FEATURES DESCRIPTION n Wide Input Voltage Range: 3V to 60V n Low Quiescent Current: 6mA n Internal 5A Switch

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1 FEATURES DESCRIPTION n Wide Input Votage Range: 3V to 6V n Low Quiescent Current: 6mA n Interna 5A Switch (2.5A for LT1171, 1.25A for LT1172) n Shutdown Mode Draws Ony 5μA Suppy Current n Very Few Externa Parts Required n Sef-Protected Against Overoads n Operates in Neary A Switching Topoogies n Fyback-Reguated Mode Has Fuy Foating Outputs n Comes in Standard 5-Pin Packages n LT1172 Avaiabe in 8-Pin MiniDIP and Surface Mount Packages n Can Be Externay Synchronized APPLICATIONS n Logic Suppy 5V at 1A n 5V Logic to ±15V Op Amp Suppy n Battery Upconverter n Power Inverter ( to ) or ( to ) n Fuy Foating Mutipe Outputs USER NOTE: This data sheet is ony intended to provide specifications, graphs, and a genera functiona description of the LT117/LT1171/LT1172. Appication circuits are incuded to show the capabiity of the LT117/LT1171/LT1172. A compete design manua (AN19) shoud be obtained to assist in deveoping new designs. This manua contains a comprehensive discussion of both the LT17 and the externa components used with it, as we as compete formuas for cacuating the vaues of these components. The manua can aso be used for the LT117/LT1171/LT1172 by factoring in the higher frequency. A CAD design program caed SwitcherCAD is aso avaiabe. LT117/LT1171/LT1172 1kHz, 5A, 2.5A and 1.25A High Efficiency Switching Reguators The LT 117/LT1171/LT1172 are monoithic high powerswitching reguators. They can be operated in a standard switching configurations incuding buck, boost, fyback, forward, inverting and Cuk. A high current, high efficiency switch is incuded on the die aong with a osciator, contro and protection circuitry. Integration of a functions aows the LT117/LT1171/LT1172 to be buit in a standard 5-pin TO-3 or TO-22 power package as we as the 8-pin packages (LT1172). This makes them extremey easy to use and provides bust proof operation simiar to that obtained with 3-pin inear reguators. The LT117/LT1171/LT1172 operate with suppy votages from 3V to 6V, and draw ony 6mA quiescent current. They can deiver oad power up to 1W with no externa power devices. By utiizing current-mode switching techniques, they provide exceent AC and DC oad and ine reguation. The LT117/LT1171/LT1172 have many unique features not found even on the vasty more difficut to use ow power contro chips presenty avaiabe. They use adaptive antisat switch drive to aow very wide ranging oad currents with no oss in efficiency. An externay activated shutdown mode reduces tota suppy current to 5μA typicay for standby operation. L, LT, LTC, LTM, Linear Technoogy, the Linear ogo and SwitcherCAD are registered trademarks of Linear Technoogy Corporation. A other trademarks are the property of their respective owners. TYPICAL APPLICATION C3* 1μF Boost Converter (5V to 12V) 5V LT117 L1** 5μH 1k 1μF MB3 L2 1μH C3 1μF 1μF OUTPUT FILTER 1.7k 1% 1.24k 1% Maximum Output Power* *REQUIRED IF INPUT LEADS 2" ** COILTRONICS /1/2 TA1 PULSE ENGINEERING V 1A POWER (W) ** LT117 BOOST FLYBACK BUCK-BOOST V O = 5V BUCK-BOOST V O = 3V INPUT VOLTAGE (V) * ROUGH GUIDE ONLY. BUCK MODE P OUT = (5A)(V OUT ) SPECIAL TOPOLOGIES DELIVER MORE POWER. ** DIVIDE VERTICAL POWER SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172. LT117/1/2 TA fg 1

