LT323

LT123A LINER | Alldatasheet

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TECHNOLOGY ‘ 5 Volt, 3 Amp Voltage Regulator FEATURES DESCRIPTION = Guaranteed 1% \\nitial Tolerance of Output Voltage © The LT123A/LT323A is an improved version of the = 3 Amp Output Current popular LM123/LM323 5 Volt, 3 Amp Regulator. = 30 Watt These new devices offer maximum initial output voit- = Full Internal Overload Protection age tolerance of 1% and maintain a maximum toler- = 100% Burn-in in Thermal Limit ance of 3% over worst case operating conditions. Line and load regulation are also improved by a factor of 2. These tightened specifications ease design and appli- cation problems since safety margins are improved. APPLICATIONS Also, errar budgets inter parts of the system can be expanded, and output voltages at the end of long sup- . oe oy regulators ply runs can be more accurately maintained. = On Card Regulation = Lab Supplies ; The LT123A/LT323A incorporates Linear Technol- = Instrumentation Supplies ogy’s advanced design, process and test techniques for improved quality and reliability over similar device types. Specifically, all devices are burned in by short- 4 | ing the output, thereby forcing the regulator into its current limit and eventually, thermal limit. This en- sures that all device protection features are function- al. A graph of the worst case output voltage, taking into account temperature, load and line variations, and power dissipation is shown below. For higher out- put current requirements, see the LT 1003, 5V, 5A reg- ulator data sheet. TS Precision 5 Volt Regulator Worst Case Output Voltage | | Tee eee vn urea a5 8 MLL “a 5 so LLLLLLLL LLL og |_oo | be 5 MMMM TANTALUM I I TANTALUM Sao VLLLLLALEL ELL = = = (LALEA TE ELELAT att tT Prt LETT TT yt 50-25 0 25 S50 75 100 125 150 JUNCTION TEMPERATURE (°C) SS LT Wye 4-149

LT123A/LT323A ., LM123/LM323 LS ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION Operating Junction Temperature Range LT123AK Storage Temperature Range Rona Lg2aK | LM323T ———) —_— TT PACKAGE ‘a TO-220 PLASTIC PRECONDITIONING: Thermal limit burn-in for all devices. ; ee ELECTRICAL CHARACTERISTICS (See Note 1) Pe ee SYMBOL CONDITIONS mn TYP MAX UNITS V, i = 25°C, fay amo Ate Se [eeretion [hate << | See lo 0 < lout < 3A (See Note 1) Pinactak ~sttnis oe mv la [Quiescent Current | 7.5V< Vn <1V.0< bur <3A fof 2 Tom es [Output Noise Voltage [Ty = 28°C, YOHz<t< 100KHz | [40 Pe “ee Te |e | Vy = 18V A Vy = 7.5V A a a fe Voltage 35 mv a == Case K Packag Nis hes 2B °crw The @ denotes the specifications which apply over the full operating temperature range. Note 1: Load and line regulation are tested with pulsed low duty cycle techniques where pulse width < tmsec and duty cycle < 5%. Note 2: Trin = —55°C for the LT123A/LM123 and 0°C for LT323A/ L823. Tmax = 150°C for LT123A/LM123 and 125°C for LT323A/ Note 3: Guaranteed, but not tested. 4-150 LT WE

ELECTRICAL CHARACTERISTICS (See Note 1) | | srmmo.__[mueren conor von We wae uns Your Output Voltage T) = 25°C, Vy = 7.5V, lout = 0 ee Vv Ii ak psn alae us an | an we an | Twax 0 < Ioyr < 3A, P< 30W (Note 2) 475 5.0 5.25 v Vi Line Regulati T, = 25°C, 7.5V < Vy < 15V mv eee Ve Load Regutati T, = 25°C, Vy = 7.5V seer eaten | | so | we | in [uiescent Gurrent | 75V < Vy < 16Y0<lgr 3A [o| 20 ~[ SSA ee [Output Noise Voltage [T= 25°C, tHe <t< toons | [4a POs "eee Te |e Current Limit Vw = 15V A Vin = 7.5¥ (See Note 4) A a Voltage mV a a — Case K Package 18 25 “c/w T Package 25 4.0 °C/W The @ denotes the specifications which apply over the full operating 4 | temperature range. Note 1: Load and line regulation are tested with pulsed low duty cycle techniques where pulse width < {msec and duty cycle < 5%. Note 2: Tin = —55°C for the LT123A/LM 123 and 0°C for LT323A/ LM323. Tmax = + 150°C for LT123A/LM123 and + 125°C for LT323A/LM323. Hote 3: Guaranteed, but not tested. Note 4: Isc at Viy = 7.5V is 6A max for LM323T. aE TYPICAL PERFORMANCE CHARACTERISTICS Dropout Voltage Output Voltage Temperature Drift 25 - a s | z °° at _ 5:10 } = Bis > hata geet 8 ' | k= 20008 2 500 eal _| Evo} + a4 || Besa Bef veg oe Bos p+} i i oh sieaeenes oO —75~-S0-25 0 25 SO 75 100 125 150 “50-25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (°C) TEMPERATURE (°C) ES LY Ltr 4-151

a TYPICAL PERFORMANCE CHARACTERISTICS suggested eat Suggested Heat juggested Heal Peak Available Output Current Sink Thermal Resistance Sink Thermal Resistance 6 0 SS SSS 0 SS SSS = | = mewn ——

2 Cr eS a a

:,| === wae eee 8 eee i= SNF Eee § 3 g 10 LN — g 0 Ww oe ——— CAN Ta = 25° . x =- 1° “TTPTLrl 2 AAS Srl oc 2 OARS Pitti yy oN SN ° 5 10 18 20 ' 0 5 10 15 20 2 30 36 ‘ oO 5 1 1 2 2 3 35 INPUT VOLTAGE (Vv) POWER DISSIPATION (WATTS) POWER DISSIPATION (WATTS) Output Impedance Output Noise Voltage Ripple Rejection er a= ov eH S| = t - a four = 0.58 TTT ath >

