Notes on Use

1. Checking for Intermittent Oscillation

2. PWM/PFM Automatic Switching

3. Ratings

Use the XC9503 series and peripheral components within the limits of their ratings.

XC9503 Series

2ch. Step-down DC/DC Controller ICs

The XC9503 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 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 XC9503 series. The output voltage's ripple voltage becomes substantially high under heavy load conditions, with

the XC9503 series appearing to be producing an abnormal oscillation. If this operation becomes a concern, set pins PWM1 and

PWM2 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.

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