LM3402MR/NOPB National Semiconductor, LM3402MR/NOPB Datasheet - Page 17
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LM3402MR/NOPB
Manufacturer Part Number
LM3402MR/NOPB
Description
IC LED DRVR HP CONST CURR 8-PSOP
Manufacturer
National Semiconductor
Series
PowerWise®r
Type
High Power, Constant Currentr
Datasheet
1.LM3402MRNOPB.pdf
(28 pages)
Specifications of LM3402MR/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 ~ 42 V
Mounting Type
Surface Mount
Package / Case
8-PSOP
Operating Temperature
-40°C ~ 125°C
Current - Output / Channel
500mA
Internal Switch(s)
Yes
Efficiency
96%
For Use With
551600000-001A/NOPB - BOARD WEBENCH SO8/SOP LM3404/2551600003-001A - BOARD WEBENCH MSOP LM3402LM3402EVAL - BOARD EVALUATION FOR LM3402
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Voltage - Output
-
Other names
LM3402MR
Adding a resistor in series with the CS pin causes the ob-
served output LED current to shift very slightly. The reason
for this is twofold: (1) the CS pin has about 20pF of inherent
capacitance inside it which causes a slight delay (20ns for a
1kΩ series resistor), and (2) the comparator that is watching
the voltage at the CS pin uses a pnp bipolar transistor at its
input. The base current of this pnp transistor is approximately
100nA which will cause a 0.1mV change in the 200mV thresh-
old. These are both very minor changes and are well under-
stood. The shift in current can either be neglected or taken
into consideration by changing the current sense resistance
slightly.
CS PIN PROTECTION WITH OVP
When designing output overvoltage protection into the switch-
ing converter circuit using a zener diode, transient protection
FIGURE 7. CS Pin, Transient Path with Protection
17
on the CS pin requires additional consideration. As shown in
Figure
(with the series resistor) for output overvoltage protection will
now again allow the transient energy to be passed through
the CS pin’s ESD structure thereby damaging it.
Adding an additional series resistor to the CS pin as shown
in
pass through the sense resistor thereby protecting the
LM340X device.
Figure 9
8, adding a zener diode from the output to the CS pin
will result in the majority of the transient energy to
20192159
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