Hi all,
I have do a experiment with TPS25940 to make sure it can replace the AP2501(MAXIM CURRENT LIMITED IC) and MAX6776(MAXIM VOLTAGE MONITOR).
I prefer to used the FLTN for the power lost signal to indicated our SSD controller that the power has lost, and let SSD controller begin power lost dealing action. AS the datasheet show me that FLTN will active low when UVLO,OVP,REVERSE or thermal shutdown. However, i found that the REVERSE is not work as I espected. the datasheet show that the REVERSE active should make VOUT-VIN>=10mv, this may not happen, becuase, SSD unexpected power lost only two type.1. AC lost to let DC-5V lost, the DC-5V fall time is about 5ms.2. hotswap, the SSD input power(DC-5V) will falling in serveral uS. these two condition will not reach the VOUT-VIN>=10mV, in other word, the reverse current can not reach 10mv/42mohm=0.238A, as the above two conditions Rload it two small to sink current. so the FLTN not active when real power lost, it only active when VIN fall below UVLO,befor this time point, , the SSD backup capacitor energy has comsume to SSD normal action, not for power lost dealing. the PGOOD is the same, as the MOSFET not shutdown before VIN fall below UVLO. if we adjust the UVLO, as the Vuvlo=0.93Ven, it will make the Ven higher and narrow our VIN range.
Do you have some advise about this, we just want SSD controller know the power lost earlier to save the backup capacitor.
thanks and best regards.
