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 8-3 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 7.4.3 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 4. 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 shows the recommended area of operation for this device on a JEDEC-standard high-K board with a RθJA as given in the Thermal Information table.
Figure 8-3 Region Description of Continuous Operation Regime