The LMR436x0-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/FB 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/FB 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 as described
in Equation 2.
- IQVIN is the total
standby (switching) current consumed by the operating (switching) buck
converter when unloaded.
- IQ is the current
drawn from the VIN terminal.
- IEN is current
drawn by the EN terminal. Include this current if EN is connected to VIN.
Check ILKG-EN in Section 7.5 for IEN.
- IBIAS is bias
current drawn by the BIAS LDO.
- ηeff is the
light-load efficiency of the buck converter with IQVIN removed
from the input current of the buck converter. ηeff = 0.8 is a
conservative value that can be used under normal operating conditions.