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; ' LT337A/LM337 TECHNOLOGY Negative Adjustable Regulator FEATURES DESCRIPTION = Guaranteed 1% Initial Voltage Tolerance The LT137A/LT337A negative adjustable regulators = Guaranteed 0.01%/V Line Regulation will deliver up to 1.5Amps output current over an out- = Guaranteed 0.5% Load Regulation put voltage range of — 1.2V to —37V. Linear Technol- = Guaranteed 0.02%/W Thermal Regulation ogy has made significant improvements in these ® 100% Burn-in in Thermal Limit regulators compared to previous devices, such as bet- ter line and load regulation, and a maximum output voltage error of 1%. Every effort has been made to make these devices APPLICATIONS easy to use and difficult to damage. Internal current and power limiting coupled with true thermal limiting a Adjustable Power Supplies prevents device damage due to overloads or shorts, = System Power Supplies even if the regulator is not fastened to a heat sink. = Precision Voltage/Current Regulators = On-Card Regulators Maximum reliability is attained with Linear Technol- ogy’s advanced processing techniques combined with 4 | a 100% burn-in in the thermal limit mode. This as- sures that all device protection circuits are working and eliminates field failures experienced with other regulators that receive only standard electrical testing. Negative Regulator w Output Voltage Error oe So e «| a 8") A a boy he, es ae i Sak at s,{ [|i i Bo Aer Ti resistors' 1 BET Tae gs 5 ? T3378 -WN mA Yo ~Vour = 125v (14-22) 5 EE Bessa som | ie cee aaa ' + AO mena (tea! -) o ELL TT 1250 2 46810 2 40 100 OUTPUT VOLTAGE AT Ne 4-157
i ooo’ ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION Operating Junction Temperature Range ADJ Vour 1A \\ * Storage Temperature Range OASEISYN Thigg7K | ASSN LM337H —<—— PART NO. PRECONDITIONING ay pera 100% THERMAL LIMIT BURN-IN T PACKAGE OE ELECTRICAL CHARACTERISTICS (See Note 1) er ee Veer Reference Voltage Vin—Vour| = 5Y, lour = 10mA, ee eat 1, = 25°C 1238 1.250 1262 | 1225 — 1.260 - 1275 v ‘Oma be Yor 404 Pune Aes = 1200 - 1.250 -1:300 v AVout Load Regulation 10MA < lout < Iyax, (See Note 2) alr Ty = 25°C, [Vour| < 5V 5 5 5 5 mv Ty = 25°C, |Vour| > 5V 01 605 03 05 % [Vour| < 5¥ 10 50 20 «50 mv Vout | > 5V 0.2 4.0 - 03 1.0 % ' ae aan om 0.02 0.05 eV ne Cros = 0 fer, eee 60 4B Cans = 10uF m0 | we 8 [Thermal Regulation (T= 25°C, 10msec Pulse | | 002 oz | 0002002 | a thoy [Adjust Pin Current | fo 65100 | uA ew ee el eel iets Vin—Vour| < 10V 1.2 3.0 mA Isc Current Limit |Vin=Vour| < 15V, K and T Package 15, 2.2 32 15 22 A H Package 0.5 0.8 15 05 08 A [Vn=Vour| = 40v, K and T Package 024 04 10 024 04 A T= 25°C H Package 015 0.25 «05 0.15 0.25 A ee |, | fg [ote preemie Pe [ee (% of Vout) Junction to Case K Package “cw 4-158 LT Wie
ELECTRICAL CHARACTERISTICS (See Note 1) M337 Vi Reference Voltage TVan—Vourl = 5V. lour = 10mA, eee AVout. Load Regulation 10MA < lout < Imax, (See Note 2 & EY 3) ial T, = 25°C, [Vour| < 5V 5 25 15 50 mv Ty = 25°C, |Vour| > 5V 0.4 05 03 10 % \\Vour] < 5V 10 50 20 70 mv Vour| > 5V 02 1.0 03 15 % Na 1 Line Regulation wv <|Vin~ Vour| < 40V, (See Note ee | aww i, = 25°C toms Doi | 0.01 0.04 wv 901 603. | 0.02 0.07 RIV Ripple Rejection Vour = —10V, f = 120Hz ee Gos =0 Poa 60 a Cans = 10uF | 70,80. | 6 B Alay Adjust Pin Current Change 10MA < lout < | AE ai S| uA 