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 shown in Figure 8-3 and can be separated into the following regions:
- Dropout voltage limits the minimum differential
voltage between the input and the output (VIN – VOUT)
at a given output current level; see the Section 7.4.2 section for more details.
- The rated output current 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.
- Figure 8-3
provides the shape of the slope. 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 8-3 Continuous Operation Diagram With Description of Regions