Other Parts Discussed in Thread: BQ27421-G1, BQ24072
Hello.
I have 2 boards:
1) BQ24075, with 1k5 resistor at Iset and ILim, and 43K at TMR. (also BQ27421-g1),
so the max. charge current is 600mA, pre-charge = 60mA.
Also ~30mA load is turned on when the external power applied.
2) BQ24072, with 1.18k at ILim and 8.87k at Iset (TMR is not connected), so
the max. charge current is 100mA and pre-charge=10mA.
No load after 24072 when the input viltage applied.
According to the datasheet, if the battery voltage is <3.1v? only pre-charge current goes to the battery and when the voltage rise over 3.1v - full (max.) charge current occurs.
The problem with 24075 is that in this condition, pre-charge current 60mA is only 4 seconds after applying the external power supply. After 4s, the battery current drops to 0.
I played with TMR resistor (43k / connect to GND / not connected) - nothing was changed.
If i put the same resistor as in 072 boad to 075 - pre-charge current is 10mA but also drops after 4 sec.
What to do? Is is a bug inside 24075 or my fault?
This is the part of the schematic:
something?