FEATURES APPLICATIONS TYPICAL APPLICATION

Size: px

Start display at page:

Download "FEATURES APPLICATIONS TYPICAL APPLICATION"

Martha Burke
6 years ago
Views:

FEATURES n Reguates Whie Sourcing or Sinking Current n Provides Termination for up to 27 SCSI Lines n μa Quiescent Current n Utraow Power Shutdown Mode n Current Limit and Therma Shutdown Protection

1 FEATURES n Reguates Whie Sourcing or Sinking Current n Provides Termination for up to 27 SCSI Lines n μa Quiescent Current n Utraow Power Shutdown Mode n Current Limit and Therma Shutdown Protection n Stabe for Any C LOAD.22μF n Fast Setting Time n Dropout otage APPLICATIONS n Active Negation SCSI Terminations n Computers n Disk Drives n CD-ROM n Suppy Spitter L, LT, LTC and LTM are registered trademarks of Linear Technoogy Corporation. A other trademarks are the property of their respective owners. LT8/LT8-2. Low I Q, Low Dropout, 8mA, Source and Sink Reguators Adjustabe and Fixed 2., 2.8, Output DESCRIPTION The LT 8 famiy of ow dropout reguators has the unique capabiity of maintaining output reguation whie sourcing or sinking oad current. The 2.8 output votage reguator is idea for use as a Bouay termination of up to 27 SCSI data ines. The reguator maintains reguation whie both sourcing and sinking current, enabing the use of active negation drivers for improved noise immunity on the data ines. Reguation of output votage is maintained for TERMPWR votages as ow as 4.. When unoaded, quiescent suppy current is a ow μa, aowing continuous connection to the TERMPWR ines. An utraow power shutdown mode is aso avaiabe on the SO-8 version. In Shutdown the output is high impedance and suppy current drops to ess than μa. Current imits in both sourcing and sinking modes, pus on-chip therma shutdown make the circuit toerant of output faut conditions. The LT8 is avaiabe in 3-ead SOT-223 and 8-ead SO packages. TYPICAL APPLICATION Load Transient Response LT μF CERAMIC I LOAD 8mA 8 TA I LOAD ma 4mA 8 TA2

2 LT8/LT8-2./ ABSOLUTE MAXIMUM RATGS (Note ) Suppy otage ( CC )... Input otage (Enabe)....2 to 7 Output otage....2 to CC +. Short-Circuit Duration... Indefinite Operating Temperature Range... C to 7 C Storage Temperature Range... C to C Lead Temperature (Sodering, sec)... 3 C P CONFIGURATION TOP IEW TOP IEW FRONT IEW 8 8 EN 3 NC EN TAB IS 2 FB 4 4 NC S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 2 C, θ JA = C/W S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 2 C, θ JA = C/W ST PACKAGE 3-LEAD PLASTIC SOT-223 T JMAX = 2 C, θ JC = C/W ORDER FORMATION LEAD FREE FISH TAPE AND REEL PART MARKG PACKAGE DESCRIPTION TEMPERATURE RANGE LT8CS8#PBF LT8CS8#TRPBF 8 8-Lead Pastic SO C to 7 C LT8CS8-2.#PBF LT8CS8-2.#TRPBF 82 8-Lead Pastic SO C to 7 C LT8CS8-2.8#PBF LT8CS8-2.8#TRPBF Lead Pastic SO C to 7 C LT8CS8-#PBF LT8CS8-#TRPBF 8 8-Lead Pastic SO C to 7 C LT8CST-2.#PBF LT8CST-2.#TRPBF 82 3-Lead Pastic SOT-223 C to 7 C LT8CST-2.8#PBF LT8CST-2.8#TRPBF Lead Pastic SOT-223 C to 7 C LT8CST-#PBF LT8CST-#TRPBF 8 3-Lead Pastic SOT-223 C to 7 C LEAD BASED FISH TAPE AND REEL PART MARKG* PACKAGE DESCRIPTION TEMPERATURE RANGE LT8CS8 LT8CS8#TR 8 8-Lead Pastic SO C to 7 C LT8CS8-2. LT8CS8-2.#TR 82 8-Lead Pastic SO C to 7 C LT8CS8-2.8 LT8CS8-2.8#TR Lead Pastic SO C to 7 C LT8CS8- LT8CS8-#TR 8 8-Lead Pastic SO C to 7 C LT8CST-2. LT8CST-2.#TR 82 3-Lead Pastic SOT-223 C to 7 C LT8CST-2.8 LT8CST-2.8#TR Lead Pastic SOT-223 C to 7 C LT8CST- LT8CST-#TR 8 3-Lead Pastic SOT-223 C to 7 C Consut LTC Marketing for parts specified with wider operating temperature ranges. For more information on ead free part marking, go to: For more information on tape and ree specifi cations, go to: 2

