Note on Use

1. Checking for Intermittent Oscillation

2. PWM/PFM Automatic Switching

3. Ratings

Use the XC9505 series and peripheral components within the limits of their ratings.

The XC9505 series is subject to intermittent oscillation in the proximity of the maximum duty if the step-down ratio is low (e.g.,

from 4.2 V to 3.3 V) or a heavy load is applied where the duty ratio becomes high. Check waveforms at EXT under your

operating conditions. A remedy for this problem is to raise the inductance of coil L or increase the load capacitance CL.

If PWM/PFM automatic switching control is selected and the step-down ratio is high (e.g., from 10.0 V to 1.0 V), the control mode

remains in PFM setting over the whole load range, since the duty ratio under continuous-duty condition is smaller than the PFM

duty ratio of the XC9505series. The output voltage's ripple voltage becomes substantially high under heavy load conditions, with

the XC9505 series appearing to be producing an abnormal oscillation. If this operation becomes a concern, set pins PWM to

High to set the control mode to PWM setting. For use under the above-mentioned condition, measured data of PWM/PFM

automatic switching control shown on the data sheets are available up to IOUT = 100 mA.

XC9505 Series

2ch. Step-Down / Inverting DC/DC Controller ICs

13