3V_<|Vw — Vout] < 40V. Bae 5.12 | Minimum Load Current Va Von] < 40V eas uh Ise Current Limit |Vin—Vour | = 15¥, Mestre nak K and T Package |e 22 S57) 15 = 22 A H Package poOe 08 15) 05 08 A [Vw—Vour | = 40v, ee : K and T Package PO 08 610 | 015 «04 A 1 = 25°C H Package meee uee | 010 0.17 A Vox __| Temperature Stability of Output pe “Temp” _| Voltage (Note 4) iets so aa % a ATime en RMS Output Noise Ta = 25°C, 10Hz < f < 10kHz 0.003 % (%% of Vo Oc Thermal Resistance H Package heen Gags | 2. «5 °cIW sunction to Case K Package kag 28 80 | 23-30 °C/W T Package Sees | a5 “cw The @ denotes the specifications which apply over the full operating Note 2: Testing is done using a pulsed low duty cycle technique. See temperature range. thermal regulation specifications for output changes due to heating The shaded electrical specifications indicate those parameters effects. Load regulation is measured on the output pin at a point 1/8” which have been improved or guaranteed test limits provided for the ne ew portion! ti package iat page of the first time. it . Note 1: Unless otherwise indicated, these specifications apply: Note 3: Load Regulation for the LT337AT is the same as for LM337T. [Vin — Vour| = 5V; and lour = 0.1A for the H package, loyr = 0.5A Note 4: Guaranteed on LT137A and LT337A, but not 100% tested in for the K and T packages. Power dissipation is internally limited. Production. However, these specifications apply for power dissipation up to 2W for the H package and 20W for the K and T packages. Imax = 1.5A for the K and T packages, and 0.2A for the H package. . ae EEE
TYPICAL PERFORMANCE CHARACTERISTICS Dropout Voltage Temperature Stability Minimum Load Current “OTT Ee 1.6 eA te} A ee A =o. bs ee EI Fz Co Pa Td 8 ri] gs LT Evo 2 see be ee eat eee) Ss} eH BD Perce) 0.2 BSS coe AE we o4 08 1.2 1.6 20 on ~60-25 0 25 50 75 100 125 150 a 10 20 30 40 OUTPUT CURRENT (A) TEMPERATURE (°C) INPUT-OUTPUT DIFFERENTIAL (V) Ripple Rejection Ripple Rejection Ripple Rejection wT) ® [| SOT Se ee eNO pee Te meer il gS z L I! poe Et CPT Eo | To— #, aN 2 patra] || Blt NAO ETT ERT CEES RET ot 9 Line i 9 Lice 0 10 20 -30 -40 10 100 1k 10k 100k 1M 0.01 O41 1 10 OUTPUT VOLTAGE (V) FREQUENCY (Hz) OUTPUT CURRENT (A) Output Impedance Line Transient Response Load Transient Response NO) ee SS O8 06 woo ote IT eel Pe ed a — CRY. | #8 pew y Tj = 25°C =.= Soe ‘ 55 [Soaps = tose | 7 oes aay a CPN | 28 02 w/a oo oe . [| _ 08 Tor Se eo a e” -\\ Meee ian 10 100 1k 10k 100k 1M ~ oO 10 20 0 40 - oO 10 20 30 40 FREQUENCY (Hz) TIME (us) TIME (48) TE 4-160 LT eee
eh Senna, TYPICAL PERFORMANCE CHARACTERISTICS Load Regulation* Current Limit Adjustment Current TTT IT] 3 T 80 i : EEE Ge me a " EE Za Ll} TTT ty i en 3 | erp eae ] e2 HEA as ey Noe e ag LL eT NN CSS ee EC Ee ce 2 1} Pes NO ge pO engl Se TTT | fi yy iT S|
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0 04 08 12 1.6 20 oO 10 20 w 40 -75-50-25 0 25 50 75 100 125 150 OUTPUT CURRENT (A) (INPUT-OUTPUT DIFFERENTIAL (V) ‘TEMPERATURE (°C) “The LT137A/337A has load regulation com- pensation which makes the typical unit read close to zero. This band represents the typi- cal production spread. eee APPLICATION INFORMATION absorb the current, but care must be taken in no-load . situations where Ry and Rp have high values. The 4 | Output Voltage: The output voltage is determined by