◈ Typical application circuit
D io de
V re f
3 C rref
V rin 7
The voltage control is given by the choice of the resistor bridge R6/R7 (and the trimmer R8)
Vref = R6/(R6+R7)xVout
where Vref = 1.24V
The current control is given by the choice of the voltage drop through the sense resistor R5 (to be linked to the
nominal current of the application) and by the value of the sense resistor itself.
For medium currents (< 1A), a good value for the voltage drop through R5 can be Vsense = 200mV
(dissipation < 200mW). The resistor bridge R2/R3 should be chosen following
Vsense = R3/(R2+R3)xVref
The total value of the resistor bridge should be in the range of the kin order to ensure a proper charge for the
voltage reference(in the range of themA).
To set the current limit, the senseresistorR5should be chosen following
Ilim = Vsense/R5
The internal current generator (Isce) can be used to offset the current limitation with a lower value.
This current generator is activated by connecting pin 2 to ground. It is inhibited if pin 2 is connected
to the positive rail via the pull up resistor R1. The current offset is given by the choice of the
resistor R4. If Ilim1 is the current limit calculated in the previous paragraph, and Ilim2 is the current limit that is to
be set when pin 2 is connected to ground, R4 should be chosen following
R4 = (Vsense - Ilim2xR5)/Isce
Dec, 2011 REV. 00