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FEATRES Regulates While Sourcing or Sinking Current Provides Termination for up to 27 SCSI Lines 6µA Quiescent Current ltralow Power Shutdown Mode Current Limit and Thermal Shutdown Protection Stable for Any C LOAD.22µF Fast Settling Time V Dropout Voltage APPLICATIO S Active Negation SCSI Terminations Computers Disk Drives CD-ROM Supply Splitter LT8/LT8-2.5 Low I Q, Low Dropout, 8mA, Source and Sink Regulators Adjustable and Fixed 2.5V, 2.85V, 5V Output DESCRIPTIO The LT 8 family of low dropout regulators has the unique capability of maintaining output regulation while sourcing or sinking load current. The 2.85V output voltage regulator is ideal for use as a Boulay termination of up to 27 SCSI data lines. The regulator maintains regulation while both sourcing and sinking current, enabling the use of active negation drivers for improved noise immunity on the data lines. Regulation of output voltage is maintained for TERMPWR voltages as low as 4.V. When unloaded, quiescent supply current is a low 6µA, allowing continuous connection to the TERMPWR lines. An ultralow power shutdown mode is also available on the SO-8 version. In Shutdown the output is high impedance and supply current drops to less than µa. Current limits in both sourcing and sinking modes, plus on-chip thermal shutdown make the circuit tolerant of output fault conditions. The LT8 is available in 3-lead SOT-223 and 8-lead SO packages., LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO Load Transient Response.2V LT8-2.85 OT V OT V.2V 5V 2.2µF CERAMIC I LOAD 8mA 8 TA I LOAD ma 4mA 8 TA2.tif

LT8/LT8-2.5 ABSOLTE AXI RATI GS W W W Supply Voltage (V CC )... 5V Input Voltage (Enable)....2V to 7V Output Voltage....2V to V CC +.5V Short-Circuit Duration... Indefinite PACKAGE DESCRIPTIO (Note ) Operating Temperature Range... C to 7 C Storage Temperature Range... 65 C to 5 C Lead Temperature (Soldering, sec)... 3 C TOP VIEW TOP VIEW FRONT VIEW 8 8 EN 3 NC EN 2 3 7 6 OT OT 2 3 7 6 TAB IS 2 FB 4 5 4 5 NC OT S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 25 C, θ JC = 5 C/W S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 25 C, θ JC = 5 C/W ST PACKAGE 3-LEAD PLASTIC SOT-223 T JMAX = 25 C, θ JC = 5 C/W ORDER PART NMBER LT8CS8 S8 PART MARKG 8 ORDER PART NMBER LT8CS8-2.5 LT8CS8-2.85 LT8CS8-5 S8 PART MARKG 825 828 85 ORDER PART NMBER LT8CST-2.5 LT8CST-2.85 LT8CST-5 ST PART MARKG 825 828 85 Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are at T A = 25 C. (Note 2) PARAMETER CONDITIONS M TYP MAX NITS Quiescent Current (V ) V EN = 5V.6 ma Quiescent Current in Shutdown (V ) V EN = V µa Enable Input Thresholds Input Low Level.4.4 V Input High Level.4 2 V Enable Input Current V V EN 5V 25 µa Feedback Voltage LT8 No Load (25 C).23.225.237 V All Operating Conditions (Note 3).2.225.25 V Output Voltage LT8-2.5 No Load (25 C) 2.47 2.5 2.53 V All Operating Conditions (Note 3) 2.45 2.5 2.55 V LT8-2.85 No Load (25 C) 2.82 2.85 2.88 V All Operating Conditions (Note 3) 2.79 2.85 2.9 V LT8-5 No Load (25 C) 4.95 5 5.5 V All Operating Conditions (Note 3) 4.9 5 5. V 2