2 LT117/LT1171/LT1172 ABSOLUTE MAXIMUM RATINGS Suppy Votage LT117/LT1171/LT1172HV (Note 2)...6V LT117/LT1171/LT1172 (Note 2)...4V Switch Output Votage LT117/LT1171/LT1172HV...75V LT117/LT1171/LT V LT1172S8...6V Feedback Pin Votage (Transient, 1ms)... ±15V Storage Temperature Range C to 15 C Lead Temperature (Sodering, 1 sec...3 C (Note 1) Operating Junction Temperature Range LT117M/LT1171M (OBSOLETE) C to 15 C LT1172M C to 125 C LT117/LT1171/LT1172HVC, LT117/LT1171/LT1172C (Oper.)... C to 1 C LT117/LT1171/LT1172HVC LT117/LT1171/LT1172C (Sh. Ckt.)... C to 125 C LT117/LT1171/LT1172HVI, LT117/LT1171/LT1172I (Oper.)... 4 C to 1 C LT117/LT1171/LT1172HVI, LT117/LT1171/LT1172I (Sh. Ckt.)... 4 C to 125 C PIN CONFIGURATION NC* TOP VIEW E2 E1 J8 PACKAGE 8-LEAD CERDIP T JMAX = 125 C, θ JA = 1 C/W * Do not connect Pin 4 of the LT1172 DIP or SO to externa circuitry. This pin may be active in future revisions. FRONT VIEW Q PACKAGE 5-LEAD DD T JMAX = 1 C, θ JA = * C/W * θ wi vary from approximatey 25 C/W with 2.8 sq. in. of 1oz. copper to 45 C/W with.2 sq. in. of 1oz. copper. Somewhat ower vaues can be obtained with additiona copper ayers in mutiayer boards. BOTTOM VIEW 1 4 K PACKAGE 4-LEAD TO-3 METAL CAN LT117MK: T JMAX = 15 C, θ JC = 2 C/W, θ JA = 35 C/W LT117CK: T JMAX = 1 C, θ JC = 2 C/W, θ JA = 35 C/W LT1171MK: T JMAX = 15 C, θ JC = 4 C/W, θ JA = 35 C/W LT1171CK: T JMAX = 1 C, θ JC = 4 C/W, θ JA = 35 C/W LT1172MK: T JMAX = 15 C, θ JC = 8 C/W, θ JA = 35 C/W LT1172CK: T JMAX = 1 C, θ JC = 8 C/W, θ JA = 35 C/W Based on continuous operation. T JMAX = 125 C for intermittent faut conditions. OBSOLETE NC 1 NC NC 6 NC 7 NC 8 TOP VIEW NC 15 NC 14 E E NC 9 NC CASE IS SW PACKAGE 16-LEAD PLASTIC SO WIDE T JMAX = 1 C, θ JA = 15 C/W Based on continuous operation. T JMAX = 125 C for intermittent faut conditions. NC* N8 PACKAGE 8-LEAD PDIP TOP VIEW E2 E1 S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 1 C, θ JA = 1 C/W (N) T JMAX = 1 C, θ JA = 12 C/W to 15 C/W depending on board ayout (S) * Do not connect Pin 4 of the LT1172 DIP or SO to externa circuitry. This pin may be active in future revisions. FRONT VIEW T PACKAGE 5-LEAD PLASTIC TO-22 LT117CT/LT117HVCT: T JMAX =1 C, θ JC = 2 C/W, θ JA = 75 C/W LT1171CT/LT1171HVCT: T JMAX =1 C, θ JC = 4 C/W, θ JA = 75 C/W LT1172CT/LT1172HVCT: T JMAX =1 C, θ JC = 8 C/W, θ JA = 75 C/W Based on continuous operation. T JMAX = 125 C for intermittent faut conditions fg

3 LT117/LT1171/LT1172 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1172MJ8#PBF LT1172MJ8#TRPBF 8-Lead CERDIP 55 C to 125 C LT1172CJ8#PBF (OBSOLETE) LT1172CJ8#TRPBF 8-Lead CERDIP C to 1 C LT117MK#PBF (OBSOLETE) LT117MK#TRPBF 4-Lead TO-3 Meta Can 55 C to 125 C LT117CK#PBF (OBSOLETE) LT117CK#TRPBF 4-Lead TO-3 Meta Can C to 1 C LT1171MK#PBF (OBSOLETE) LT1171MK#TRPBF 4-Lead TO-3 Meta Can 55 C to 125 C LT1171CK#PBF (OBSOLETE) LT1171CK#TRPBF 4-Lead TO-3 Meta Can C to 1 C LT1172MK#PBF (OBSOLETE) LT1172MK#TRPBF 4-Lead TO-3 Meta Can 55 C to 125 C LT1172CK#PBF (OBSOLETE) LT1172CK#TRPBF 4-Lead TO-3 Meta Can C to 1 C LT1172CN8#PBF LT1172CN8#TRPBF 8-Lead PDIP or 8-Lead Pastic SO C to 1 C LT1172IN8#PBF LT1172IN8#TRPBF 8-Lead PDIP or 8-Lead Pastic SO 4 C to 1 C LT1172CS8#PBF LT1172CS8#TRPBF Lead PDIP or 8-Lead Pastic SO C to 1 C LT1172IS8#PBF LT1172IS8#TRPBF 1172I 8-Lead PDIP or 8-Lead Pastic SO 4 C to 1 C LT117CQ#PBF LT117CQ#TRPBF 5-Lead DD C to 1 C LT117IQ#PBF LT117IQ#TRPBF 5-Lead DD 4 C to 1 C LT117HVCQ#PBF LT117HVCQ#TRPBF 5-Lead DD C to 1 C LT1171CQ#PBF LT1171CQ#TRPBF 5-Lead DD C to 1 C LT1171IQ#PBF LT1171IQ#TRPBF 5-Lead DD 4 C to 1 C LT1171HVCQ#PBF LT1171HVCQ#TRPBF 5-Lead DD C to 1 C LT1171HVIQ#PBF LT1171HVIQ#TRPBF 5-Lead DD 4 C to 1 C LT1172CQ#PBF LT1172CQ#TRPBF 5-Lead DD C to 1 C LT1172HVCQ#PBF LT1172HVCQ#TRPBF 5-Lead DD C to 1 C LT1172HVIQ#PBF LT1172HVIQ#TRPBF 5-Lead DD 4 C to 1 C LT1172CSW#PBF LT1172CSW#TRPBF 16-Lead Pastic SO Wide C to 1 C LT117CT#PBF LT117CQ#TRPBF 5-Lead Pastic TO-22 C to 1 C LT117IT#PBF LT117IT#TRPBF 5-Lead Pastic TO-22 4 C to 1 C LT117HVCT#PBF LT117HVCT#TRPBF 5-Lead Pastic TO-22 C to 1 C LT117HVIT#PBF LT117HVIT#TRPBF 5-Lead Pastic TO-22 4 C to 1 C LT1171CT#PBF LT1171CT#TRPBF 5-Lead Pastic TO-22 C to 1 C LT1171IT#PBF LT1171IT#TRPBF 5-Lead Pastic TO-22 4 C to 1 C LT1171HVCT#PBF LT1171HVCT#TRPBF 5-Lead Pastic TO-22 C to 1 C LT1171HVIT#PBF LT1171HVIT#TRPBF 5-Lead Pastic TO-22 4 C to 1 C LT1172CT#PBF LT1172CT#TRPBF 5-Lead Pastic TO-22 C to 1 C LT1172HVCT#PBF LT1172HVCT#TRPBF 5-Lead Pastic TO-22 C to 1 C Consut LTC Marketing for parts specified with wider operating temperature ranges. Consut LTC Marketing for information on non-standard ead based finish parts. For more information on ead free part marking, go to: For more information on tape and ree specifications, go to: fg 3

