LM3411 Datasheet, PDF (11/13 Pages) National Semiconductor (TI) – Precision Secondary Regulator/Driver

Applications Information (Continued)
DS011987-22
FIGURE 10. Precision Negative Voltage Regulator
DS011987-25
FIGURE 13. ±50 mV External Trim
The LM3411 is guaranteed to drive a 15 mA load, but if more
current is needed, a NPN boost transistor can be added. The
circuit shown in Figure 14 is a shunt regulator capable of pro-
viding excellent regulation over a very wide range of current.
DS011987-23
FIGURE 11. Precision Negative Voltage
Regulator with Accurate Current Limit
A simple 5V supply monitor circuit is shown in Figure 12. Us-
ing the LM3411’s voltage reference, op-amp (as a compara-
tor) and output driver, this circuit provides a LED indication of
the presence of the 5V supply.
DS011987-26
FIGURE 14. 250 mA Shunt Regulator
Perhaps one of the simplest applications for the LM3411 is
the voltage detector circuit shown in Figure 15 . The OUT pin
is low when the input voltage is less than V_REG. When the
V(IN) pin rises above V_REG, the OUT pin is pulled high by the
internal NPN output resistor.
DS011987-24
FIGURE 12. 4.7V Power ON Detector with Hysteresis
The LM3411 initial room temperature tolerance is ±1% and
±0.5% for the “A” grade part. If a tighter tolerance is needed,
a trim scheme is shown in Figure 13 that provides approxi-
mately ±1% adjustment range of the regulation voltage
(V_REG).
DS011987-27
FIGURE 15. Voltage Detector
Also an overvoltage detector, the crowbar circuit shown in
Figure 16 is normally located at the output of a power supply
to protect the load from an overvoltage condition should the
power supply fail with an input/output short.
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