ADP2389 Output Voltage

Hi Yuya,

#1.  This high output current buck usually provides 8-10mV output voltage differential between No Load and Full Load.  I'm using same series EVAL board to check performance in bench.  The data you got should be good already.

#2.  You may get little improvement by these:
- Move bit to higher Iocp setting
- Ensure Vout ripple is low (< 40mV).  Else add output capacitance
- Observe recommended board layout: taking note of the short power loop at the output & connection of FB pin.
Page 20/21 of datasheet

Thank you.

Hi Yuya,

100mV is not expected.  Line regulation is usually better in performance.  My data is showing typical 4mV at higher loads including full load and 13mV at no load. This is line regulation: 4.5Vin up to 12Vin.

My initial thinking is that at higher Vin up to 10V, your output voltage has started to deviate higher than the target 1V.  Output voltage may well be at 1V during 4.5Vin but started to rise until it goes closer to 1.1V at 10Vin.  Please check if this has been the case.

Beware of the datasheet MIN on-time requirement of 100ns (page 4/23) and therefore of your switching frequency.  This limitation has impact to the duty cycle and eventually the output voltage.  Based on my assessment, the recommended switching frequency to your application is between 800-1,000kHz (lower is better for good margin) so regulation at 10Vin is still ok.  Else, your design should be good only up around 7Vin.

Regards,

Fil

Hi, Fil

Thank you for your answer.

I understood the fluctuation of the voltage due to load fluctuation and the improvement of the load regulation.

Although it is an additional question, even when the input voltage is varied from 4.5 V to 10 V, the output voltage varied by about 100 mV. Is this characteristic of the IC?

Best regards,

Yuya

Hi, Fil

Thank you for a polite answer.
I will check it.

Best Regards,

Yuya