4 LT117/LT1171/LT1172 ELECTRICAL CHARACTERISTICS The denotes the specifications which appy over the fu operating temperature range, otherwise specifications are at T A = 25 C. = 15V, =.5V, V = V REF, output pin open, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V REF Reference Votage Measured at Feedback Pin =.8V I B Feedback Input Current V = V REF g m Error Ampifier Transconductance ΔI C = ±25μA Error Ampifier Source or Sink Current = 1.5V Error Ampifier Camp Votage Reference Votage Line Reguation Hi Camp, V = 1V Lo Camp, V = 1.5V 3V V MAX =.8V V V na na μmho μmho μa μa V V.3 %/V A V Error Ampifier Votage Gain.9V 1.4V 5 8 V/V Minimum Input Votage (Note 5) V I Q Suppy Current 3V V MAX, =.6V 6 9 ma Contro Pin Threshod Duty Cyce = V V Norma/Fyback Threshod on Feedback Pin V V Fyback Reference Votage (Note 5) I = 5μA V V Change in Fyback Reference Votage.5 I 1mA V Fyback Reference Votage Line Reguation (Note 5) I = 5μA.1.3 %/V 7V V MAX Fyback Ampifier Transconductance (g m ) ΔI C = ±1μA μmho Fyback Ampifier Source and Sink Current =.6V Source 15 7 I = 5μA Sink 25 7 BV Output Switch Breakdown Votage 3V V MAX, LT117/LT1171/LT I SW = 1.5mA LT117HV/LT1171HV/LT1172HV 75 LT1172S8 6 V SAT Output Switch On Resistance (Note 3) LT117 LT1171 LT1172 Contro Votage to Switch Current Transconductance LT117 LT1171 LT1172 I LIM Switch Current Limit (LT117) Duty Cyce = 5% T J 25 C Duty Cyce = 5% T J < 25 C Duty Cyce = 8% (Note 4) (LT1171) Duty Cyce = 5% T J 25 C Duty Cyce = 5% T J < 25 C Duty Cyce = 8% (Note 4) (LT1172) Duty Cyce = 5% T J 25 C Duty Cyce = 5% T J < 25 C Duty Cyce = 8% (Note 4) ΔI IN Suppy Current Increase During Switch ΔI SW On-Time f Switching Frequency ma ma V V V Ω Ω Ω A/V A/V A/V A A A A A A A A A ma/a khz khz fg

5 LT117/LT1171/LT1172 ELECTRICAL CHARACTERISTICS The denotes the specifications which appy over the fu operating temperature range, otherwise specifications are at T A = 25 C. = 15V, =.5V, V = V REF, output pin open, uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS DC MAX Maximum Switch Duty Cyce % Shutdown Mode 3V V MAX 1 25 μa Suppy Current =.5V Shutdown Mode 3V V MAX mv Threshod Votage 5 3 mv Fyback Sense Deay Time (Note 5) 1.5 μs Note 1: Stresses beyond those isted under Absoute Maximum Ratings may cause permanent damage to the device. Exposure to any Absoute Maximum Rating condition for extended periods may affect device reiabiity and ifetime. Note 2: Minimum effective switch on time for the LT117/LT1171/ LT1172 (in current imit ony) is.6μs. This imits the maximum safe input votage during an output shorted condition. Buck mode and inverting mode input votage during an output shorted condition is imited to: ( ) I L ( ) Vf (max, output shorted) = 15V R buck and inverting mode ( t) ( f) R = Inductor DC resistance I L = 1A for LT117, 5A for LT1171, and 2.5A for LT1172 Vf = Output catch diode forward votage at I L t =.6μs, f = 1kHz switching frequency Maximum input votage can be increased by increasing R or Vf. Externa current imiting such as that shown in AN19, Figure 39, wi provide protection up to the fu suppy votage rating. in Figure 39 shoud be reduced to 2pF. Transformer designs wi toerate much higher input votages because eakage inductance imits rate of rise of current in the switch. These designs must be evauated individuay to assure that current imit is we controed up to maximum input votage. Boost mode designs are never protected against output shorts because the externa catch diode and inductor connect input to output. Note 3: Measured with in hi camp, V =.8V. I SW = 4A for LT117, 2A for LT1171, and 1A for LT1172. Note 4: For duty cyces (DC) between 5% and 8%, minimum guaranteed switch current is given by I LIM = 3.33 (2 DC) for the LT117, I LIM = 1.67 (2 DC) for the LT1171, and I LIM =.833 (2 DC) for the LT1172. Note 5: Minimum input votage for isoated fyback mode is 7V. V MAX = 55V for HV grade in fuy isoated mode to avoid switch breakdown fg 5

