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Garmin MC34676B User Manual

Freescale semiconductor user’s guide, 1purpose, 2scope

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© 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