The operational area of an LDO is limited by
the dropout voltage, output current, junction temperature, and input voltage. The
recommended area for continuous operation for a linear regulator is given in Figure 8-6 and can be separated into the following parts:
- Dropout voltage limits the minimum
differential voltage between the input and the output (VIN – VOUT)
at a given output current level. See the Section 8.1.6 section for more details.
- The rated output currents limits the
maximum recommended output current level. Exceeding this rating causes the device to
fall out of specification.
- The rated junction temperature limits
the maximum junction temperature of the device. Exceeding this rating causes the device
to fall out of specification and reduces long-term reliability.
- The shape of the slope is given by
Equation 6. The slope is nonlinear because the maximum rated junction
temperature of the LDO is controlled by the power dissipation across the LDO; thus
when VIN – VOUT increases the output current must
decrease.
- The rated input voltage range governs
both the minimum and maximum of VIN – VOUT.
Figure 8-6 shows the recommended area of operation for this device on a JEDEC-standard high-K board
with a RθJA as given in the Recommended Operating Conditions table.