LM3406MH National Semiconductor, LM3406MH Datasheet - Page 14

• Manufacturer Part Number: LM3406MH
• Description: LM3406/06HV 1.5A Constant Current Buck Regulator for Driving High Power LEDs; Package: TSSOP EXP PAD; No of Pins: 14; Qty per Container: 94; Container: Rail
• Manufacturer: National Semiconductor

www.national.com
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
FIGURE 8. CS Pin, Transient Path with Protection
FIGURE 7. CS Pin, Transient Path
14
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.
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