6 LT117/LT1171/LT1172 TYPICAL PERFORMANCE CHARACTERISTICS 16 Switch Current Limit vs Duty Cyce* Minimum Input Votage Switch Saturation Votage SWITCH CURRENT (A) C 125 C 25 C * DIVIDE VERTICAL SCALE BY TWO FOR LT1171, BY FOUR FOR LT DUTY CYCLE (%) MINIMUM INPUT VOLTAGE (V) SWITCH CURRENT = I MAX SWITCH CURRENT = A TEMPERATURE ( C) SWITCH SATURATION VOLTAGE (V) C 1 C SWITCH CURRENT (A)* 25 C 55 C * DIVIDE CURRENT BY TWO FOR LT1171, BY FOUR FOR LT /1/2 G1 117/1/2 G2 117/1/2 G3 5 Line Reguation 1.25 Reference Votage vs Temperature 8 Feedback Bias Current vs Temperature REFERENCE VOLTAGE CHANGE (mv) T J = 15 C T J = 55 C T J = 25 C INPUT VOLTAGE (V) 117/1/2 G4 REFERENCE VOLTAGE (V) TEMPERATURE ( C) 117/1/2 G5 FEEDBACK BIAS CURRENT (na) TEMPERATURE ( C) 117/1/2 G6 SUPPLY CURRENT (μa) Suppy Current vs Suppy Votage (Shutdown Mode) Driver Current* vs Switch Current Suppy Current vs Input Votage* T J = 25 C T J = 25 C NOTE THAT THIS CURRENT DOES NOT INCLUDE DRIVER CURRENT, WHICH IS 12 A FUNCTION OF LOAD CURRENT AND = 5mV 1 DUTY CYCLE. 11 T J = 55 C 8 1 9% DUTY CYCLE 6 9 5% DUTY CYCLE 4 T J = 25 C 8 7 1% DUTY CYCLE = V 2 6 % DUTY CYCLE SUPPLY VOLTAGE (V) SWITCH CURRENT (A) INPUT VOLTAGE (V) 117/1/2 G9 117/1/2 G8 117/1/2 G7 * AVERAGE LT117 POWER SUPPLY CURRENT IS * UNDER VERY LOW OUTPUT CURRENT CONDITIONS, FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH DUTY CYCLE, THEN ADDING QUIESCENT CURRENT. 1% OR LESS fg DRIVER CURRENT (ma) SUPPLY CURRENT (ma)

7 TYPICAL PERFORMANCE CHARACTERISTICS LT117/LT1171/LT1172 SUPPLY CURRENT (μa) Shutdown Mode Suppy Current Error Ampifier Transconductance VC Pin Characteristics T J = 15 C 55 C T J 125 C PIN VOLTAGE (mv) 117/1/2 G1 TRANSCONDUCTANCE (μmho) 5 45 g m = I ( PIN) V ( PIN) TEMPERATURE ( C) 117/1/2 G11 PIN CURRENT (μa) V = 1.5V (CURRENT INTO PIN) T J = 25 C V =.8V (CURRENT OUT OF PIN) PIN VOLTAGE (V) 117/1/2 G12 IDLE SUPPLY CURRENT (ma) Ide Suppy Current vs Temperature Feedback Pin Camp Votage Switch Off Characteristics 11 1 =.6V V SUPPLY = 6V 6 V SUPPLY = 3V TEMPERATURE ( C) 117/1/2 G13 FEEDBACK VOLTAGE (mv) C 25 C 15 C FEEDBACK CURRENT (ma) 117/1/2 G14 SWITCH CURRENT (μa) V SUPPLY = 3V V SUPPLY = 15V V SUPPLY = 4V V SUPPLY = 55V SWITCH VOLTAGE (V) 117/1/2 G15 4 Shutdown Threshods Fyback Banking Time 23 Isoated Mode Fyback Reference Votage PIN VOLTAGE (mv) CURRENT (OUT OF PIN) VOLTAGE 1 1 VOLTAGE IS REDUCED UNTIL 5 REGULATOR CURRENT DROPS 5 BELOW 3μA TEMPERATURE ( C) 117/1/2 G PIN CURRENT (μa) TIME (μs) JUNCTION TEMPERATURE ( C) 117/1/2 G17 FLYBACK VOLTAGE (V) R = 5Ω R = 1k R = 1k TEMPERATURE ( C) 117/1/2 G fg 7

8 LT117/LT1171/LT1172 TYPICAL PERFORMANCE CHARACTERISTICS TRANSCONDUCTANCE (μmho) k Transconductance of Error Ampifier 1k 1k 1M FREQUENCY (Hz) g m 117/1/2 G M PHASE (DEG) FEEDBACK PIN VOLTAGE (mv) Norma/Fyback Mode Threshod on Feedback Pin FEEDBACK PIN VOLTAGE (AT THRESHOLD) FEEDBACK PIN CURRENT (AT THRESHOLD) TEMPERATURE ( C) 117/1/2 G2 FEEDBACK PIN CURRENT (μa) BLOCK DIAGRAM 16V SWITCH OUT 2.3V REG FLYBACK ERROR AMP LT1172 1kHz OSC LOGIC DRIVER 5A, 75V SWITCH MODE SELECT ANTI- SAT COMP ERROR AMP 1.24V REF SHUTDOWN CIRCUIT.15V CURRENT AMP GAIN 6.2Ω (.4Ω LT1171) (.16Ω LT1172).16Ω (LT117 AND LT1171 ONLY) E1 ALWAYS CONNECT E1 TO THE GROUND PIN ON MINIDIP, 8- AND 16-PIN SURFACE MOUNT PACKAGES. E1 AND E2 INTERNALLY TIED TO GROUND ON TO-3 AND TO-22 PACKAGES. E2 117/1/2 BD fg

