S5JGS1581D / S5JGS1581D-25

5-Terminal

Dual Input Dropout Regulators

Elektronische Bauelemente

20-Dec-2011 Rev. A

Page 7 of 8

http://www.SeCoSGmbH.com/

Any changes of specification will not be informed individually.

The bottom of the resistor divider is connected to the bottom of the load. The effect on output regulation can

be seen in trace B of Figure 3. It is important to note that the voltage drops due to Rp are not eliminated; they will

add to the dropout voltage of the regulator regardless. The S5JGS1581D can control the voltage at the load as

long as the input-output voltage is greater than the total of the dropout voltage of the device plus the voltage drop

across Rp.

STABILITY

The circuit design used in the S5JGS1581D series requires the use of an output capacitor as part of the

device frequency compensation. The addition of 150µF aluminum electrolytic or a 22µF solid tantalum on the

output will ensure stability for all operating conditions.

OUTPUT VOLTAGE

The S5JGS1581D (adjustable version) develops a 1.25V reference voltage between the Sense pin and the

Adjust pin (Figure 4). Placing a resistor between these two terminals causes a constant current to flow through R1

and down though R2 to set the output voltage. In general R1 is chosen so that this current is the specified

minimum load current of 5mA. The current out of the Adjust pin is small, typically 50µA and it adds to the current

from R1. For the best regulation the top of the resistor divider should be connected directly to the Sense pin.

THERMAL CONSIDERATIONS

The S5JGS1581D series have internal power and thermal limiting circuitry designed to protect the device

under overload conditions. However, maximum junction temperature ratings should not be exceeded under

continuous normal load conditions. Careful consideration must be given to all sources of thermal resistance from

junction ambient, including junction to case, case to-heat sink interface and heat sink resistance itself. Junction

temperature of the control section can run up to 125ºC. Junction temperature of the Power section can run up to

150ºC.