ADP2503 Problem



I have a question ADP2503.


◆ Problem
SYNC = Low Power mode is set. * R50 is not mounted, R51 is mounted 2.5V from J2 → Only THD outputs 4V at TH7.
If the switching frequency of L2 is measured with an oscilloscope, it does not stabilize from 2.4 MHz to 2.8 MHz and appears to oscillate.



Problems and checked
· The power supply D 5 V of the step-up regulator "ADP 2503" is not output normally.
I use it in the power down mode.
Current situation, unstable at around 3.9 ~ 4.2V. It also generates noise that oscillates.


· Measurement of oscillation frequency with inductor terminal: It is not stable between 2.4 MHz and 2.8 MHz.
In PWM power-down mode, is it such a thing?


· Parts related: Inductor "NR3015T1R5N" recommended products are mounted.

· Layout: Bottom of inductor is processed without pattern.
In addition, we think that the wiring around the regulator is roughly equivalent to the evaluation board pattern diagram on the data sheet.


Best Regards



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