3 ELECTRICAL CHARACTERISTICS LT8/LT8-2. The denotes the specifi cations which appy over the fu operating temperature range, otherwise specifi cations are at T A = 2 C. (Note 2) PARAMETER CONDITIONS M TYP MAX UNITS Quiescent Current ( ) EN =. ma Quiescent Current in Shutdown ( ) EN = μa Enabe Input Threshods Input Low Leve.4.4 Input High Leve.4 2 Enabe Input Current EN 2 μa Feedback otage Output otage Line Reguation (Note 4) Load Reguation (Note 4) Dropout otage (Note ) No Load (2 C) (LT8) A Operating Conditions (Note 3) No Load (2 C) (LT8-2.) A Operating Conditions (Note 3) No Load (2 C) (LT8-2.8) A Operating Conditions (Note 3) No Load (2 C) (LT8-) A Operating Conditions (Note 3) I L = ma, 4.2 (LT8) I L = ma, 4.2 (LT8-2.) I L = ma, 4.7 (LT8-2.8) I L = ma,. (LT8-) ma I L 8mA (LT8) 4mA I L ma ma I L 8mA (LT8-2.) 4mA I L ma ma I L 8mA (LT8-2.8) 4mA I L ma ma I L 8mA (LT8-) 4mA I L ma I L = ma I L = 8mA FB Pin Bias Current LT8.3 μa Minimum Output otage LT8 2. Rippe Rejection f RIPPLE = 2Hz, = 2 db RIPPLE =. P-P Load Transient Setting Time, Δ = % Output Short-Circuit Current ma I L 8mA, C LOAD = 4mA I L ma, C LOAD = =, Sourcing =, Sinking Therma Shutdown Junction Temperature No Load 7 C Enabe Turn-On Deay No Load μs m m m m m m m m m m m m μs μs ma ma Note : 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: Uness otherwide specified, testing done at CC = (LT8-2., LT8-2.8) or CC = 7 (LT8-). EN = CC. Output C LOAD =, I LOAD =. Note 3: A operating conditions incude the combined effects of oad current, input votage and temperature over each parameter s fu range. Note 4: Load and ine reguation are tested at a constant junction temperature by ow duty cyce puse testing. Note : Dropout votage is defi ned as the minimum input to output votage measured whie sourcing the specifi ed current. 3

4 LT8/LT8-2./ TYPICAL PERFORMANCE CHARACTERISTICS DROP OLTAGE () Dropout otage vs Output Current Rippe Rejection vs Frequency Rippe Rejection vs Frequency T J = 2 C T J = 7 C T J = 2 C PUT CURRENT (ma) 8 G RIPPLE REJECTION (db) mA NO LOAD ma SOURCG CURRENT k k k FREQUENCY (Hz) 8 G2 RIPPLE REJECTION (db) SKG CURRENT 4mA NO LOAD ma k k k FREQUENCY (Hz) 8 G3 Z (Ω)... 2 Output Impedance vs Frequency Feedback Current vs Temperature Rippe Rejection vs Load Current ma SOURCE NO CURRENT ma SOURCE ma SK ma SK 3 4 FREQUENCY (Hz) 8 G4 CURRENT (na) TEMPERATURE ( C) 8 G RIPPLE REJECTION (db) C = C LOAD = LOAD CURRENT (ma) 8 8 G 2 7 Input Current vs Output Sink Current 8 7 Ground Pin Current vs Output Source Current PUT CURRENT (μa) 2 7 GROUND P CURRENT (μa) PUT SK CURRENT (ma) PUT SOURCG CURRENT (ma) 8 8 G7 8 G8 4

