 |
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
| Datasheet File OCR Text: |
| MC34268 SCSI-2 Active Terminator Regulator The MC34268 is a medium current, low dropout positive voltage regulator specifically designed for use in SCSI-2 active termination circuits. This device offers the circuit designer an economical solution for precision voltage regulation, while keeping power losses to a minimum. The regulator consists of a 1.0 V dropout composite PNP/NPN pass transistor, current limiting, and thermal limiting. These devices are packaged in the 8-pin SOP-8 and 3-pin DPAK surface mount power packages. Applications include active SCSI-2 terminators and post regulation of switching power supplies. * 2.85 V Output Voltage for SCSI-2 Active Termination SCSI-2 ACTIVE TERMINATOR REGULATOR SEMICONDUCTOR TECHNICAL DATA * * * * * * * 1.0 V Dropout Output Current in Excess of 800 mA Thermal Protection Short Circuit Protection Output Trimmed to 1.4% Tolerance No Minimum Load Required Space Saving DPAK and SOP-8 Surface Mount Power Packages 1 8 1 D SUFFIX PLASTIC PACKAGE CASE 751 (SOP-8) 4 3 DT SUFFIX PLASTIC PACKAGE CASE 369A (DPAK) Simplified Block Diagram PIN CONNECTIONS Input Gnd 1 2 Output 3 Input 4 8 NC 7 Output 6 5 NC (Top View) Current Limit Output 4 123 Pin 1. Ground 2. Output 3. Input 4. Output (Top View) Ground Thermal Limiting Control Circuit ORDERING INFORMATION Device MC34268D MC34268DT Operating Temperature Range TJ = 0 to +125C Package SOP-8 DPAK 12/96 (c) Motorola, Inc. 1997 1 REV 0 MC34268 MAXIMUM RATINGS Rating Power Supply Input Voltage Power Dissipation and Thermal Characteristics DT Suffix, Plastic Package, Case 369A TA = 25C, Derate Above TA = 25C Thermal Resistance, Junction-to-Case Thermal Resistance, Junction-to-Air D Suffix, Plastic Package, Case 751 TA = 25C, Derate Above TA = 25C Thermal Resistance, Junction-to-Case Thermal Resistance, Junction-to-Air Operating Junction Temperature Range Storage Temperature Symbol Vin Value 15 Unit V PD RJC RJA PD RJC RJA TJ Tstg Internally Limted 5.0 87 Internally Limited 22 140 0 to +150 - 55 to +150 W C/W C/W W C/W C/W C C ELECTRICAL CHARACTERISTICS (Vin = 4.25 V, CO = 10 F, for typical values TJ = 25C, for min/max values TJ = 0C to +125C, unless otherwise noted.) Characteristic Output Voltage (TJ = 25C, IO = 0 mA) Output Voltage, over Line, Load, and Temperature (Vin = 3.9 V to 15 V, IO = 0 mA to 490 mA) Line Regulation (Vin = 4.25 V to 15 V, IO = 0 mA, TJ = 25C) Load Regulation (IO = 0 mA to 800 mA, TJ = 25C) Dropout Voltage (IO = 490 mA) Ripple Rejection (f = 120 Hz) Maximum Output Current (Vin = 5.0 V) Bias Current (Vin = 4.25 V, IO = 0 mA) Minimum Load Current to maintain Regulation (Vin = 15 V) Symbol VO Min 2.81 2.76 -- -- -- 55 800 -- -- Typ 2.85 2.85 -- -- 0.95 -- -- 5.0 to 3.0 -- Max 2.89 2.93 0.3 0.5 1.1 -- -- 8.0 0 Unit V Regline Regload Vin - VO RR I(max) IB IL(min) % % V dB mA mA mA Figure 1. Dropout Voltage versus Output Load Current 1.5 V in-VO , DROPOUT VOLTAGE (V) TJ = 25C 1.3 1.1 0.9 0.7 0.5 I O , OUTPUT CURRENT VO , OUTPUT VOLTAGE DEVIATION Figure 2. Transient Load Regulation Vin = 5.0 V CO = 10 F TA = 25C 0 200 400 600 800 1000 20 ms/DIV IO, OUTPUT LOAD CURRENT (mA) MOTOROLA 2 SCSI TERMINATORS BR1486 0A 0.8 A 5.0 mV/DIV MC34268 Figure 3. Typical SCSI Application Vin 1N5819 10 MC34268 SCSI Regulator Gnd VO CO 10 To SCSI Bus 110 5.0V Figure 3 is a circuit of a typical SCSI terminator application. The MC34268 is designed specifically to provide 2.85 V required to drive a SCSI-2 bus. The output current capability of the regulator is in excess of 800 mA; enough to drive standard SCSI-2, fast SCSI-2, and some wide SCSI-2 applications. The typical dropout voltage is less than 1.0 V, allowing the IC to regulate to input voltages less than 4.0 V. Internal protective features include current and thermal limiting. The MC34268 requires an external 10 F capacitor with an ESR of less than 10 for stability over temperature. With economical electrolytic capacitors, cold temperature operation can pose a stability problem. As temperature decreases, the capacitance also decreases and the ESR increases, which could cause the circuit to oscillate. Tantalum capacitors may be a better choice if small size is a requirement. Also, the capacitance and ESR of a tantalum capacitor is more stable over temperature. JA, THERMAL RESISTANCE JUNCTION-TO-AIR ( C/W) Figure 4. SOP-8 Thermal Resistance versus P.C.B. Copper Length 180 P.C. Board Heatsink Example 160 L 120 80 40 0 0 10 20 30 40 50 L, LENGTH OF COPPER FLAGS (mm) JA, THERMAL RESISTANCE JUNCTION-TO-AIR ( C/W) Figure 5. DPAK Thermal Resistance versus P.C.B. Copper Length 90 P.C. Board Heatsink Example 80 70 60 50 40 0 10 20 30 L, LENGTH OF COPPER (mm) SCSI TERMINATORS BR1486 3 EEEEE EEEEE EEEEE EEEEE EEEEE EEEEE EEEEE 2.0 oz Copper L 9.0 mm L 60 70 L 2.0 oz Copper L 40 MOTOROLA |
Price & Availability of ON1115
 |
|
|
|
|
All Rights Reserved © IC-ON-LINE 2003 - 2022 |
| [Add Bookmark] [Contact Us] [Link exchange] [Privacy policy] |
|
Mirror Sites : [www.datasheet.hk]
[www.maxim4u.com] [www.ic-on-line.cn]
[www.ic-on-line.com] [www.ic-on-line.net]
[www.alldatasheet.com.cn]
[www.gdcy.com]
[www.gdcy.net] |