TPS25944L: Difference between nFLT and PGOOD?

Hi James,

Figure 48 in datasheet is block diagram as shown below. Can you confirm if you are pointing out to this figure ?

Yes, that's the figure.  I don't see an time when nFLT would be triggered and PGOOD wouldn't be deactivated, or vice-versa.

HI James,

nFLT and PGOOD are two independent signals. Below are the conditions when these signals assert.

• The nFLT open-drain output is asserted (active low) during undervoltage, overvoltage, reverse voltage-current and thermal shutdown conditions. Additionally, in the TPS25944, the nFLT is asserted when overload condition exists for more than the fault time period (tCB(dly)). The FLT signal remains asserted until the fault condition is removed and the device resumes normal operation. 
• PGOOD is asserted high when internal FET is fully enhanced and PGTH pin voltage is higher than internal reference V(PGTHR).

Hi James,

Does my above reply answer your query ? Do let me know if you have any other questions ?

Hi Praveen,

Thanks for the detailed response.  When any of those fault conditions occur, the output FET will be turned OFF though right?  If that is the case the PGOOD will be deactivated (allowed to be pulled high by external resistor) when any of these faults occur.  Is that correct?

James.

Thanks again Praveen.

As I'm designing this chip into a schematic, it became obvious that I could use the PG output to sequence the power supply startup AND use the nFLT output to to go a micro-controller at a different I/O level for monitoring.  I'll leave that idea for anyone who stumbles across this post.

James.

Good point James.