Datasheet

Analog Integrated Circuit Device Data
Freescale Semiconductor 11
34671
FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
The MC34671 is a fully-integrated Li-Ion and Li-Polymer
battery charger in a tiny package. It uses current, voltage and
temperature control loops to regulate the charge current. It
has up to a 28V input voltage rating, which makes the
handheld device safe even when connected to a wrong AC
adapter.
The MC34671 requires only two external capacitors and
one resistor to build a fully functional charger for space-
limited applications such as cell phones, Bluetooth
accessories and MP3 players. Its ultra high-accuracy
(±0.7%) output voltage and temperature-limited charging
current offer additional battery safety during charging.
The CC-mode current can be programmed with an
external resistor (R
ISET
). The voltage across this resistor is
proportional to the charge current, so the system can monitor
the charge current during the whole charge cycle. The EOC
current threshold is preset to 10% of the CC-mode current.
For a deeply discharged battery with a voltage lower than
2.7V, the MC34671 charges the battery with a trickle-mode
current, which is 20% of the CC-mode current.
Three indication outputs make it easy to report the input
power status and the charge status to MCUs, or users via
LEDs.
FUNCTIONAL PIN DESCRIPTION
INPUT SUPPLY (VIN)
The supply input. This pin should be bypassed to ground
with a 1.0µF capacitor.
POWER PRESENT INDICATOR (PPR)
Open-drain logic output to indicate the input-power status.
The
PPR pin output is only determined by the input voltage,
not other conditions such as the
EN pin input. The output is
low if V
IN
is higher than V
POR
. This pin is capable to sink at
least 12.0mA of current to drive an LED indicator.
CHARGE INDICATOR (CHG)
Open-drain logic output to indicate the charge status. The
output is low when the MC34671 is charging, until the EOC
conditions are reached. This pin is capable to sink at least
12.0mA of current to drive an LED indicator.
ENABLE (EN)
Active low enable logic Input. This pin is internally pulled to
ground by a weak current source. When left floating, the
charger is enabled. Pulling this pin to a high voltage,
externally disables the charger.
GROUND (GND)
Ground.
FAST CHARGE INDICATOR (FAST)
When charging, this open-drain logic output indicates
whether or not the battery voltage is higher than the trickle-
mode threshold. This pin is capable to sink more than 0.3mA
of current. When the charger is on, this pin outputs a logic low
signal if the battery voltage is higher than the trickle-mode
threshold. When the charger is in the shutdown mode or in
any fault conditions, this pin outputs a high-impedance.
CC-MODE CURRENT SETTING AND CHARGE
CURRENT MONITOR (ISET)
The CC-mode current, I
CHG
, is programmed by connecting
a resistor, R
ISET
, between this pin and the ground. When
charging in the CC-mode, the voltage at this pin is 1.0V. The
voltage reduces proportionally as the charge current reduces
in the CV-mode. During the whole charge cycle, the voltage
at this pin can be used to monitor the charge current using the
following equation:
equ. 1
where I
BAT
is the actual charge current, I
CHG
is the
programmed CC-mode current, and V
ISET
is the voltage of
the ISET pin during the whole charge cycle.
CHARGER OUTPUT (BAT)
Charger output pin. Connect this pin to the battery being
charged. Bypass to ground with a 2.2µF or higher capacitor.
EXPOSED PAD (EPAD)
Exposed pad. It must be soldered on the large ground
plane of the PCB to enhance the thermal conductivity. The
pad must be connected to GND electrically.
I
BAT
V
ISET
1.0V
---------------
I
CHG
⋅=