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XC9502

Series

■NOTES ON USE

2. PWM/PFM Automatic Switching

If PWM/PFM automatic switching control is selected and the step-up ratio is low (e.g., from 4.5V to 5.0V) or the

step-down ratio is high (e.g., from 10.0V to 1.0 V), the control mode remains in PFM setting in the whole load range,

since the duty ratio under continuous-duty condition is smaller than the PFM duty ratio of the XC9502 series. The

output voltage's ripple voltage becomes substantially high under heavy load conditions, with the XC9502 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

1.Checking for Intermittent Oscillation

The XC9502 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

3. Ratings

Use the XC9502 series and external components within the limits of their ratings.