1 Purpose
This User Guide helps the Lithium-Ion (Li-Ion) battery charger designer understand the MC34676B and its evaluation board. It illustrates the design procedure when using the MC34676B to design a Li-Ion battery charger, and the way to get the best performance from the MC34676B.
2 Scope
The 34676 is a dual 28V input voltage and fully-integrated single cell Li-Ion battery charger, targeting smart handheld applications. One of the inputs is optimized for charging with a USB port, and the second is optimized for an AC/DC adapter power source. The charger has two 28V power devices, to eliminate the need of any external power source selection and input over-voltage protection circuitry. Each of the power devices independently controls the charge current from the input, and performs as an independent charger. Only one of the two chargers operate at a time. The AC charger current and the USB charger current are programmable, up to 1.2A and 400mA, with an external resistor respectively. The voltage across the two external resistors is also used to monitor the actual charge current through each charger respectively. The EOC current of both chargers is the same, and programmable by an external resistor. The 4.85V regulator can be used to power a sub-system directly.
The 34676 has a 5% constant current accuracy for the AC Charger over -40 to 85oC, and a 1.0% constant voltage accuracy over -40 to 85oC. A charge current thermal foldback feature, limits the charge current when the IC internal temperature rises to a preset threshold.
Contents
1 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 Application Diagram . . . . . . . . . . . . . . . . . . . 2 4 Evaluation Board Specification . . . . . . . . . . 3 5 Component Selection . . . . . . . . . . . . . . . . . . 4 6 Layout Design . . . . . . . . . . . . . . . . . . . . . . . . 6 7 Evaluation Board Configuration . . . . . . . . . . 9 8 Test Setup with the Evaluation Board . . . . 11 9 Bill of Material. . . . . . . . . . . . . . . . . . . . . . . . 13 10 References . . . . . . . . . . . . . . . . . . . . . . . . . 13
