Part Number: BQ25570
Dear engineers
I had used the bq25570 for servals days. My application needs a very fast response and it is battery-less because I use a capacitor to store the harvested energy. However, the bq25570 charges slowly at the beginning because of the cold start (after cold start, the speed still can't meet my requirement). I decide to try voltage doubler circuit+ supervisor+LDO.
When using bq25570, I set the Vbat_ok_hyst=2.8V, discharge stop threshold(V_bat_ok)=2.2V. When using bq25570, the Vbat_ok pin enables the Vout_EN as soon as the Vbat=2.8V, the Vout will be opened until Vbat discharge to 2.2V where the Vbat will be charged again.
If I using the voltage doubler circuit+ supervisor+LDO, how to realize this function? As I know,the supervisor only monitors one threshold. There is also the window detector which monitor a low and high threshold. Both of them can not provide the function as described. Because the capacitor needs to be charging from 0V initially. For instance, If using a supervisor (2.8V threshold), a LDO(output 1.8V, 2<Vin<5), the supervisor enable the LDO by RESET pin when Vcap rises to 2.8V. As the LDO consumes the energy, the Vcap will drop and lower than 2.5V so that the supervisor disable the LDO immediately. It seems that the Vcap can never discharge to 2.2V. The same things may happen in a window detector. For example, using a window detector(2.2V low threshold, 2.8V high threshold), the LDO will be enabled once the Vdd reaches 2.2V.
To conclude, how to set a window (similar to V_bat_ok,V_bat_ok_hyst) for LDO?
Thanks