LM3404HVMR/NOPB National Semiconductor, LM3404HVMR/NOPB Datasheet - Page 12

• Manufacturer Part Number: LM3404HVMR/NOPB
• Description: IC LED DRVR HP CONST CURR 8-PSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: High Power, Constant Currentr

Specifications of LM3404HVMR/NOPB

• Constant Current: Yes
• Topology: PWM, Step-Down (Buck)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Automotive
• Type - Secondary: High Brightness LED (HBLED), White LED
• Frequency: 1MHz
• Voltage - Supply: 6 V ~ 75 V
• Mounting Type: Surface Mount
• Package / Case: 8-PSOP
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 1A
• Internal Switch(s): Yes
• Efficiency: 96%
• Current, Input Bias: 0.1 μA
• Current, Output: 1.2 A
• Current, Supply: 625 μA
• Package Type: PSOP
• Regulator Type: Buck (Step-Down), Switching
• Temperature, Operating, Range: -40 to +125 °C
• Time, Fall: 20 ns
• Time, Rise: 20 ns
• Voltage, Input: 6 to 75 V
• Voltage, Output: 7 V
• For Use With: 551600000-001A/NOPB - BOARD WEBENCH SO8/SOP LM3404/2LM3404HVEVAL - BOARD EVALUATION LM3404HV
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device
• Other names: LM3404HVMR

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V
for the output current. Output current overshoot is limited to
300 mV / R
The OVP/OCP comparator can also be used to prevent the
output voltage from rising to V
open-circuit. This is the most common failure mode for LEDs,
due to breaking of the bond wires. In a current regulator an
output open circuit causes V
maximum duty cycle.
diode, Z1, and zener limiting resistor, R
age to the reverse breakdown voltage of Z1 plus 200 mV. The
zener diode reverse breakdown voltage, V
than the maximum combined V
maximum recommended value for R
LOW POWER SHUTDOWN
The LM3404/04HV can be placed into a low power state (I
SD
MOSFET as shown in
2N7000, 2N3904, or equivalent are recommended devices
for putting the LM3404/04HV into low power shutdown. Logic
gates can also be used to shut down the LM3404/04HV as
SNS
= 90 µA) by grounding the RON pin with a signal-level
exceeds 300 mV. This threshold provides a hard limit
SNS
by this comparator during transients.
Figure 2
Figure
3. Low power MOSFETs like the
SNS
O(MAX)
shows a method using a zener
F
of all LEDs in the array. The
to fall to zero, commanding
in the event of an output
Z
is 1 kΩ.
Z
, to limit output volt-
FIGURE 2. Output Open Circuit Protection
Z
, must be greater
FIGURE 3. Low Power Shutdown
IN-
12
As discussed in the Maximum Output Voltage section, there
is a limit to how high V
that is always less than V
output stage of the LM3404/04HV is capable of withstanding
V
the inductor will oscillate and can go above V
A small (typically 10 nF) capacitor across the LED array
dampens this oscillation. For circuits that use an output ca-
pacitor, the system can still withstand V
long as C
blocked in output open-circuit and the risk of thermal stress is
minimal, hence the user may opt to allow the output voltage
to rise in the case of an open-circuit LED failure.
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
O(MAX)
indefinitely, however the voltage at the output end of
O
is rated to handle V
O
can rise during an output open-circuit
IN
. If no output capacitor is used, the
20205412
IN
. The high current paths are
20205413
SNS
.
O(MAX)
IN
indefinitely as
or below 0V.