9 OPERATION The LT117/LT1171/LT1172 are current mode switchers. This means that switch duty cyce is directy controed by switch current rather than by output votage. Referring to the bock diagram, the switch is turned on at the start of each osciator cyce. It is turned off when switch current reaches a predetermined eve. Contro of output votage is obtained by using the output of a votage sensing error ampifier to set current trip eve. This technique has severa advantages. First, it has immediate response to input votage variations, unike ordinary switchers which have notoriousy poor ine transient response. Second, it reduces the 9 phase shift at midfrequencies in the energy storage inductor. This greaty simpifies cosed oop frequency compensation under widey varying input votage or output oad conditions. Finay, it aows simpe puse-by-puse current imiting to provide maximum switch protection under output overoad or short conditions. A ow dropout interna reguator provides a 2.3V suppy for a interna circuitry on the LT117/LT1171/LT1172. This ow dropout design aows input votage to vary from 3V to 6V with virtuay no change in device performance. A 1kHz osciator is the basic cock for a interna timing. It turns on the output switch via the ogic and driver circuitry. Specia adaptive anti-sat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneousy to imit switch saturation. This minimizes driver dissipation and provides very rapid turnoff of the switch. A 1.2V bandgap reference biases the positive input of the error ampifier. The negative input is brought out for output votage sensing. This feedback pin has a second function; when pued ow with an externa resistor, it programs the LT117/LT1171/LT1172 to disconnect the main error ampifier output and connects the output of the fyback ampifier to the comparator input. The LT117/LT1171/LT1172 wi then reguate the vaue of the fyback puse with respect to the suppy votage.* This fyback puse is directy proportiona to output votage in the traditiona transformer couped fyback topoogy reguator. By reguating the ampitude of the fyback puse, the output votage can be reguated with no direct connection between input and output. The output is fuy foating up to the breakdown votage of the transformer windings. Mutipe foating outputs are easiy obtained with additiona windings. LT117/LT1171/LT1172 A specia deay network inside the LT117/ LT1171/LT1172 ignores the eakage inductance spike at the eading edge of the fyback puse to improve output reguation. The error signa deveoped at the comparator input is brought out externay. This pin ( ) has four different functions. It is used for frequency compensation, current imit adjustment, soft-starting, and tota reguator shutdown. During norma reguator operation this pin sits at a votage between.9v (ow output current) and 2.V (high output current). The error ampifiers are current output (g m ) types, so this votage can be externay camped for adjusting current imit. Likewise, a capacitor couped externa camp wi provide soft-start. Switch duty cyce goes to zero if the pin is pued to ground through a diode, pacing the LT117/LT1171/LT1172 in an ide mode. Puing the pin beow.15v causes tota reguator shutdown, with ony 5μA suppy current for shutdown circuitry biasing. See Appication Note 19 for fu appication detais. Extra Pins on the MiniDIP and Surface Mount Packages The 8- and 16-pin versions of the LT1172 have the emitters of the power transistor brought out separatey from the ground pin. This eiminates errors due to ground pin votage drops and aows the user to reduce switch current imit 2:1 by eaving the second emitter (E2) disconnected. The first emitter (E1) shoud aways be connected to the ground pin. Note that switch on resistance doubes when E2 is eft open, so efficiency wi suffer somewhat when switch currents exceed 3mA. Aso, note that chip dissipation wi actuay increase with E2 open during norma oad operation, even though dissipation in current imit mode wi decrease. See Therma Considerations next. Therma Considerations When Using the MiniDIP and SW Packages The ow suppy current and high switch efficiency of the LT1172 aow it to be used without a heat sink in most appications when the TO-22 or TO-3 package is seected. These packages are rated at 5 C/W and 35 C/W respectivey. The minidips, however, are rated at 1 C/W in ceramic (J) and 13 C/W in pastic (N). *See note under Bock Diagram fg 9

