The LM53625/35-Q1 is designed to have very low input supply current when regulating light loads. One way this is achieved is by powering much of the internal circuitry from the output. The BIAS pin is the input to the LDO that powers the majority of the control circuits. By connecting the BIAS input to the output of the regulator, this current acts as a small load on the output. This current is reduced by the ratio of VOUT/VIN, just like any other load. Another advantage of the LM53625/35-Q1 is that the feedback divider is integrated into the device. This allows the use of much larger resistors than can be used externally; >> 100 kΩ. This results in much lower divider current than is possible with external resistors.
Equation 2 can be used as a guide to indicate how the various terms affect the input supply current in AUTO mode in unloaded conditions. TheApplication Curves show measured values for the input supply current for both the 3.3-V and the 5-V output voltage versions.