LT8/LT8-2.5 ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are at T A = 25 C. (Note 2) PARAMETER CONDITIONS M TYP MAX NITS Line Regulation (Note 4) LT8 I L = ma, 4.2V V 5V 6 mv LT8-2.5 I L = ma, 4.2V V 5V 6 mv LT8-2.85 I L = ma, 4.75V V 5V 6 mv LT8-5 I L = ma, 6.5V V 5V mv Load Regulation (Note 4) LT8 ma I L 8mA 6 mv 4mA I L ma 6 mv LT8-2.5 ma I L 8mA 2 mv 4mA I L ma 2 mv LT8-2.85 ma I L 8mA 2 mv 4mA I L ma 2 mv LT8-5 ma I L 8mA 25 mv 4mA I L ma 25 mv Dropout Voltage (Note 5) I L = ma.85. V I L = 8mA.3 V FB Pin Bias Current LT8.35 µa Minimum Output Voltage LT8 2. V Ripple Rejection f RIPPLE = 2Hz, V V OT = 2V 6 8 db V RIPPLE =.5V P-P Load Transient Settling Time, ma I L 8mA, C LOAD = 5 µs V = % 4mA I L ma, C LOAD = 5 µs Output Short-Circuit Current I SC + V OT = V 8 2 ma I SC V OT = V 7 4 ma Thermal Shutdown Junction Temperature No Load 7 C Enable Turn-On Delay No Load 5 µs Note : Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: nless otherwide specified, testing done at V CC = 5V (LT8-2.5, LT8-2.85) or V CC = 7V (LT8-5). V EN = V CC. Output C LOAD =, I LOAD =. Note 3: All operating conditions include the combined effects of load current, input voltage and temperature over each parameter s full range. Note 4: Load and line regulation are tested at a constant junction temperature by low duty cycle pulse testing. Note 5: Dropout voltage is defined as the minimum input to output voltage measured while sourcing the specified current. 3

LT8/LT8-2.5 TYPICAL PERFORMANCE CHARACTERISTICS W Dropout Voltage vs Output Current Ripple Rejection vs Frequency Ripple Rejection vs Frequency.4 8 8 DROPOT VOLTAGE.2.8.6.4 T J = 25 C T J = 75 C T J = 25 C RIPPLE REJECTION (db) 6 4 2 8mA ma NO LOAD RIPPLE REJECTION (db) 6 4 2 4mA ma NO LOAD.2 2 4 6 8 OTPT CRRENT (ma) SORCG CRRENT k k k FREQENCY (Hz) SKG CRRENT k k k FREQENCY (Hz) 8 G 8 G2 8 G3 Z OT (ma).. Output Impedance vs Frequency ma SORCE NO CRRENT ma SORCE ma SK CRRENT (na) 45 4 35 3 25 2 5 Feedback Current vs Temperature RIPPLE REJECTION (db) Ripple Rejection vs Load Current 8 C = C LOAD = 6 4 2 ma SK 5. 2 3 4 5 6 FREQENCY (Hz) 55 35 5 5 25 45 65 85 5 25 TEMP 4 2 2 4 LOAD CRRENT (ma) 6 8 8 G4 8 G5 8 G6 2 75 Input Current vs Output Sink Current 8 7 Ground Pin Current vs Output Source Current PT CRRENT (µa) 5 25 75 5 GROND P CRRENT (µa) 6 5 4 3 2 25 5 5 2 25 3 35 OTPT SK CRRENT (ma) 4 2 4 6 OTPT SORCG CRRENT (ma) 8 8 G7 8 G8 4

OPERATIO P FNCTIONS : Input Supply Pin. This pin should be decoupled with a or larger low ESR capacitor. The two pins on the SO-8 package must be directly connected on the printed circuit board to prevent voltage drops between the two inputs. When used as a SCSI active termination, connects to term power. When used as a supply splitter, is also the positive supply output. : Ground Pin. The multiple pins on the SO-8 package are internally connected, but lowest load regulation errors will result if these pins are tightly connected on the printed circuit board. This will also aid heat dissipation at high power levels. EN: TTL/CMOS Logic Input. A high level allows normal operation. A low level reduces supply current to zero. This pin is internally connected to V on 3-lead ST packaged devices. LT8/LT8-2.5 OT: Regulated Output Voltage. Output can source or sink current. Current limit for sourcing and sinking current is provided to protect the device from fault conditons. The output must have a low ESR output filter capacitor. C OT.22µF to guarantee stability. A. ceramic capacitor may be needed in parallel with C OT if the ESR of the main C OT is too high. FB: Feedback Pin. The feedback pin is used to program the output voltage of the adjustable S8 part. The output voltage range that can be achieved is 2.V to 6.5V. The output voltage is determined by the selection of feedback resistors defined by the following formula: V OT = V FB ( + R /R 2 ) + I FB R V LT8 LT8 Adjustable OT R ( ) R V OT = V FB + + I FB R R 2 EN FB R 2 8 TA6 Output Capacitor The LT8 family of voltage regulators require an output capacitor for stability. The regulators are stable with output capacitors larger than.2µf. Load transient response is very sensitive to output capacitor value and dielectric choice. Low ESR ceramic capacitors are the best choice for fast settling to load transients. Output capacitors between.2µf and give good performance in most applications. Larger tantalum output capacitors may be used to reduce load transient amplitudes. Larger capacitors should be paralleled with a. ceramic capacitor to maintain quick settling time performance and to insure stability of the regulator control loop. Capacitors larger than may be safely used with the regulators, but little transient settling performance improvement results from their use. Worst case transient response of the LT8 regulators occurs at zero output current. In order to obtain the fastest transient settling performance, the regulator output may be preloaded with a small current. The preload current reduces the regulator output impedance, reducing output voltage settling time. Thermal Considerations The LT8 regulators are packaged in plastic SOT-223 and fused lead S8 packages. These small footprint packages are unable to convectively dissipate the heat generated when the regulator is operating at high current levels. In order to control die operating temperatures, the PC board layout should allow for maximum possible copper area at the ground pins of the LT8. The ground pins and the tab on the SOT-223 package are electrically and 5

