MP2313 - AAM voltage

DC-DC Power Converters
#1

Good Morning,

I’d like to ask some additional information concerning your part number MP2313; what is the relation between the AAM voltage and the light load current? Figure 7. of the datasheet provides some optimized values of AAM voltage, however it is not clear at which value of load current the transition from AAM to PWM and viceversa occurs. For my application, the input voltage will vary from 5.2 to 8.2V, the output voltage is 3.3V, the inductor value is 4.7uH; I want the IC to switch to AAM when the load current falls below 100mA; what is the required value for AAM voltage?

Thank you so much. Kind regards.

#2

Hi a.rigoli,

In the efficiency plots in page you can see that there is an efficiency dip between 100-300mA in each line plot. This is where the device switches over from AAM to PWM. You can see that this switchover happens at a different point in each input voltage, so switching over from 8.2V could potentially happen later than at 5.2V.

With that said, Figure 6 shows how to calculate the AAM voltage. This is useful because the device is in AAM when VCOMP < VAAM and VFB < VREF. The VCOMP is hard to calculate for, my suggestion is to use trial and error in the worst case scenario (8.2V down to 3.3V) to get the AAM setting.

Thanks,
Brendan

#3

Good Morning,

thanks for the reply.

I understand that with the same AAM voltage, the switch from AAM to PWM will occur at different current load level depending on the input voltage.
Figure 7. shows optimized values only for 12-19V input voltage range.
Given that the nominal voltage of my application will be 7.2V, output voltage of 3.3V, and inductor value of 4.7uH, could you suggest an optimal AAM voltage value for the transition to occur at ca.100mA?ù

Thank you. Kind regards.

#4

Unfortunately we can’t directly measure the COMP voltage, meaning we will need to rely on trial and error. I suggest starting at an AAM value around 0.3 - 0.35V and then testing to find the switch over current and adjusting the AAM voltage from there. I would test the stability to make sure you keep a stable system as well.

Thanks,
Brendan

#5

Ok, I understand.

Thank you for the suggestions!

Kind regards.

1 Like
#6

May I add another question?

Why is the efficiency shown only for output current down to 10mA? What happens for lower currents?
I have more precisely estimated the consumption of my system, which is battery-powered (2s1p Li-Ions battery pack, 7.2V nominal voltage, usable voltage range 6-8.2V); the MP2313 is used to generate the 3.3V digital power. The max output current is less than 500mA, and when the system goes into standby, the current consumption goes down to 1mA; which is the efficiency in such condition?
Do you think another of your part number is more suitable for this kind of application?

Thank you! Kind regards.