2 Lm Ct Se Fol AT IV

SAN 3 =1 i] fy = 10V, = ( ciate go Ste i El a Po A |g SEH Bw i—|_ CC = 8 CSc oon = = 0.1 uF See ea = LLL TY - (LUTE TT AT . 1 10 = 100 1k 10k =100k «1M 100 1k 10k 100k 1 10 100 1k 10k 100k = 1M FREQUENCY (Hz) BANOWIDTH (Hz) 1 POLE ROLLOFF FREQUENCY (Hz) Line Transient Response Load Transient Response Quiescent Current 75 14 eg 5 my] { 2 SB | a Z 0 era 22 0 — H BS | pAoae 10 uF [| 5 | |/ | y= 125° er img a ce ze n ay U “ato TO s | fi set |i NMi| . i 7 ae Beep ee © os a 2 OPES ERE fee oO 1 2 3 4 5 t') 1 2 3 4 5 Oo 4 8 12 16 2c TIME (us) TIME (us) INPUT VOLTAGE (V) ———— 4-152 LT Wnte

— ed APPLICATIONS INFORMATION Bypass Capacitors: The LT123A does not require an Cee SNE LOW output capacitor for resistive loads. For almost all ap- J plications, however, a 1yF or larger solid tantalum ca- en pacitor should be used at the output within 2” of the ow regulator to improve the output impedance at high fre- quencies. For applications where very low high fre- raw surrty 12m. LomD quency impedance is required, a 10uF solid tantalum output capacitor is recommended. Total output ca- pacitance either local or distributed may beincreased ~ Y without limit. THS RESISTANCE DOES NOT \\ CONTRIBUTE TO LOAD REGULATION HI CURRENT PATH A 2uF or larger solid tantalum capacitor or a 25yF alu- . ‘ . minum capacitor, must be used at the input ifthe regu- @w Supply: Transformer, diode, and capacitor selec- lator is more than 4” away from the large rectifier tion for the raw supply to the LT 123A is very important capacitor. because of the conflicting requirements for reliability, . efficiency, and resistance to ‘‘brown-out” conditions. High secondary voltage on the transformer will cause Avoiding Ground Loops: For best regulation, the ground unnecessarily high power dissipation in the regulator. pin of the LT123A should be tied directly to the load "00 low a secondary voltage will cause the reguiator 4 | point as shown. This prevents excess drop in load UtPut to drop out of regulation with only a small re- voltage caused by load current flowing through the duction in AC mains voltage. The following formula ground return lead. This is essentially a Kelvin con- gives a good starting point for transformer selection. nection for the low side of the regulator. A Kelvin con- ‘This formula iter diod a center tapped transformer, nection cannot be made for the high output of — USing two rectifier diodes. regulator because only three pins are available on the where: package. Therefore, every attempt should be madeto Vor =SV 7 minimize the resistance between the output pin of the Yoo = vaulter input-output differential of the regulator and the load. #18 gauge hookup wire has —Vaecr._ = Rectifier forward drop at Sloyr resistance of 0.006 ohms per foot. This translates to Var = %P-p capacitor ripple voltage 0.36% change in load voltage at full load current. The we (8.3. X 1074) (lout) LT123A is specified at 1% maximum load regulation, ; 2c so one foot of wire represents a significant loss of reg- Yvow = el voltage for the transformer ulation. If connectors are used, careful consideration Vig = Lowest expected line voltage (RMS) must be given to contact resistance, especially if the ‘our = DC output current ole i is siblested tonasty ambients, vibration, OF «4.4 is a nominal load regulation factor for the multiple insertions. transformer ee LT Witne 4-153

Example: lout = 2.5A, Vour = 5V th e<ny-7The filter capacitor should be at /east2000uF per amp Assume: aera hl = NG ~ 8000uF of load current to minimize capacitor heating and rip- (63 x 107% (25) : ple voltage. The diodes should be rated at 5-6 amps Va = ex) 0.83V even though their average current is only 1.5A at full 5425+ 114083) (115 rated load current. The reason for this is that although Vans = 7 (2) (1.1) the average current is 1.5A, the RMS current is typi- = 8.03 Vays 2 Cally twice this value. In addition, the diode must with- ' stand very high surge currents during power turn-on. Vout + Voo + Vi v yy Vaws = het ene (qe) (1.1") This surge can be 10-20 times the DC rating of the laws = (lout) (1.2) supply, depending on capacitor size and wiring resis- tance and inductance. ee, TYPICAL APPLICATIONS Dy : | I ‘pas Vour ra RES poe a Vout : | 7 BLOW BLOW qit* a: -_| INPUT CROWBAR OUTPUT CROWBAR + 2 AND D1 MUST WITHSTAND LARGE SURGE CURRENTS * THE 6.4V ZENER IS INTERNAL TO THE LT123A. UNTIL THE 5A FUSE BLOWS. PEAK SURGE CURRENT IS oy Q1 MUST BE ABLE TO WITHSTAND CONTINUOUS CURRENTS UMITED ONLY BY THE FUSE, WIRING, AND FILTER CAP OF 5A IF ADDITIONAL SYSTEM SHUTDOWN IS NOT USED. RESISTANCE. tt TRIP POINT IS APPROXIMATELY 7.3V. ~ a 4-154 OWE

[bet [pe pT] |* “dite a ae TT REE ETT ; PACKAGE DESCRIPTION K Package STEEL METAL CAN T Package TO-220 =coo a Soc Ee = alo AI ine 4-155