5 P FUNCTIONS : Input Suppy Pin. This pin shoud be decouped with a or arger ow ESR capacitor. The two pins on the SO-8 package must be directy connected on the printed circuit board to prevent votage drops between the two inputs. When used as a SCSI active termination, connects to term power. When used as a suppy spitter, is aso the positive suppy output. : Ground Pin. The mutipe pins on the SO-8 package are internay connected, but owest oad reguation errors wi resut if these pins are tighty connected on the printed circuit board. This wi aso aid heat dissipation at high power eves. EN: TTL/CMOS Logic Input. A high eve aows norma operation. A ow eve reduces suppy current to zero. This pin is internay connected to on 3-ead ST packaged devices. LT8/LT8-2. : Reguated Output otage. Output can source or sink current. Current imit for sourcing and sinking current is provided to protect the device from faut conditons. The output must have a ow ESR output fiter capacitor. C.22μF to guarantee stabiity. A. ceramic capacitor may be needed in parae with C if the ESR of the main C is too high. FB: Feedback Pin. The feedback pin is used to program the output votage of the adjustabe S8 part. The output votage range that can be achieved is 2. to.. The output votage is determined by the seection of feedback resistors defined by the foowing formua: = FB ( + R /R 2 ) + I FB R LT8 LT8 Adjustabe R ( ) R = FB + + I FB R R 2 EN FB R 2 8 TA OPERATION Output Capacitor The LT8 famiy of votage reguators require an output capacitor for stabiity. The reguators are stabe with output capacitors arger than.2μf. Load transient response is very sensitive to output capacitor vaue and dieectric choice. Low ESR ceramic capacitors are the best choice for fast setting to oad transients. Output capacitors between.2μf and give good performance in most appications. Larger tantaum output capacitors may be used to reduce oad transient ampitudes. Larger capacitors shoud be paraeed with a. ceramic capacitor to maintain quick setting time performance and to insure stabiity of the reguator contro oop. Capacitors arger than may be safey used with the reguators, but itte transient setting performance improvement resuts from their use. Worst case transient response of the LT8 reguators occurs at zero output current. In order to obtain the fastest transient setting performance, the reguator output may be preoaded with a sma current. The preoad current reduces the reguator output impedance, reducing output votage setting time. Therma Considerations The LT8 reguators are packaged in pastic SOT-223 and fused ead S8 packages. These sma footprint packages are unabe to convectivey dissipate the heat generated when the reguator is operating at high current eves. In order to contro die operating temperatures, the PC board ayout shoud aow for maximum possibe copper area at the ground pins of the LT8. The ground pins and the tab on the SOT-223 package are eectricay and thermay

6 LT8/LT8-2./ OPERATION connected to the die substrate. Tabe shows measured therma resistance from junction to ambient for the LT8 connected to various sized PC board ground panes. The power dissipated in the LT8 varies with input votage and oading. When the reguator is sourcing current the power which must be dissipated by the package is: P D = ( ) I LOAD When the reguator is sinking oad current, power dissipation is neary independent of and can be cacuated as: P D = I LOAD Heat sinking to the IC package must consider the worst case power dissipation which may occur. Tabe. Measured Therma Resistance from Junction to Ambient for the LT8 S8 Package SOT-223 Free Air Sq Inch Copper 2 C/W C/W 9 C/W 3 C/W 4 Sq Inch Copper 3 C/W 38 C/W TYPICAL APPLICATIONS SCSI Active Terminator TERMPWR Ω Ω + LT μF Ω Ω Ω 27 LES 8 TA3 Power Suppy Spitter LT8-2. ANALOG COMMON 2. 8 TA4

7 PACKAGE DESCRIPTION (.3.7).4.24 (2.9 3.) ST Package 3-Lead Pastic SOT-223 (Reference LTC DWG # -8-3) LT8/LT MAX.29 MAX (.7 7.3).3.4 ( ).39 MAX.248 BSC.9 MAX.9 (2.3) BSC.33.4 (.84.4).8 MAX.9 BSC RECOMMENDED SOLDER PAD LAY.7 (.8) MAX MAX..4 (.2.3) (..84).8 (4.) BSC.2 (.3) M.8.4 (.23.) ST3 (SOT-233) 2 S8 Package 8-Lead Pastic Sma Outine (Narrow.) (Reference LTC DWG # -8-). BSC.4 ± (4.8.4) NOTE M. ± (.79.97)..7 ( ) NOTE 3.3 ±. TYP RECOMMENDED SOLDER PAD LAY (.23.24)..2 (.24.8) 4 8 TYP.3.9 (.34.72).4. (..24) (.4.27) (.3.483) NOTE: CHES TYP. DIMENSIONS (MILLIMETERS) 2. DRAWG NOT TO SCALE 3. THESE DIMENSIONS DO NOT CLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED." (.mm). (.27) BSC Information furnished by Linear Technoogy Corporation is beieved to be accurate and reiabe. However, no responsibiity is assumed for its use. Linear Technoogy Corporation makes no representation that the interconnection of its circuits as described herein wi not infringe on existing patent rights. SO8 33 7

