Rev. 10/2/00

AS1582

BLOCK DIAGRAM

APPLICATIONS NOTES

The AS1582 is designed as a high performance and low cost

solution for application requiring a lower dropout than

traditional NPN regulators.

≥

2.5V power for the load to come from a 3.3V system supply.

As added benefit this will reduce the heat dissipation, and

lower heatsink and cooling fan cost. A typical application

power supply to provide a nominal 2.5V output. Using the

sense pin allows to Kelvin measure the output, reducing

resistive-associated errors.

The AS1582 can power the 2.5V core voltage for

microprocessors such as Pentium

, P55C, AMD5k86

and K6

 and the IBM PowerPC 603EV and 604EV

processors.

*The reduction of heat dissipation is a result of the increase of the regulator

Adjustable Regulator Design

1.25V reference voltage is being developed between the

SENSE pin and the ADJ pin of the AS1582. Adding two

external resistors (see fig 1.) will allow setting the output

flowing from the ADJ pin is typically 50

µA. This ADJ pin

contributes to the final VOUT but is usually neglected.

Connecting the sense pin to the top of the resistor divider will

improve load regulation.

Lowering Noise

Using the SENSE pin to Kelvin the load will increase accuracy

of the output voltage during load regulation. For the fixed

voltage devices, adding a capacitor at the GND pin will

improve transient response. This capacitor is chosen in the

range of 1

µF to 0.1µF and will depend on the amount of

output capacitance in the system.

PIN DESCRIPTION

device).

2. ADJ = Negative side of the reference voltage for the device. Adding a small bypass capacitor

from the ADJ pin to ground will improve the transient response.

voltage for the device to regulate.

greater than the output voltage for the device to regulate.

(4) V

CTRL

V

S.O.A

V

LIMIT

SENSE

CURRENT

LIMIT

AMPLIFIER

THERMAL OVERLOAD

VOLTAGE

REGULATION

AMPLIFIER

V

REF

SENSE (1)

ADJ (2)