Datasheet LT1118, LT1118-2.5, LT1118-2.85, LT1118-5 (Analog Devices) - 5
| Fabricante | Analog Devices |
| Descripción | Low IQ, Low Dropout, 800mA, Source and Sink Regulators Adjustable and Fixed 2.5V, 2.85V, 5V Output |
| Páginas / Página | 8 / 5 — PIN FUNCTIONS. IN:. OUT:. GND:. FB:. EN:. LT1118 Adjustable. OPERATION. … |
| Formato / tamaño de archivo | PDF / 253 Kb |
| Idioma del documento | Inglés |
PIN FUNCTIONS. IN:. OUT:. GND:. FB:. EN:. LT1118 Adjustable. OPERATION. Output Capacitor. Thermal Considerations
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- LT1118CS8#PBF LT1118CS8#PBF LT1118CS8#TRPBF LT1118CS8#TRPBF LT1118CS8-2.5#PBF LT1118CS8-2.5#PBF LT1118CS8-2.5#TRPBF LT1118CS8-2.5#TRPBF LT1118CS8-2.85#PBF LT1118CS8-2.85#PBF LT1118CS8-2.85#TRPBF LT1118CS8-2.85#TRPBF LT1118CS8-5#PBF LT1118CS8-5#PBF LT1118CS8-5#TRPBF LT1118CS8-5#TRPBF LT1118CST-2.5#PBF LT1118CST-2.5#PBF LT1118CST-2.5#TRPBF LT1118CST-2.5#TRPBF LT1118CST-2.85#PBF LT1118CST-2.85#PBF LT1118CST-2.85#TRPBF LT1118CST-2.85#TRPBF LT1118CST-5#PBF LT1118CST-5#PBF LT1118CST-5#TRPBF LT1118CST-5#TRPBF
Versión de texto del documento
LT1118/LT1118-2.5 LT1118-2.85/LT1118-5
PIN FUNCTIONS IN:
Input Supply Pin. This pin should be decoupled with
OUT:
Regulated Output Voltage. Output can source or sink a 1μF or larger low ESR capacitor. The two IN pins on the current. Current limit for sourcing and sinking current is SO-8 package must be directly connected on the printed provided to protect the device from fault conditons. The circuit board to prevent voltage drops between the two output must have a low ESR output fi lter capacitor. COUT inputs. When used as a SCSI active termination, IN con- ≥ 0.22μF to guarantee stability. A 0.1μF ceramic capacitor nects to term power. When used as a supply splitter, IN is may be needed in parallel with COUT if the ESR of the main also the positive supply output. COUT is too high.
GND:
Ground Pin. The multiple GND pins on the SO-8
FB:
Feedback Pin. The feedback pin is used to program package are internally connected, but lowest load regulation the output voltage of the adjustable S8 part. The output errors will result if these pins are tightly connected on the voltage range that can be achieved is 2.1V to 6.5V. The printed circuit board. This will also aid heat dissipation at output voltage is determined by the selection of feedback high power levels. resistors defi ned by the following formula:
EN:
TTL/CMOS Logic Input. A high level allows normal VOUT = VFB (1 + R1/R2) + IFBR1 operation. A low level reduces supply current to zero. This pin is internally connected to VIN on 3-lead ST packaged
LT1118 Adjustable
devices. R V 1 IN IN OUT V 1 + ( ) OUT = VFB + I R FB R1 2 1μF 1μF LT1118 R1 EN GND FB R2 1118 TA06
OPERATION Output Capacitor
Worst case transient response of the LT1118 regulators occurs at zero output current. In order to obtain the fastest The LT1118 family of voltage regulators require an output transient settling performance, the regulator output may capacitor for stability. The regulators are stable with out- be preloaded with a small current. The preload current put capacitors larger than 0.2μF. Load transient response reduces the regulator output impedance, reducing output is very sensitive to output capacitor value and dielectric voltage settling time. choice. Low ESR ceramic capacitors are the best choice for fast settling to load transients. Output capacitors
Thermal Considerations
between 0.2μF and 1μF give good performance in most applications. Larger tantalum output capacitors may be The LT1118 regulators are packaged in plastic SOT-223 and used to reduce load transient amplitudes. Larger capaci- fused lead S8 packages. These small footprint packages tors should be paralleled with a 0.1μF ceramic capacitor are unable to convectively dissipate the heat generated to maintain quick settling time performance and to insure when the regulator is operating at high current levels. In stability of the regulator control loop. Capacitors larger order to control die operating temperatures, the PC board than 10μF may be safely used with the regulators, but layout should allow for maximum possible copper area at little transient settling performance improvement results the ground pins of the LT1118. The ground pins and the from their use. tab on the SOT-223 package are electrically and thermally 1118fd 5
PIN FUNCTIONS IN:
Input Supply Pin. This pin should be decoupled with
OUT:
Regulated Output Voltage. Output can source or sink a 1μF or larger low ESR capacitor. The two IN pins on the current. Current limit for sourcing and sinking current is SO-8 package must be directly connected on the printed provided to protect the device from fault conditons. The circuit board to prevent voltage drops between the two output must have a low ESR output fi lter capacitor. COUT inputs. When used as a SCSI active termination, IN con- ≥ 0.22μF to guarantee stability. A 0.1μF ceramic capacitor nects to term power. When used as a supply splitter, IN is may be needed in parallel with COUT if the ESR of the main also the positive supply output. COUT is too high.
GND:
Ground Pin. The multiple GND pins on the SO-8
FB:
Feedback Pin. The feedback pin is used to program package are internally connected, but lowest load regulation the output voltage of the adjustable S8 part. The output errors will result if these pins are tightly connected on the voltage range that can be achieved is 2.1V to 6.5V. The printed circuit board. This will also aid heat dissipation at output voltage is determined by the selection of feedback high power levels. resistors defi ned by the following formula:
EN:
TTL/CMOS Logic Input. A high level allows normal VOUT = VFB (1 + R1/R2) + IFBR1 operation. A low level reduces supply current to zero. This pin is internally connected to VIN on 3-lead ST packaged
LT1118 Adjustable
devices. R V 1 IN IN OUT V 1 + ( ) OUT = VFB + I R FB R1 2 1μF 1μF LT1118 R1 EN GND FB R2 1118 TA06
OPERATION Output Capacitor
Worst case transient response of the LT1118 regulators occurs at zero output current. In order to obtain the fastest The LT1118 family of voltage regulators require an output transient settling performance, the regulator output may capacitor for stability. The regulators are stable with out- be preloaded with a small current. The preload current put capacitors larger than 0.2μF. Load transient response reduces the regulator output impedance, reducing output is very sensitive to output capacitor value and dielectric voltage settling time. choice. Low ESR ceramic capacitors are the best choice for fast settling to load transients. Output capacitors
Thermal Considerations
between 0.2μF and 1μF give good performance in most applications. Larger tantalum output capacitors may be The LT1118 regulators are packaged in plastic SOT-223 and used to reduce load transient amplitudes. Larger capaci- fused lead S8 packages. These small footprint packages tors should be paralleled with a 0.1μF ceramic capacitor are unable to convectively dissipate the heat generated to maintain quick settling time performance and to insure when the regulator is operating at high current levels. In stability of the regulator control loop. Capacitors larger order to control die operating temperatures, the PC board than 10μF may be safely used with the regulators, but layout should allow for maximum possible copper area at little transient settling performance improvement results the ground pins of the LT1118. The ground pins and the from their use. tab on the SOT-223 package are electrically and thermally 1118fd 5