Datasheet

VIN
LM3402
GND
80V
V
IN
Module
Connector
Module
Connector
TVS
C
IN
Board Trace
Inductance
TVS or
smaller
zener diode
LM3402, LM3402HV
SNVS450E –SEPTEMBER 2006–REVISED MAY 2013 www.ti.com
Figure 29. VIN Pin with Additional Input Protection
GENERAL COMMENTS REGARDING OTHER PINS
Any pin that goes “off-board” through a connector should have series resistance of at least 1kΩ to 10kΩ in series
with it to protect it from ESD or other transients. These series resistors limit the peak current that can flow (or
cause a voltage drop) during a transient event, thus protecting the pin and the device. Pins that are not used
should not be left floating. They should instead be tied to GND or to an appropriate voltage through resistance.
Design Example 1: LM3402
The first example circuit will guide the user through component selection for an architectural accent lighting
application. A regulated DC voltage input of 24V ±10% will power a single 1W white LED at a forward current of
350 mA ±5%. The typical forward voltage of a 1W InGaN LED is 3.5V, hence the estimated average output
voltage will be 3.7V. The objective of this application is to place the complete current regulator and LED in the
compact space formerly occupied by an MR16 halogen light bulb. (The LED will be on a separate metal-core
PCB.) Switching frequency will be as fast as the 300 ns t
ON
limit allows, with the emphasis on space savings over
efficiency. Efficiency cannot be ignored, however, as the confined space with little air-flow requires a maximum
temperature rise of 40°C in each circuit component. A complete bill of materials can be found in Table 1 at the
end of this datasheet.
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