maximum value for the operating current, which must two external resistors, Ry & Re (See Figure 1). The ex- he absorbed, is 5mA for the LT137A. If input-output act formula for the output voltage is: voltage differential is less than 10V, the operating cur- Vout = Vea ( 14 fe ) + bos Po) rent that must be absorbed drops to 3mA. a Where: Vper = Reference Voltage, lap = Adjustment " Pin Current. In most applications, the second term is + Sur Re > small enough to be ignored, typically about 0.5% of oe, aS 3, Vour- In more critical applications, the exact formula RI should be used, with I4py equal to 65,a. Solving for Ro yields: rae ae WN Mo SEIOTA our — Vor Ry = Nout = Veo See Vat | RT Figure 1 Smaller values of R, and Rp will reduce the influence of ’ laoy On the output voltage, but the no-load current EXAMPLES: drain on the regulator will be increased. Typical values __*- A precision 10V regulator to supply up to tAmp load current. for Ry are between 1000 and 3009, giving 12.5mA a. Select Ry = 1002 to minimize effect of tans and 4.2mA no-load current respectively. There is an ——, calculate Rp = Yout— Yaw _ _10V— 1.25V_ _ r940 additional consideration in selecting Ry, the minimum Yau = nop 2M — eeu load current specification of the regulator. The operat- > 4 15y regulator to run off batteries ay Supply SOmA, ing current of the LT137A flows from input to output. If Vin MAX = 25V this current is not absorbed by the load, the output of a. To minimize battery drain, select R, as high as possible the regulator will rise above the regulated value. The _ 126V _ Current drawn by R; and Re is normally high enough to Rim cna S178. use 4040, 1% ee LI We 4-161
LT337A/LM337 . a b. The high value for Ry will exaggerate the error due to Ian, SO the exact formula to calculate Ra should be used. the, Re + fp — Nour = Vat 15V = 125V___ gaan a Fo, Ye — a aN — 65 x 108 — wee Use Rp = 45300 a tnao02 Capacitors and Protection Diodes: An output capacitor, -Vw Your C3, is required to provide proper frequency compen- CRESS sation of the regulator feedback loop. A 1uF or larger solid tantalum capacitor is generally sufficient for this purpose if the 1MHz impedance of the capacitor is 20 “2 \\nrast'. Netcare ae i Te ee ore ovale or less. High Q capacitors, such as Mylar, are not rec- "han 20uF and Nour's ger han neous ger nan = 254 ommended because they tend to reduce the phase Figure 2 margin at light load currents. Aluminum electrolytic Capacitors may also be used, but the minimum value praper Connection of Divider Resistors: The LT137A has . . I inches of the regulator to keep lead impedance to 4 package. To prevent degradation of load regulation, minimum. The following caution should be noted: if the resistors which set output voltage, R1 and R2, the output voltage is greater than 6Vand an output ca- must be connected as shown in Figure 3. Note that the pacitor greater than 20yF has been used, itis possible positive side of the load has a true force and sense to damage the regulator if the input voltage becomes (Kelvin) connection, but the negative side of the load Shorted, due to the output capacitor discharging into Gogg not , the regulator. This can be prevented by using diode DI ° (see Figure 2) between the input and the output. - Les rx cosa The input capacitor, C2, is only required if the regula- << tor is more than 4 