IO = 5 mA −0.6 −1.5 −1.8 Input Voltage TJ = 25˚C, IO ≤ 1A Required to Maintain 7.5 14.6 mV/˚C 17.7 V Line Regulation LM340 Electrical Characteristics (Note 4) 0˚C ≤ TJ ≤ +125˚C unless otherwise specified Symbol Output Voltage 5V 12V 15V Input Voltage (unless otherwise noted) 10V 19V 23V Parameter VO ∆VO Output Voltage Line Regulation Conditions TJ = 25˚C, 5 mA ≤ IO ≤ 1A 4.8 PD ≤ 15W, 5 mA ≤ IO ≤ 1A 4.75 VMIN ≤ VIN ≤ VMAX (7.5 ≤ VIN ≤ 20) 3 IO = 500 mA TJ = 25˚C ∆VIN 5 5 mA ≤ IO ≤ 1A Change TJ = 25˚C, IO ≤ 1A (17.5 ≤ VIN ≤ 30) V 4 4 mV (14.5 ≤ VIN ≤ 30) 150 (17.5 ≤ VIN ≤ 30) 120 (14.6 ≤ VIN ≤ 27) 150 (17.7 ≤ VIN ≤ 30) V mV V mV V 25 60 75 (16 ≤ VIN ≤ 22) (20 ≤ VIN ≤ 26) V 10 12 12 50 120 mV 150 mV 25 60 75 mV 50 120 150 mV 8 8 8 mA 8.5 8.5 8.5 mA 0.5 0.5 1.0 5 120 (8 ≤ VIN ≤ 12) TJ = 25˚C Quiescent Current (14.5 ≤ VIN ≤ 27) 150 0˚C ≤ TJ ≤ +125˚C ∆IQ V V (18.5 ≤ VIN ≤ 30) 5 mA ≤ IO ≤ 1A, 0˚C ≤ TJ ≤ +125˚C IO ≤ 1A 15 120 250 mA ≤ IO ≤ 750 mA Quiescent Current 15.6 15.75 50 5 mA ≤ IO ≤ 1.5A 12.5 14.4 12.6 14.25 (15 ≤ VIN ≤ 27) (7.5 ≤ VIN ≤ 20) ∆VIN IQ 12 50 0˚C ≤ TJ ≤ +125˚C TJ = 25˚C 11.5 (8 ≤ VIN ≤ 20) TJ = 25˚C ∆VIN Load Regulation 50 (7 ≤ VIN ≤ 25) ∆VIN ∆VO 5.2 5.25 11.4 0˚C ≤ TJ ≤ +125˚C IO ≤ 1A Units Min Typ Max Min Typ Max Min Typ Max 0.5 1.0 mA 1.0 mA www.national.com LM340/LM78XX LM140 Electrical Characteristics LM340/LM78XX LM340 Electrical Characteristics (Note 4) (Continued) 0˚C ≤ TJ ≤ +125˚C unless otherwise specified Symbol Output Voltage 5V 12V 15V Input Voltage (unless otherwise noted) 10V 19V 23V Parameter Conditions VMIN ≤ VIN ≤ VMAX (7.5 ≤ VIN ≤ 20) IO ≤ 500 mA, 0˚C ≤ TJ ≤ +125˚C VMIN ≤ VIN ≤ VMAX VN Output Noise Voltage IO ≤ 1A, TJ = 25˚C 1.0 (17.9 ≤ VIN ≤ 30) 1.0 1.0 V mA (14.5 ≤ VIN ≤ 30) (17.5 ≤ VIN ≤ 30) V 40 75 90 µV 70 dB 62 or IO ≤ 500 mA, (14.8 ≤ VIN ≤ 27) (7 ≤ VIN ≤ 25) TA = 25˚C, 10 Hz ≤ f ≤ 100 kHz Ripple Rejection Units Min Typ Max Min Typ Max Min Typ Max 80 55 72 54 62 55 VMIN ≤ VIN ≤ VMAX (8 ≤ VIN ≤ 18) (15 ≤ VIN ≤ 25) (18.5 ≤ VIN ≤ 28.5) Dropout Voltage TJ = 25˚C, IO = 1A 2.0 2.0 2.0 V Output Resistance f = 1 kHz 8 18 19 mΩ Short-Circuit Current TJ = 25˚C 2.1 1.5 1.2 A Peak Output Current 2.4 2.4 2.4 A −0.6 −1.5 −1.8 f = 120 Hz 54 dB 0˚C ≤ TJ ≤ +125˚C RO TJ = 25˚C Average TC of VOUT 0˚C ≤ TJ ≤ +125˚C, IO = 5 mA VIN Input Voltage V mV/˚C TJ = 25˚C, IO ≤ 1A Required to Maintain 7.5 14.6 17.7 V Line Regulation Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Conditions are conditions under which the device functions but the specifications might not be guaranteed. For guaranteed specifications and test conditions see the Electrical Characteristics. Note 2: The maximum allowable power dissipation at any ambient temperature is a function of the maximum junction temperature for operation (TJMAX = 125˚C or 150˚C), the junction-to-ambient thermal resistance (θJA), and the ambient temperature (TA). PDMAX = (TJMAX − TA)/θJA. If this dissipation is exceeded, the die temperature will rise above TJMAX and the electrical specifications do not apply. If the die temperature rises above 150˚C, the device will go into thermal shutdown. For the TO-3 package (K, KC), the junction-to-ambient thermal resistance (θJA) is 39˚C/W. When using a heatsink, θJA is the sum of the 4˚C/W junction-to-case thermal resistance (θJC) of the TO-3 package and the case-to-ambient thermal resistance of the heatsink. For the TO-220 package (T), θJA is 54˚C/W and θJC is 4˚C/W. If SOT-223 is used, the junction-to-ambient thermal resistance is 174˚C/W and can be reduced by a heatsink (see Applications Hints on heatsinking). If the TO-263 package is used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the package: Using 0.5 square inches of copper area, θJA is 50˚C/W; with 1 square inch of copper area, θJAis 37˚C/W; and with 1.6 or more inches of copper area, θJA is 32˚C/W. Note 3: ESD rating is based on the human body model, 100 pF discharged through 1.5 kΩ. Note 4: All characteristics are measured with a 0.22 µF capacitor from input to ground and a 0.1 µF capacitor from output to ground. All characteristics except noise voltage and ripple rejection