8.3.12 Input Supply Current
The LMR36506-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 VOUT/BIAS pin in the fixed-output voltage variants is the input to the LDO that powers the majority of the control circuits. By connecting the VOUT/BIAS input pin to the output node of the regulator, a small amount of current is drawn from the output. This current is reduced at the input by the ratio of VOUT / VIN.
Equation 3.
where
- IQ_VIN is the total standby (switching) current consumed by the operating (switching) buck converter when unloaded.
- IQ is the current drawn from the VIN terminal. Check IQ_13p5_Fixed or IQ_24p0_Fixed in the Electrical Characteristics for IQ.
- IEN is current drawn by the EN terminal. Include this current if EN is connected to VIN. Check ILKG-EN in the Electrical Characteristics for IEN.
- IBIAS is bias current drawn by the BIAS input. Check IB_13p5 or IB_24p0 in the Electrical Characteristics for IBIAS.
- ηeff is the light-load efficiency of the buck converter with IQ_VIN removed from the input current of the buck converter. ηeff = 0.8 is a conservative value that can be used under normal operating conditions. This can be traced back as the ISUPPLY in the System Characteristics.