MP2667: Vin_Fault

Battery Management
1

Hi,
I’m using MP2667 in multiple project that are going soon into production.
One of them:
AC-Supply using MP176A
Battery charger using MP2667
A battery on the Batt pin’s
A Super cap on the VSys
By making some final Software tests, we have a problem with detection of mains failure.

Vin_Min is set to 4.76V, Iin_Lim to 993mA.
It seems to works fine, except detecting mains power failure.
We are reading the Vin_Fault, expecting it to switch to “1” if mains is failing.
This also seems to work if battery is connected in application.

BUT in case there is no battery:
We disconnect Mains supply
→ Vin goes rapidly down
→ Vsys is still high (thanks to SuperCap
But Vin_Fault bit is still reading “0”…

How to get around this?
Reading PG_STAT bit is NOT satisfying, as the VSys voltage decreases too slowly due to SuperCap

P.S.: SuperCap can NOT be connected on Batt pin, as it will not discharge battery even if in transport mode.

Thanks in advance,
Alexandre

2

Hi,
For same project, I also would like to know which is reliable way to detect if battery is present or not by reading data’s out of MP2667.
The battery we are using has no NTC, and is not connected directly to processor. So we can only get this information by I2C.

Thanks in advance,
Alexandre

3

Hi a.ramirez,

Thanks for posting on the MPSNow Forum.
I believe what your asking is that you are not detecting a fault when your Vin falls below the set Vin minimum correct?

Please attach your schematic, as well as scope captures on IN, INT, VDD, SYS.

Thanks,
Cindy