ratio are measured using pulse techniques (tw ≤ 10 ms, duty cycle ≤ 5%). Output voltage changes due to changes in internal temperature must be taken into account separately. Note 5: Military datasheets are available upon request. At the time of printing, the military datasheet specifications for the LM140K-5.0/883, LM140K-12/883, and LM140K-15/883 complied with the min and max limits for the respective versions of the LM140. The LM140H and LM140K may also be procured as JAN devices on slash sheet JM38510/107. www.national.com 6 0˚C ≤ TJ ≤ +150˚C, VI = 14V, IO = 500 mA, CI = 0.33 µF, CO = 0.1 µF, unless otherwise specified Symbol Parameter Conditions (Note 6) VO Output Voltage TJ = 25˚C ∆VO Line Regulation TJ = 25˚C ∆VO Load Regulation TJ = 25˚C LM7808C Units Min Typ 7.7 8.0 8.3 V 10.5V ≤ VI ≤ 25V 6.0 160 mV 11.0V ≤ VI ≤ 17V 2.0 80 5.0 mA ≤ IO ≤ 1.5A 12 160 250 mA ≤ IO ≤ 750 mA 4.0 80 11.5V ≤ VI ≤ 23V, 5.0 mA ≤ IO ≤ 1.0A, P ≤ 15W 7.6 Max VO Output Voltage IQ Quiescent Current ∆IQ Quiescent With Line 11.5V ≤ VI ≤ 25V Current Change With Load 5.0 mA ≤ IO ≤ 1.0A 0.5 TJ = 25˚C 4.3 mV 8.4 V 8.0 mA 1.0 mA VN Noise TA = 25˚C, 10 Hz ≤ f ≤ 100 kHz ∆VI/∆VO Ripple Rejection f = 120 Hz, IO = 350 mA, TJ = 25˚C VDO Dropout Voltage IO = 1.0A, TJ = 25˚C 2.0 V RO Output Resistance f = 1.0 kHz 16 mΩ 56 52 µV 72 dB IOS Output Short Circuit Current TJ = 25˚C, VI = 35V 0.45 A IPK Peak Output Current TJ = 25˚C 2.2 A ∆VO/∆T Average Temperature IO = 5.0 mA 0.8 mV/˚C Coefficient of Output Voltage Note 6: All characteristics are measured with a 0.22 µF capacitor from input to ground and a 0.1 µF capacitor from output to ground. All characteristics except noise voltage and ripple rejection ratio are measured using pulse techniques (tw ≤ 10 ms, duty cycle ≤ 5%). Output voltage changes due to changes in internal temperature must be taken into account separately. 7 www.national.com LM340/LM78XX LM7808C Electrical Characteristics LM340/LM78XX Typical Performance Characteristics Maximum Average Power Dissipation Maximum Average Power Dissipation 00778122 00778123 Maximum Power Dissipation (TO-263) (See Note 2) Output Voltage (Normalized to 1V at TJ = 25˚C) 00778124 00778125 Note: Shaded area refers to LM340A/LM340, LM7805C, LM7812C and LM7815C. Ripple Rejection Ripple Rejection 00778126 www.national.com 00778127 8 LM340/LM78XX Typical Performance Characteristics (Continued) Output Impedance Dropout Characteristics 00778129 00778128 Quiescent Current Peak Output Current 00778131 00778130 Note: Shaded area refers to LM340A/LM340, LM7805C, LM7812C and LM7815C. Dropout Voltage Quiescent Current 00778132 Note: Shaded area refers to LM340A/LM340, LM7805C, LM7812C and LM7815C. 00778133 9 www.national.com LM340/LM78XX Line Regulation 140AK-5.0, VIN = 10V, TA = 25˚C Line Regulation 140AK-5.0, IOUT = 1A, TA = 25˚C 00778106 00778105 Equivalent Schematic 00778107 www.national.com 10 LM340/LM78XX Application Hints The LM340/LM78XX series is designed with thermal protection, output short-circuit protection and output transistor safe area protection. However, as with any IC regulator, it becomes necessary to take precautions to assure that the regulator is not inadvertently damaged. The following describes possible misapplications and methods to prevent damage to the regulator. SHORTING THE REGULATOR INPUT When using large capacitors at the output of these regulators, a protection diode connected input to output (Figure 1) may be required if the input is shorted to ground. Without the protection diode, an input short will cause the input to rapidly approach ground potential, while the output remains near the initial VOUTbecause of the stored charge in the large output capacitor. The capacitor will then discharge through a large internal input to output diode and parasitic transistors. If the energy released by the capacitor is large enough, this diode, low current metal and the regulator will be destroyed. The fast diode in Figure 1 will shunt most of the capacitors discharge current around the regulator. Generally no protection diode is required for values of output capacitance ≤ 10 µF. 00778108 FIGURE 1. Input Short RAISING THE OUTPUT VOLTAGE ABOVE THE INPUT VOLTAGE Since the output of the device does not sink current, forcing the output high can cause damage to internal low current paths in a manner similar to that just described in the “Shorting the Regulator Input” section. 