LM3406_09 Datasheet, PDF (11/26 Pages) National Semiconductor (TI) – 1.5A Constant Current Buck Regulator for Driving High Power LEDs

FIGURE 4. Two Methods of Output Open Circuit Protection
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LOW POWER SHUTDOWN
The LM3406/06HV can be placed into a low power state (I_IN-
SD ^{= 240 µA) by grounding the RON pin with a signal-level}
MOSFET as shown in Figure 5 . Low power MOSFETs like
the 2N7000, 2N3904, or equivalent are recommended de-
vices for putting the LM3406/06HV into low power shutdown.
Logic gates can also be used to shut down the LM3406/06HV
as long as the logic low voltage is below the over temperature
minimum threshold of 0.3V. Noise filter circuitry on the RON
pin can cause a few pulses with longer on-times than normal
after RON is grounded or released. In these cases the OVP/
OCP comparator will ensure that the peak inductor or LED
current does not exceed 300 mV / R_SNS.
FIGURE 5. Low Power Shutdown
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THERMAL SHUTDOWN
Internal thermal shutdown circuitry is provided to protect the
IC in the event that the maximum junction temperature is ex-
ceeded. The threshold for thermal shutdown is 165°C with a
25°C hysteresis (both values typical). During thermal shut-
down the MOSFET and driver are disabled.
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