When using manual switches to turn on and enable the regulator (fixed 1.8V output device), with the input power supply and Enable already turned on, the regulator puts our 2.7V - 3.7V instead of 1.8V.
I am suspecting the switches are bouncing on the Enable input line and putting the devices into an error state with the wrong output.
Are there cases when the fixed output device could put out different output voltages?
Hi Alula,
Welcome to the forum! May I ask if you are applying any load on the output? Since this part runs in AAM mode for light load operation, it will need a small amount of load to regulate to the 1.8Vout.
Hi Cecilia,
We have an STM32 microcontroller and small flash memory connected to this regulator. It is a small load (10 - 20 mA) initially.
Hi Alula,
You would need a load of about 100-200mA to get the part out of AAM mode. Alternatively, there is a Forced CCM version that is a drop-in replacement that you may ask our team at mpsnow@monolithicpower.com to help procure.
I see. Do you think we would see problems in the AAM mode?
It depends on how you sensitive your output is at no load or a few 10mAs. If it can handle the higher voltage at no load then it is fine. The only other solutions are to apply about 100mA load in this case or to change it to the part with the FCCM mode. There are some parts that have a dedicated pin to change the modes, but unfortunately this does not have that pin.
Hi Cecilia, Is this behavior the same with the 3.3V part also? We may use the MPM3804-33 part on another circuit. Do you know what the minimum current load it requires to maintain regulation?
With any light load (less than 100mA) with the MPM3804, you will see a similar behavior since it is trying to compensate the light load with the voltage. Higher loads than 100mA will be ok.
Thank you. And are there the MPM3804C-33 options available? These options are not shown on datasheet or on website.
Yes, there should be a fixed 3.3Vout available. Please let the sales person you are in contact with that you would like that option and they can help get those for you.