00778109 FIGURE 2. Regulator Floating Ground REGULATOR FLOATING GROUND (Figure 2) When the ground pin alone becomes disconnected, the output approaches the unregulated input, causing possible damage to other circuits connected to VOUT. If ground is reconnected with power “ON”, damage may also occur to the regulator. This fault is most likely to occur when plugging in regulators or modules with on card regulators into powered up sockets. Power should be turned off first, thermal limit ceases operating, or ground should be connected first if power must be left on. TRANSIENT VOLTAGES If transients exceed the maximum rated input voltage of the device, or reach more than 0.8V below ground and have sufficient energy, they will damage the regulator. The solution is to use a large input capacitor, a series input breakdown diode, a choke, a transient suppressor or a combination of these. 00778110 FIGURE 3. Transients When a value for θ(H–A) is found using the equation shown, a heatsink must be selected that has a value that is less than or equal to this number. θ(H–A) is specified numerically by the heatsink manufacturer in this catalog, or shown in a curve that plots temperature rise vs power dissipation for the heatsink. 11 www.national.com LM340/LM78XX Application Hints (Continued) Figures 6, 7 show the information for the SOT-223 package. Figure 6 assumes a θ(J–A) of 74˚C/W for 1 ounce copper and 51˚C/W for 2 ounce copper and a maximum junction temperature of 125˚C. HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS Both the TO-263 (“S”) and SOT-223 (“MP”) packages use a copper plane on the PCB and the PCB itself as a heatsink. To optimize the heat sinking ability of the plane and PCB, solder the tab of the plane. shows for the TO-263 the measured values of θ(J–A) for different copper area sizes using a typical PCB with 1 ounce copper and no solder mask over the copper area used for heatsinking. 00778141 FIGURE 6. θ(J–A) vs Copper (2 ounce) Area for the SOT-223 Package 00778139 FIGURE 4. θ(J–A) vs Copper (1 ounce) Area for the TO-263 Package As shown in the figure, increasing the copper area beyond 1 square inch produces very little improvement. It should also be observed that the minimum value of θ(J–A) for the TO-263 package mounted to a PCB is 32˚C/W. As a design aid, Figure 5 shows the maximum allowable power dissipation compared to ambient temperature for the TO-263 device (assuming θ(J–A) is 35˚C/W and the maximum junction temperature is 125˚C). 00778142 FIGURE 7. Maximum Power Dissipation vs TAMB for the SOT-223 Package Please see AN-1028 for power enhancement techniques to be used with the SOT-223 package. 00778140 FIGURE 5. Maximum Power Dissipation vs TAMB for the TO-263 Package www.national.com 12 LM340/LM78XX Typical Applications Fixed Output Regulator 00778113 Note: Bypass capacitors are recommended for optimum stability and transient response, and should be located as close as possible to the regulator. High Input Voltage Circuits 00778114 00778115 High Current Voltage Regulator 00778116 13 www.national.com LM340/LM78XX Typical Applications (Continued) High Output Current, Short Circuit Protected 00778117 Positive and Negative Regulator 00778118 www.national.com 14 LM340/LM78XX Physical Dimensions inches (millimeters) unless otherwise noted TO-3 Metal Can Package (K) NS Package Number K02A TO-263 Surface-Mount Package (S) NS Package Number TS3B 15 www.national.com LM340/LM78XX Physical Dimensions inches (millimeters) unless otherwise noted (Continued) TO-220 Power Package (T) NS Package Number T03B 3-Lead SOT-223 Package NS Package Number MP04A www.national.com 16 LM340/LM78XX Series 3-Terminal Positive Regulators Notes National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. 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