10 LT117/LT1171/LT1172 OPERATION Care shoud be taken for minidip appications to ensure that the worst case input votage and oad current conditions do not cause excessive die temperatures. The foowing formuas can be used as a rough guide to cacuate LT1172 power dissipation. For more detais, the reader is referred to Appication Note 19 (AN19), Efficiency Cacuations section. Average suppy current (incuding driver current) is: I IN 6mA I SW (.4 DC/4) I SW = switch current DC = switch duty cyce Switch power dissipation is given by: P SW = (I SW ) 2 (R SW )(DC) R SW = LT1172 switch on resistance (1Ω maximum) Tota power dissipation is the sum of suppy current times input votage pus switch power: P D(TOT) = (I IN )( ) P SW In a typica exampe, using a boost converter to generate 12V at.12a from a 5V input, duty cyce is approximatey 6%, and switch current is about.65a, yieding: I IN = 6mA.65(.4 DC/4) = 18mA P SW = (.65) 2 (1Ω)(.6) =.25W P D(TOT) = (5V)(.18A).25 =.34W Temperature rise in a pastic minidip woud be 13 C/W times.34w, or approximatey 44 C. The maximum ambient temperature woud be imited to 1 C (commercia temperature imit) minus 44 C, or 56 C. In most appications, fu oad current is used to cacuate die temperature. However, if overoad conditions must aso be accounted for, four approaches are possibe. First, if oss of reguated output is acceptabe under overoad conditions, the interna therma imit of the LT1172 wi protect the die in most appications by shutting off switch current. Therma imit is not a tested parameter, however, and shoud be considered ony for noncritica appications with temporary overoads. A second approach is to use the arger TO-22 (T) or TO-3 (K) package which, even without a heat sink, may imit die temperatures to safe eves under overoad conditions. In critica situations, heat sinking of these packages is required; especiay if overoad conditions must be toerated for extended periods of time. The third approach for ower current appications is to eave the second switch emitter (minidip ony) open. This increases switch on resistance by 2:1, but reduces switch current imit by 2:1 aso, resuting in a net 2:1 reduction in I 2 R switch dissipation under current imit conditions. The fourth approach is to camp the pin to a votage ess than its interna camp eve of 2V. The LT1172 switch current imit is zero at approximatey 1V on the pin and 2A at 2V on the pin. Peak switch current can be externay camped between these two eves with a diode. See AN19 for detais. LT117/LT1171/LT1172 Synchronizing The LT117/LT1171/LT1172 can be externay synchronized in the frequency range of 12kHz to 16kHz. This is accompished as shown in the accompanying figures. Synchronizing occurs when the pin is pued to ground with an externa transistor. To avoid disturbing the DC characteristics of the interna error ampifier, the width of the synchronizing puse shoud be under.3μs. sets the puse width at.2μs. The effect of a synchronizing puse on the LT117/LT1171/LT1172 ampifier offset can be cacuated from: KT q t S ΔV OS = ( )( f S ) I C I C KT = 26mV at 25 C q t C = puse width f S = puse frequency I C = source current ( 2μA) = operating votage (1V to 2V) = resistor used to set mid-frequency zero in frequency compensation network fg

11 OPERATION With t S =.2μs, f S = 15kHz, = 1.5V, and = 2k, offset votage shift is 3.8mV. This is not particuary bothersome, but note that high offsets coud resut if were reduced to a much ower vaue. Aso, the synchronizing LT117/LT1171/LT1172 transistor must sink higher currents with ow vaues of, so arger drives may have to be used. The transistor must be capabe of puing the pin to within 2mV of ground to ensure synchronizing. Synchronizing with Bipoar Transistor Synchronizing with MOS Transistor LT117 LT117 2N pF 2.2k 3k FROM 5V LOGIC VN2222* 1N k 1pF D2 1N4158 FROM 5V LOGIC 117/1/2 OP1 * SILICONIX OR EQUIVALENT 117/1/2 OP2 TYPICAL APPLICATIONS Fyback Converter L2 5μH OPTIONAL FILTER V SNUB CLAMP TURN-ON SPIKE C4* 1μF 2V TO 3V LT117 D3 25V 1W D2 MU1 N* = 1/3 1 N* C4 1μF 2μF V OUT 5V 6A 3.74k V V a c I b d V OUT V f I PRI N I PRI /N V PRIMARY FLYBACK VOLTAGE = OUT Vf N LT117 SWITCH VOLTAGE AREA a = AREA b TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY SECONDARY VOLTAGE AREA c = AREA d TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY PRIMARY CURRENT 1.5k.15μF 1.24k I PRI I PRI SECONDARY CURRENT LT117 SWITCH CURRENT *REQUIRED IF INPUT LEADS 2" t = (I PRI)(L L ) V SNUB SNUBBER DIODE CURRENT 117/1/2 TA fg 11

12 LT117/LT1171/LT1172 TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.) LCD Contrast Suppy OPTIONAL SHUTDOWN E2 VN2222 E1 5V* L1** 5μH LT1172 C4.47μF 1k 15k V BAT * 3V TO 2V 2k 1N914 C3.47μF 1μF TANTALUM D3 D2 V OUT 1V TO 26V *** 2μF TANTALUM D2, D3 = ER82.4 6mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED. * AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR V BAT IS EQUAL TO THE NEGATIVE OUTPUT 1V. WITH HIGHER BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 8% AT I OUT = 25mA.,, ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY V BAT /( ). ** FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT 6mA AT P OUT =.7Ω. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN.4Ω FOR HIGH EFFICIENCY. *** A 1Ω, 1μF TANTALUM OUTPUT FILTER. OUTPUT RIPPLE IS ABOUT 2mV P-P TO 4mV P-P WITH = 2μF TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE, OR ADD 117/1/2 TA4 Driving High Votage FET (for Off-Line Appications, See AN25) Externa Current Limit 1V TO 2V LT117 G D Q1 5Ω V X 2V LT /1/2 TA5 117/1/2 TA fg

13 LT117/LT1171/LT1172 TYPICAL APPLICATIONS (Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.) Negative-to-Positive Buck-Boost Converter Externa Current Limit OPTIONAL INPUT FILTER L3 C4* 1μF 2V REQUIRED IF INPUT LEADS 2" LT117 L1** 5μH 2.2k.22μF 1.24k L2 OPTIONAL OUTPUT FILTER 1μF * ** PULSE ENGINEERING 92114, COILTRONICS THIS CIRCUIT IS OFTEN USED TO CONVERT 48V TO 5V. TO GUARANTEE FULL SHORT-CIRCUIT PROTECTION, THE CURRENT LIMIT CIRCUIT SHOWN IN AN19, FIGURE 39, SHOULD BE ADDED WITH REDUCED TO 2pF. Q1 C3 V OUT 12V 2A 11.3k 117/1/2 TA7 Q1 1k 1pF R S NOTE THAT THE LT117 PIN IS NO LONGER COMMON TO. LT /1/2 TA8 Negative Buck Converter * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING COILTRONICS C3* 1μF LT117 L1** 5μH 1μF Q1 2N k R4 12k LOAD 5.2V 4.5A OPTIONAL INPUT FILTER L3 OPTIONAL OUTPUT FILTER C4 2μF 2V 1.24k 117/1/2 TA fg 13