inches from the raw supply filter = = capacitor. Bypassing the Adjustment Pin: The adjustment pin of the LT137A may be bypassed with a capacitor to ground, C1, to reduce output ripple, noise, and impedance. — - These parameters scale directly with output voltage if _,, eae Dea a the adjustment pin is not bypassed. A bypass capaci- Ss \\ tor reduces ripple, noise, and impedance to that of a Gennes Ry ecty lo Lee 1.25V regulator. Ina 15V regulator for example, these the length ofthis lead parameters are improved by 15V/1.25V = 12 to 1. Figure 3 This improvement holds only for those frequencies where the impedance of the bypass capacitor is less | R1 should be connected directly to the output lead of than R;. Ten microfarads is generally sufficient for the regulator, as close as possible to the specified 60Hz power line applications where the ripple fre- point 1/8” from the case. R2 should be connected to quency is 120Hz, since X, = 130. The capacitor __ the positive side of the load separately from the posi- should have a voltage rating at least as high as the _tive (ground) connection to the raw supply. With this output voltage of the regulator. Values larger than arrangement, load regulation is degraded only by the 10,F may be used, but if the output is larger than 25V, _resistance between the regulator output pin and the a diode, D2, should be added between the output and _load. If R1 is connected to the load, regulation will be adjustment pins (see Figure 2). degraded. OE 4-162 LT WEAR
TYPICAL APPLICATIONS High Stability Regulator The output stability, load regulation, line regulation, thermal regulation, temperature drift, long term drift, = use 2°" |, and noise, can be improved by a factor of 6.6 over the we standard regulator configuration. This assumes a eG x | aun zener whose drift and noise is considerably better — ; * than the regulator itself. The LM329B has 20PPM/°C hc deo weal ; maximum drift and about 10 times lower noise than ™ bet ad Ne the regulator. Se R= a” 2088 «ae Dual Tracking Supply + 1.25V to + 20V In the application shown below, regulators #2 to “N” Mal Tracking SuPIY = °* will track regulator #1 to within + 24mV initially, and to + 60mV over all load, line, and temperature condi- +m +Nour tions. If any regulator output is shorted to ground, all im other outputs will drop to ~ —2V. Load regulation of ai tl one 1 oy regulators 2 to “N”’ will be improved by Voyr/1.25V % FA waooe compared to a standard regulator, so regulator #1 al Tre should be the one which has the lowest load current. Woura 3 Sk RS 4 | Multiple Tracking Regulators + to a + arnt = a ers WF =v pole we ton —Wn rs PEE out} Voor * © Ay oF Rg may be trimmed slightly to improve tracking [4 Current Regulator a ne ! SOLD ae ! =e | ° Rs T . ri an? --4 [2 soeene ‘ 1.25 Bead : = ry Ma T= 65yA + . i Hin 7S Rea TANTALUM (0.82 < Rg< 2509) ee ——— AT WEAR 4-163
- és LC jr a 3 ; io J, Plas J Yo) JELo 4 CLEFT Pt 4 Co U a PACKAGE DESCRIPTION K Package TO-3 STEEL Metal Can T Package T0-220 Plastic 3-Lead Metal Can Package (H) we 0395-040 | gists jesresom a wa pet BEC] ae | sts LT mea ~ 4 sat 1197 359620258) Ter Toseo, oso. nee 2 aw - Tarot eae Se ial ia” coll eseeses nae aN Tey 0.10020010 ee om 028-0004 3 a arose ors 199 arias \\ [T tawx Tex] [time Ten] [tome Te] ef | at |e | ve | [ev [we | cow [at | we [won | ee 4-164 LY Wiitre