Datasheet LT1585-1.5, LT1585A-1.5 (Analog Devices) - 4

LT1585-1.5/LT1585A-1.5
W W SI PLIFIED SCHE ATIC
VIN + – THERMAL LIMIT VOUT GND 1585-1.5 SS
U U W U APPLICATIONS INFORMATION General
The LT1585-1.5/LT1585A-1.5 3-terminal regulators are ments of these applications and save total cost by needing easy to use and have all the protection features expected less output capacitance in order to maintain regulation. in high performance linear regulators. The devices are short-circuit protected, safe-area protected and provide
Stability
thermal shutdown to turn off the regulators if the junction The circuit design in the LT1585-1.5/LT1585A-1.5 re- temperature exceeds about 150°C. quires the use of an output capacitor as part of the The ICs are pin compatible with the LT1083/LT1084/LT1085 frequency compensation. For all operating conditions, the family of linear regulators but offer lower dropout voltage addition of a 22µF solid tantalum or a 100µF aluminum and faster transient response. The trade-off for this im- electrolytic on the output ensures stability. Normally, the proved performance is a 7V maximum supply voltage. LT1585-1.5/LT1585A-1.5 can use smaller value capaci- Similar to the LT1083/LT1084/LT1085 family, the LT1585- tors. Many different types of capacitors are available and 1.5/LT1585A-1.5 regulators require an output capacitor for have widely varying characteristics. These capacitors differ stability. However, the improved frequency compensation in capacitor tolerance (sometimes ranging up to ±100%), permits the use of capacitors with much lower ESR while still equivalent series resistance, equivalent series inductance maintaining stability. This is critical in addressing the needs and capacitance temperature coefficient. The LT1585-1.5/ of modern low voltage, high speed microprocessors. LT1585A-1.5 frequency compensation optimizes frequency response with low ESR capacitors. In general, use capaci- Current generation microprocessors and their associated tors with an ESR of less than 1Ω. circuitry cycle load current from almost zero to several amps in tens of nanoseconds. Output voltage tolerances Normally, capacitor values on the order of several hundred are tighter and include transient response as part of the microfarads are used on the output of the regulators to specification. The LT1585-1.5/LT1585A-1.5 are specifi- ensure good transient response with heavy load current cally designed to meet the fast current load step require- changes. Output capacitance can increase without limit and larger values of output capacitance further improve the 4