Garmin MC34676B - Manual

© Freescale Semiconductor, Inc., 2009. All rights reserved.
Freescale Semiconductor
User’s Guide Document Number: KT34676BUG
Rev. 1.0, 2/2009
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 85 o C, and a 1.0% constant voltage
accuracy over -40 to 85 o C. A charge current thermal
foldback feature, limits the charge current when the IC
internal temperature rises to a preset threshold.
Using the High Input Voltage Charger for
Single Cell Li-Ion Batteries
(KIT34676EPEVBE)
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