The LM61430-Q1 is designed to have very low input supply current when regulating light loads. This is achieved 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 pin to the output of the regulator, a small amount of current drawn from the output. This current is reduced at the input by the ratio of V_OUT / V_IN.

Equation 4.

where

• I_{Q_VIN(SW)} = Current consumed by the operating (switching) buck converter while unloaded
• I_{Q_VIN} = Nonswitching input current. See I_{Q_VIN} in the Electrical Characteristics.
• I_EN = Current drawn by the EN terminal. Include this current if EN is connected to VIN. See I_EN in the Electrical Characteristics. Note that this current drops to a very low value if connected to a voltage less than 5 V.
• I_div = Current drawn by the feedback voltage divider used to set output voltage
• η_eff Light-load efficiency of the buck converter with I_{Q_VIN} removed from the input current of the buck converter. η_eff = 0.8 is a conservative value that can be used under normal operating conditions.