14 LT117/LT1171/LT1172 TYPICAL APPLICATIONS D3 1N41 C4 1μF LT117 R5 47Ω, 1W 5k.1μF Positive-to-Negative Buck-Boost Converter 1.7k 1.24k L1** 5μH 1V TO 3V C5 1μF* D2 1N914 C3 2μF R4 47Ω * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114, COILTRONICS TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES BELOW 1V, CONNECT ANODE OF D3 TO, AND REMOVE R5. MAY BE REDUCED FOR LOWER OUTPUT CURRENTS. (5μF)(I OUT ). FOR 5V OUTPUTS, REDUCE TO 1.5k, INCREASE TO.3μF, AND REDUCE R6 TO 1Ω. 1μF R6 47Ω V OUT 12V 2A 117/1/2 TA1 High Efficiency Constant Current Charger INPUT VOLTAGE > V BAT 2V < 35V 2μF 35V 1N μF 35V TANTALUM LT1171 VC C3.47μF 1k C4.1μF V V LT16 25k I CHRG = * L2 REDUCES RIPPLE CURRENT INTO THE BATTERY BY ABOUT 2:1. IT MAY BE OMITTED IF DESIRED. R4 1k L1 1μH, 1A 1.244V R4 R5 L2* 1μH, 1A = 1A AS SHOWN RUN = V SHUTDOWN = 5V R6 78k R7 22k 2N394 R8 1k D2 MB4 R5.5Ω 1A C4 2μF 25V BATTERY 2V TO 25V 117/1/2 TA11 INPUT VOLTAGE 4.5V TO 2V Backight CCFL Suppy (see AN45 for detais) L2*** 1k 1N5818 L1** 3μH A 33pF 3kV LAMP Q1* 1μF TANT E2 E1 LT1172 2μF C6 1μF.2μF Q2* B 1N914 1k D2 1N914 56Ω 5k INTENSITY ADJUST * Q1,Q2 = BCP56 OR MPS65/561 COILTRONICS CTX /1/2 TA12 ** *** SUMIDA OR COILTRONICS A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY fg

15 TYPICAL APPLICATIONS Positive Buck Converter LT117/LT1171/LT1172 C3 2.2μF C5* 1μF D3 LT117 47Ω 1μF r * REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING COILTRONICS k 1.24k 1μF D2 1N914 L1** 5μH C4 1μF L2 4μH OPTIONAL OUTPUT FILTER C5 2μF R4 1Ω 5V, 4.5A 1mA MINIMUM 117/1/2 TA13 Negative Boost Reguator D2 C4* 47μF 15V L1 5μH LT117 * REQUIRED IF INPUT LEADS 2" 3.3k.22μF 27k 1.24k C3 1μF 1μF V OUT 28V, 1A R O (MINIMUM LOAD) 117/1/2 TA14 Driving High Votage NPN D2 ** * Q1 LT117 * SETS I B (ON) ** SETS I B (OFF) 117/1/2 TA fg 15

16 LT117/LT1171/LT1172 TYPICAL APPLICATIONS Forward Converter R4 D3 T1 1 M N D2 L1 25μH 2μF 3.74k V OUT 5V, 6A 2V TO 3V LT117 D4 C3 Q1 R6 33Ω C4 R5 1Ω 1.24k 117/1/2 TA16 High Efficiency 5V Buck Converter 33μF 35V C6.2μF C4.1μF MB3p 68Ω LT117 C5.3μF DIODE C3 4.7μF TANT V D2 1N4148 L1 5μH *.13Ω 1μH 3A 1μF 16V 39μF 16V OPTIONAL OUTPUT FILTER V OUT 5V 3A** MODE LOGIC 22pF <.3V = NORMAL MODE >2.5V = SHUTDOWN OPEN = BURST MODE MODE LT1432 V LIM V OUT * IS MADE FROM PC BOARD COPPER TRACES. ** MAXIMUM CURRENT IS DETERMINED BY THE CHOICE OF LT17 FAMILY. SEE APPLICATION SECTION. 117/1/2 TA fg

17 PACKAGE DESCRIPTION J8 Package 8-Lead CERDIP (Narrow.3 Inch, Hermetic) (Reference LTC DWG # ) LT117/LT1171/LT ( ) FULL LEAD OPTION.3 BSC (7.62 BSC) CORNER LEADS OPTION (4 PLCS) ( ) HALF LEAD OPTION.5 (.127) MIN.25 (.635) RAD TYP.45 (1.287) MAX ( ).2 (5.8) MAX.15.6 ( ).8.18 ( ) 15 NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS ( ) (.36.66).1 (2.54) BSC MIN J8 81 K Package 4-Lead TO-3 Meta Can (Reference LTC DWG # ) ( ) ( ) ( ) ( ).47 TP P.C.D ( ) ( ) DIA 2 PLC ( ) ( ) R ( ) ( ) R K4(TO-3) 81 (OBSOLETE PACKAGE) 11712fg 17

