Overcurrent Detection Value Setting
The overcurrent detection value VTH for this IC series is 0.2 V (Typ) and the bias current is 200 µA (Typ)
The power MOS FET peak current value before the current limiter goes into operation is derived from the
VTCL − (RF + RCS) ⋅ IBCL
Here VTH = VIN – VCL = 0.2 V, VCL is a voltage referd on GND.
Note that CF and RCS form a low-pass filter, determined by their time constants, that prevents malfunctions
from current spikes when the power MOS FET is turned on or off.
CF 1800 PF
This circuit is an example
for step-down output use.
Figure 8.1 Example for Step-Down Use
The sample values given in this figure are calculated from the following equation.
0.2 V − (240 Ω + 0.05 Ω) × 200 µA
= 3.04 [A]
The filter cutoff frequency is calculated as follows.
2π CF RF
6.28 × 1800 pF × 240 Ω
= 370 [kHz]
Rev.2.0, Sep.18.2003, page 20 of 33