Datasheet

Analog Integrated Circuit Device Data
Freescale Semiconductor 17
34671
TYPICAL APPLICATIONS
INTRODUCTION
TYPICAL APPLICATIONS
INTRODUCTION
INPUT CAPACITOR
The input capacitor is used to reduce the input voltage
transient that may cause instability. A 1.0µF, X5R, 16V-rated
ceramic capacitor is recommended for most applications.
OUTPUT CAPACITOR
For stable operation, an X5R ceramic capacitor with a
minimum 2.2µF 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, R
ISET
. A 1% accuracy resistor is recommended to
guarantee 5% a 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
R
DS(ON)
is 700mΩ. The input voltage should be at least
higher than V
BAT
+ I
CHG
x 700mΩ to guarantee the
programmed CC-mode current.
THERMAL CONSIDERATIONS
The MC34671 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
MC34671 to charge the battery with the maximum current,
while minimizing the die temperature.
APPLICATIONS
STAND-ALONE CHARGER
The MC34671 can be used in a stand-alone 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.
Figure 23. Standalone Li+ Battery Charger
VIN
GND
ISET
BAT
CHG
PPR
FAST
EN
Input
REDGREEN
1µF 2.2µF
Li+
5.23k
470470
MC34671