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 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.
- 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 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.