8 LT8/LT8-2./ TYPICAL APPLICATION ariabe 2. to. Reguator with DIgita Contro 2 EN LT8 FB R 3.3k R 2.9k..22μF CC D DAC LTC27 CLK μp R 3.9k REF LOAD 8 TA =.22 R R + DAC R 2 R 3 R 2 ( ) RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT29 7mA, Micropower, LDO : 4.2 to 3, (M) = 3.8, DO =.4, I Q = μa, I SD = μa; DD, SOT-223, S8, TO22- and TSSOP2 Packages LT2 2mA/MHz Current Feedback Ampifi er High Output Current Drive Capabiity, Can Sink/Source LT2.A, 3MHz Current Feedback Ampifer High Output Current Drive Capabiity, Can Sink/Source LT73 ma, Low Noise Micropower, LDO :.8 to 2, (M) =.22, DO =.3, I Q = 3μA, I SD = < μa, Low Noise < 2μ RMS, S8 Package LT74/ LT74A 3A, Low Noise, Fast Transient Response, LDO : 2.7 to 2, (M) =.2, DO =.34, I Q = ma, I SD = < μa, Low Noise < 4μ RMS, A ersion Stabe with Ceramic Capacitors, DD and TO22- Packages LTC844 ma, ery Low Drop-Out LDO :. to., (M) =.2, DO =.8, I Q = 3μA, I SD = < μa, Low Noise < μ RMS, ThinSOT Package LT92 3mA, Low Noise Micropower, LDO :.8 to 2, (M) =.22, DO =.27, I Q = 3μA, I SD = < μa, Low Noise < 2μ RMS, MS8 Package LT93/ LT93A LT32 LT324 LT328 LT38/ LT38-.A, Low Noise, Fast Transient Response, LDO ma, Low otage DO, (M) =.9, LDO Dua, ma/ma, Low Noise Micropower, LDO Dua, ma/ma, Low Noise Micropower, LDO with Independent Inputs.A Paraeabe, Low Noise, Low Dropout Linear Reguator LT38 ma, Paraeabe Low Noise Low Dropout Linear Reguator ThinSOT is a trademark of Linear Technoogy Corporation : 2. to 2, (M) =.2, DO =.34, I Q = ma, I SD = < μa, Low Noise < 4μ RMS, A ersion Stabe with Ceramic Capacitors; DD, TO22-, SOT-223 and S8 Packages :.9 to, (M) =.2, DO =., I Q = 2μA, I SD = 3μA, DFN and S8 Packages :.8 to 2, (M) =.22, DO =.3, I Q = μa, I SD = < μa, DFN and TSSOP Packages :.8 to 2, (M) =.22, DO =.3, I Q = 3μA, I SD = < μa, Low Noise < 2μ RMS, DFN and TSSOP Packages 3m Dropout otage (2-Suppy Operation), Low Noise: 4μ RMS, :.2 to 3, : to 3.7, Current-Based Reference with -Resistor Set; Directy Paraeabe (No Op Amp Required), Stabe with Ceramic Caps, TO-22, SOT-223, MSOP and 3mm 3mm DFN Packages; LT38- ersion Has Integrated Interna Baast Resistor 27m Dropout otage (2 Suppy Operation), Low Noise: 4μ RMS, :.2 to 3, : to 3.7, Current Reference, MSOP-8 and 2mm 3mm DFN- Packages 8 LT 29 RE D PRTED USA Linear Technoogy Corporation 3 McCarthy Bvd., Mipitas, CA (48) FAX: (48) LEAR TECHNOLOGY CORPORATION 99

LT1176/LT Step-Down Switching Regulator FEATURES APPLICATIONS DESCRIPTION TYPICAL APPLICATION

LT1176/LT Step-Down Switching Regulator FEATURES APPLICATIONS DESCRIPTION TYPICAL APPLICATION Step-Down Switching Reguator FEATURES n 1.2A Onboard Switch n 100kHz Switching Frequency n Exceent Dynamic Behavior n DIP and Surface Mount Packages n Ony 8mA Quiescent Current n Preset 5 Output Avaiabe