LP3871 Datasheet, PDF (11/14 Pages) National Semiconductor (TI) – 0.8A Fast Ultra Low Dropout Linear Regulators

Application Hints (Continued)
FIGURE 1. Error Flag Operation
20063107
SENSE PIN
In applications where the regulator output is not very close to
the load, LP3874 can provide better remote load regulation
using the SENSE pin. Figure 2 depicts the advantage of the
SENSE option. LP3871 regulates the voltage at the output
pin. Hence, the voltage at the remote load will be the regu-
lator output voltage minus the drop across the trace resis-
tance. For example, in the case of a 3.3V output, if the trace
resistance is 100mΩ, the voltage at the remote load will be
3.22V with 0.8A of load current, I_LOAD. The LP3874 regulates
the voltage at the sense pin. Connecting the sense pin to the
remote load will provide regulation at the remote load, as
shown in Figure 2. If the sense option pin is not required, the
sense pin must be connected to the V_OUT pin.
FIGURE 2. Improving remote load regulation using LP3874
20063108
SHUTDOWN OPERATION
A CMOS Logic level signal at the shutdown ( SD) pin will
turn-off the regulator. Pin SD must be actively terminated
through a 10kΩ pull-up resistor for a proper operation. If this
pin is driven from a source that actively pulls high and low
(such as a CMOS rail to rail comparator), the pull-up resistor
is not required. This pin must be tied to Vin if not used.
11
www.national.com