Connection of sense resistor in LED driver IC?

[treez]

We have only 3 wires from which we must supply two Buck led drivers. If we use the MIC3205, then can we place the sense resistor at the bottom of the led string instead of the top? –(If so then we will indeed be able to use just 3 wires to supply the two led drivers).

MIC3205 datasheet:
**broken link removed**

 

[KlausST]

Hi,

Placing the resistor in the GND path will not show the same current.

The inductance stores energy when FET is on. During this time both -upper current and gnd current - is the same. But when switch is OFF, then the GND current is zero, while the upper current still flows -supplied by the energy previously stored in the inductance.

Besides this you'd need a very fast OPAMP to generate the bias voltage from gnd resistor to sense input.

Klaus

 

[treez]

ok, but that is not what i mean. I am speaking of putting the sense resistor in series with the leds, but next to the inductor aswell. I am not talking about putting the resistor in the ground path.