SW

LM3402

GND

CS

8V

~ 0.67

5

Module

Connector

Module

Connector

1 k

5

SW

LM3402

GND

CS

8V

~ 0.67

5

Module

Connector

Module

Connector

LM3402, LM3402HV

www.ti.com

SNVS450E – SEPTEMBER 2006 – REVISED MAY 2013

Figure 24. CS Pin, Transient Path

Figure 25. CS Pin, Transient Path with Protection

Adding a resistor in series with the CS pin causes the observed 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 1k

Ω 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 threshold. These are both very minor changes and are well understood. The shift

in current can either be neglected or taken into consideration by changing the current sense resistance slightly.

Copyright © 2006–2013, Texas Instruments Incorporated

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