There is this circuit that im trying to understand from a data sheet for an LM3429 Lithuim Ion battery.
The following paragraph is from the data sheet.
"As the battery charges, its voltage begins to rise, and is sensed at the IN pin of the LM3240. Once the battery voltage reaches 8.4V, the LM3420 begins to regulate and starts sourcing current to the base of Q2. Transistor Q2 begins contolling the ADJ. pin of the LM317 which begins to regulate the voltage across the battery and the constant voltage portion of the charging cycle starts. Once the charger maintains a regulated 8.4V across the battery and the charging current is dependent on the state of charge of the battery. As the cells approach a fully charged condition, the charge current falls to a very a low value. "
Im getting confused with when Q2 begins controlling ADJ pin of LM317, how does Q2 have an effect on the LM317, i can get through my head the operation of ADJ as well.
Thanx
The following paragraph is from the data sheet.
"As the battery charges, its voltage begins to rise, and is sensed at the IN pin of the LM3240. Once the battery voltage reaches 8.4V, the LM3420 begins to regulate and starts sourcing current to the base of Q2. Transistor Q2 begins contolling the ADJ. pin of the LM317 which begins to regulate the voltage across the battery and the constant voltage portion of the charging cycle starts. Once the charger maintains a regulated 8.4V across the battery and the charging current is dependent on the state of charge of the battery. As the cells approach a fully charged condition, the charge current falls to a very a low value. "
Im getting confused with when Q2 begins controlling ADJ pin of LM317, how does Q2 have an effect on the LM317, i can get through my head the operation of ADJ as well.
Thanx