S5JGS1581D / S5JGS1581D-25

5-Terminal

Dual Input Dropout Regulators

Elektronische Bauelemente

20-Dec-2011 Rev. A

Page 6 of 8

http://www.SeCoSGmbH.com/

Any changes of specification will not be informed individually.

Application Information

The S5JGS1581D series of adjustable and fixed regulators are designed to power the new generation of

microprocessors. The S5JGS1581D is designed to make use of multiple power supplies, present in most systems,

to reduce the dropout voltage. One of the advantages of the two supply approach is maximizing the efficiency.

The second supply is at least 1V greater than output voltage and is providing the power for the control circuitry

and supplies the drive current to the NPN output transistor. This allows the NPN output transistor to be driven into

saturation. For the control voltage the current requirement is small equal to about 1% of the output current. This

drive current becomes part of the output current. The maximum voltage on the Control pin is 12V. The maximum

voltage at the Power pin is 7V. By tying the control and power inputs together the S5JGS1581D can also be

operated as a single supply device. In single supply operation the dropout will be determined by the minimum

control voltage.

Both fixed and adjustable versions have remote sense pins, permitting very accurate regulation of output

voltage. As a result, over an output current range of 100mA ~ 5A, the typical load regulation are less than 1mV. For

the fixed voltages the adjust pin is brought out allowing the user to improve transient response by bypassing the

internal resistor divider. Optimum transient response is provided using a capacitor in the range of 0.1µF ~ 1µF for

bypassing the Adjust pin.

In addition to the enhancements mentioned, the reference accuracy has been improved by a factor of two with

a guaranteed initial tolerance of ±1% at 25ºC and 1.6% accuracy over the full temperature and load current range.

Typical applications for the S5JGS1581D include 3.3V to 2.5V conversion with a 5V control supply, 5V to 4.2V

conversion with a 12V control supply. The device is fully protected against over current and over temperature

conditions.

GROUNDING AND OUTPUT SENSEING

The S5JGS1581 allows true Kelvin sensing for both the high and low side of the load. As a result the voltage

regulation at the load can be easily optimized. Voltage drops due to parasitic resistances between the regulator

and the load can be placed inside the regulation loop. The advantages of the remote sensing are illustrated in

Figures 1 through 3.

Figure 1 shows the device connected as a conventional 3 terminal regulator with the sense lead connected

directly to the output of the device. Rp is the parasitic resistance of the connections between the device and the

load. Trace A of Figure 3 illustrates the effect of Rp.

Figure 2 shows the device connected to take advantage of the remote sense feature. The Sense pin and the

top of the resistor divider are connected to the top of the load.