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 7-3 and is 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 Dropout Operation 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 depicted in the third
region of Figure 7-3. 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 decreases.
- The rated input voltage range
governs both the minimum and maximum of VIN – VOUT.
Figure 7-3 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.