VIN

LM3402

GND

80V

Module

Connector

Module

Connector

TVS

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 1k

Ω 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

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.

22

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