OPERATIO LT8/LT8-2.5 thermally connected to the die substrate. Table shows measured thermal resistance from junction to ambient for the LT8 connected to various sized PC board ground planes. The power dissipated in the LT8 varies with input voltage and loading. When the regulator is sourcing current the power which must be dissipated by the package is: P D = (V V OT ) I LOAD. When the regulator is sinking load current, power dissipation is nearly independent of V and can be calculated as: P D = V OT I LOAD. Heat sinking to the IC package must consider the worst case power dissipation which may occur. Table. Measured Thermal Resistance from Junction to Ambient for the LT8 S8 Package SOT-223 Free Air 2 C/W 95 C/W Sq Inch Copper 55 C/W 53 C/W 4 Sq Inch Copper 35 C/W 38 C/W TYPICAL APPLICATIO S SCSI Active Terminator + TERMPWR LT8-2.85 OT 5V 2.2µF Ω Ω Ω Ω Ω 27 LES 8 TA3 Power Supply Splitter V 5V 5V LT8-2.5 OT ANALOG COMMON 2.5V 8 TA4 6

PACKAGE DESCRIPTIO ST Package 3-Lead Plastic SOT-223 (LTC DWG # 5-8-63) LT8/LT8-2.5.248.264 (6.3 6.7).4.24 (2.9 3.5).59 MAX.29 MAX.264.287 (6.7 7.3).3.46 (3.3 3.7).39 MAX.248 BSC.59 MAX.95 (2.3) BSC.33.4 (.84.4).8 MAX.9 BSC RECOMMENDED SOLDER PAD LAYOT.7 (.8) MAX.24.33 (.6.84).8 (4.6) BSC.2 (.3) M 6 MAX S8 Package 8-Lead Plastic Small Outline (Narrow.5) (LTC DWG # 5-8-6).8.4 (.23.6) 6..4 (.25.36) ST3 (SOT-233) 52.5 BSC.45 ±.5.89.97 (4.8 5.4) NOTE 3 8 7 6 5.245 M.6 ±.5.228.244 (5.79 6.97).5.57 (3.8 3.988) NOTE 3.3 ±.5 TYP RECOMMENDED SOLDER PAD LAYOT 2 3 4.8. (.23.254)..2 (.254.58) 45 8 TYP.53.69 (.346.752).4. (..254).6.5.4.9 (.46.27) (.355.483) NOTE: CHES TYP. DIMENSIONS (MILLIMETERS) 2. DRAWG NOT TO SCALE 3. THESE DIMENSIONS DO NOT CLDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED.6" (.5mm).5 (.27) BSC Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. SO8 33 7

LT8/LT8-2.5 TYPICAL APPLICATIO Variable 2.V to 6.5V Regulator with Digital Control 2V EN OT LT8 FB R 3.3k R 2 6.9k. V OT.22µF V CC D V DAC V OT LTC257 CLK µp R 3 6.9k V REF LOAD 8 TA5 V OT =.225 R R + V DAC R 2 R 3 R 2 ( ) RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT5 Logic Controlled Regulator 5V, A Main Output Plus 35mA Auxilliary Output LT7 8mA Low Dropout Regulator Fixed 2.85V, 3.3V, 5V or Adjustable Outputs LT2A Micropower Regulator with Comparator and Shutdown 2µA Supply Current, 2.5V Reference Output LT2 Micropower Low Dropout Regulator with Shutdown Reverse Voltage and Reverse Current Protection 8 Linear Technology Corporation 63 McCarthy Blvd., Milpitas, CA 9535-747 (48) 432-9 FAX: (48) 434-57 www.linear.com LT/LWI 76 REV C PRTED SA LEAR TECHNOLOGY CORPORATION 995