The Texas Instruments UC3909QTR is a battery charge controller, designed to manage the charging profile for lead-acid or similar battery chemistries in a single IC. It handles the voltage and current regulation loop, charge termination, and status indication — essentially the brains of a smart charger. You will find this part in industrial power supplies, UPS systems, battery backup units, and any equipment where a sealed lead-acid battery needs a controlled charge cycle.
Lifecycle and compliance — the sourcing reality
The product status is Active. This part is RoHS non-compliant.
As a charge controller, the UC3909QTR does not have a single headline rating like a voltage or current output — its value is in the control algorithm. It implements a multi-stage charge profile (bulk, absorption, float) and includes temperature compensation if you connect an external thermistor. That means the external pass transistor (typically a MOSFET or Darlington pair) and the current-sense resistor are what actually set the charge current and voltage; the UC3909QTR just drives the gate. For a BOM planner, that translates to: you need at least one power transistor, one sense resistor, and a few passive components to make it work. The controller itself draws minimal quiescent current, so the thermal design is about the pass element, not the IC.
The package is Bulk.