IFX30081SJV
Application Information
Data Sheet 20 Rev. 1.0, 2015-02-04
6.2.2 Output Pin
An output capacitor is mandatory for the stability of linear voltage regulators.
The requirement to the output capacitor is given in “Functional Range” on Page 7. The graph “Output
Capacitor Series Resistor ESR(COUT) versus Output Current IOUT” on Page 12 shows the stable operation
range of the device.
IFX30081SJV is designed to be stable with extremely low ESR capacitors.
The output capacitor should be placed as close as possible to the regulator’s output and GND pins and on the
same side of the PCB as the regulator itself.
In case of rapid transients of input voltage or load current, the capacitance should be dimensioned in accordance
and verified in the real application that the output stability requirements are fulfilled.
6.3 Output Voltage Adjust
The output voltage of IFX30081SJV can be adjusted between 1.2 V and VIN -Vdr by an external resistor divider,
connected to the adjust pin ADJ, as shown in Figure 4.
The ADJ pin is connected internally to an error amplifier comparing the voltage at this pin with the internal
reference voltage of typically 1.2 V.
The output voltage can be easily calculated, neglecting the current flowing into the ADJ pin:
(6.1)
with
•Vref: internal reference voltage, typically 1.2V
•R1: resistor between regulator output OUT and adjust pin ADJ
•R2: resistor between adjust pin ADJ and GND
The bigger the resistors R1 and R2, the less the current flowing through the resistor divider. However, using very
big resistors makes the current flowing into the ADJ pin non-negligible. In oder to neglect the current flowing into
the ADJ pin, the values of R1 and R2 should be selected fulfilling the criteria R2 250 k.
To set the output voltage to 1.2 V, the adjust pin ADJ should be directly connected to the output pin OUT.
Take into consideration that an additional error to the output voltage tolerance may be introduced by the accuracy
of the resistors R1 and R2.
6.4 Thermal Considerations
Knowing the input voltage, the output voltage and the load profile of the application, the total power dissipation
can be calculated:
(6.2)
with
•PD: continuous power dissipation
•VIN: input voltage
•VOUT: output voltage
•IOUT: output current
•Iq: quiescent current