MC34673 Datasheet, PDF(17/22 Page) Freescale Semiconductor, Inc – High Input Voltage 1.2A Charger for Single-cell Li-Ion Batteries

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MC34673 Datasheet, PDF (17/22 Pages) Freescale Semiconductor, Inc – High Input Voltage 1.2A Charger for Single-cell Li-Ion Batteries

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TYPICAL APPLICATIONS

INTRODUCTION

TYPICAL APPLICATIONS

INTRODUCTION

INPUT CAPACITOR

The input capacitor is used to reduce the input voltage

transient that may cause instability. A 1.0ÂµF, X5R, 16V rated

ceramic capacitor is recommended for most applications.

OUTPUT CAPACITOR

For stable operation, an X5R ceramic capacitor with a

minimum 2.2ÂµF nominal value is recommended at the output.

Depending on the load transient current, larger capacitance

may be required.

CC-MODE CURRENT SETTING

The CC-mode current can be programmed by the external

resistor, RISET. A 1% accuracy resistor is recommended to

guarantee 6% current accuracy.

DROPOUT VOLTAGE

If the DC input voltage is too low, it may not maintain the

programmed CC-mode charge current due to the voltage

dropout over the power MOSFET. The worst case of the

RDS(ON) is 475mâ¦. The input voltage should be at least

higher than VBAT + ICHG x 475mâ¦ to guarantee the

programmed CC-mode current.

THERMAL CONSIDERATIONS

The MC34673 is available in a tiny 2x3 thermally-

enhanced UDFN package. A careful thermal design must be

considered. The exposed pad needs to be well soldered to a

large copper ground plane on the component layer. If the

component layer is space limited and does not allow for a

large copper plane, the thermal pad must be connected to

other ground layers through a via array. This allows

MC34673 to charge the battery with the maximum current,

while minimizing the die temperature.

APPLICATIONS

STAND-ALONE CHARGER

The MC34673 can be used in a standalone charger

without MCUs. Figure 23 shows such an application. The

green LED indicates the power presence and the red LED

indicates the charge status. In total, only 7 external

components are required.

Input

GREEN RED

470 470

VIN

BAT

1ÂµF

MC34673

GND

ISET

CHG

PPR

FAST

5.23k

2.2ÂµF

Li+

Figure 23. Stand Alone Li+ Battery Charger

Analog Integrated Circuit Device Data

Freescale Semiconductor

34673

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