18 LT117/LT1171/LT1172 PACKAGE DESCRIPTION N8 Package 8-Lead PDIP (Narrow.3 Inch) (Reference LTC DWG # ).4* (1.16) MAX ±.15* (6.477 ±.381) ( ) ( ).13 ±.5 (3.32 ±.127).8.15 ( ) ( ).65 (1.651) TYP.1 (2.54) BSC NOTE: INCHES 1. DIMENSIONS ARE MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED.1 INCH (.254mm).12 (3.48) MIN.18 ±.3 (.457 ±.76).2 (.58) MIN N fg

19 PACKAGE DESCRIPTION Q Package 5-Lead Pastic DD Pak (Reference LTC DWG # ) LT117/LT1171/LT (6.52).6 (1.524).6 (1.524) TYP ( ) 15 TYP ( ) ( ).6 (1.524).183 (4.648) ( ).59 (1.499) TYP ( ).3 (7.62).75 (1.95) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK ( ).67 (1.72) BSC ( ) TYP ( ) ( ).5 ±.12 (1.27 ±.35) Q(DD5) RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS 11712fg 19

20 LT117/LT1171/LT1172 PACKAGE DESCRIPTION S8 Package 8-Lead Pastic Sma Outine (Narrow.15 Inch) (Reference LTC DWG # ).5 BSC.45 ± ( ) NOTE MIN.16 ± ( ) ( ) NOTE 3.3 ±.5 TYP RECOMMENDED SOLDER PAD LAYOUT ( ).1.2 ( ) 45 8 TYP ( ).4.1 ( ).16.5 ( ) NOTE: INCHES 1. DIMENSIONS IN (MILLIMETERS) ( ) TYP 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED.6" (.15mm).5 (1.27) BSC SO fg

21 PACKAGE DESCRIPTION SW Package 16-Lead Pastic Sma Outine (Wide.3 Inch) (Reference LTC DWG # ) LT117/LT1171/LT ±.5 TYP N.5 BSC.45 ± ( ) NOTE N.42 MIN.325 ±.5 NOTE ( ) N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT (.127) RAD MIN ( ) NOTE ( ) 8 TYP ( ) ( ) (1.27) ( ) NOTE 3 BSC ( ) ( ) TYP NOTE: INCHES 1. DIMENSIONS IN (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS 4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED.6" (.15mm).4.12 (.12.35) S16 (WIDE) fg 21

22 LT117/LT1171/LT1172 PACKAGE DESCRIPTION T Package 5-Lead Pastic TO-22 (Standard) (Reference LTC DWG # ) ( ) ( ) DIA ( ) ( ) ( ).46.5 ( ) ( ) ( ).62 (15.75) TYP ( ) ( ) SEATING PLANE ( ) ( ) * ( ) BSC.67 (1.7) ( ) ( ) ( ) * MEASURED AT THE SEATING PLANE T5 (TO-22) fg

23 REVISION HISTORY (Revision history begins at Rev G) LT117/LT1171/LT1172 REV DATE DESCRIPTION PAGE NUMBER G 3/1 Updated to Reactivate LT1172M from Obsoeted Parts List 2 Information furnished by Technoogy Corporation is beieved to be accurate and reiabe. However, no responsibiity is assumed for its use. Technoogy Corporation makes no representation that the interconnection of its circuits as described herein wi not infringe on existing patent rights fg 23

24 LT117/LT1171/LT1172 TYPICAL APPLICATION Positive Current Boosted Buck Converter 28V 47Ω 2W C3.47μF R6 47Ω D2 C6.2μF 1: N C5* 1μF LT117 68Ω.33μF R7 1k C4.1μF 6 4 2pF 7 LM k R4 1.24k N.25 R5 5k 5k V OUT 5V, 1A 5μF * REQUIRED IF INPUT LEADS 2" 117/1/2 TA18 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT17/LT171/LT172 5A/2.5A/1.25A High Efficiency Switching Reguators 4kHz, to 6V, to 75V LT174/LT A/2A Step-Down Switching Reguators 1kHz, Aso for Positive-to-Negative Conversion LT182 1A, High Votage, High Efficiency Switching Reguator to 75V, to 1V, Teecom LT1268/LT1268B 7.5A, 15kHz Switching Reguators to 3V, to 6V LT1269/LT1271 4A High Efficiency Switching Reguators 1kHz/6kHz, to 3V, to 6V LT127/LT127A 8A and 1A High Efficiency Switching Reguators 6kHz, to 3V, to 6V LT137 5kHz High Efficiency 6A Switching Reguator High Power Boost, Fyback, SEPIC LT1371 5kHz High Efficiency 3A Switching Reguator Good for Boost, Fyback, Inverting, SEPIC LT1372/LT1377 5kHz and 1MHz High Efficiency 1.5A Switching Reguators Directy Reguates ±V OUT LT kHz Low Suppy Current High Efficiency 1.5A Switching Reguator Low 1mA Quiescent Current LT1374 4A, 5kHz Step-Down Switching Reguator Synchronizabe, to 25V LT1375/LT A, 5kHz Step-Down Switching Reguators Up to 1.25A Out from an SO-8 LT1425 Isoated Fyback Switching Reguator 6W Output, ±5% Reguation, No Optocouper Needed LT157 5kHz Monoithic Buck Mode Switching Reguator 1.5A Switch, Good for 5V to 3.3V LT1533 Utraow Noise 1A Switching Reguator Push-Pu, <1μV P-P Output Noise 24 Linear Technoogy Corporation 11712fg LT 41 REV G PRINTED IN USA 163 McCarthy Bvd., Mipitas, CA (48) FAX: (48) LINEAR TECHNOLOGY CORPORATION 1991