Diodes API9221 - Manual (Page 8)

API9221
CAR/WALL or USB SUPPLY INPUT LITHIUM BATTERY
CHARGER with OVP USB BYPASS and 10mA LDO
API9221
Document number: DS32204 Rev. 2 - 2
8 of 15
www.diodes.com
November 2011
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T
Functional Characteristics
Logic Description
A Logic State Table and diagrams of timing and charge
profile are given at the end of this description.
The battery charge function is disabled when the EN
input is pulled to logic HIGH. This normally requires an
external pull-up resistor connected to the system
microcontroller I/O power supply. The API9221 has an
internal resistor connected from this pin to GND, typically
600k
Ω. In many applications a suitable pull-up resistor
value is 100k Ω. When EN is pulled LOW or left open
circuit, charging is enabled as described below.
There are two open-drain logic outputs, PPR and CHG .
Each of these can use an external pull-up resistor to an
appropriate supply such as the microcontroller I/O
supply, or can be left open circuit. A suitable value is
100k
Ω. Alternatively these can each be used to drive an
indicator LED up to a maximum of 10mA.
The output PPR is LOW when a valid power supply
voltage is present at the VDC input or at the VUSB input,
independent of EN . One of the two input voltages must
be greater than the power-on threshold and less than the
overvoltage protection threshold.
The output CHG is LOW when the battery is charging,
but only until the End-of-Charge (EOC) condition is
reached. Together with other conditions as described
below, the voltage at the battery connection BAT is used
to control the charging current. In the EOC state, CHG
is HIGH to indicate that the charging phase has
completed and the battery voltage has reached 4.2V (±
1%). In this state, the charger remains active and is able
to supply load current and top up the battery as
necessary. CHG may be re-set as described below
under Charge Conditions.
Auxiliary Outputs
The USB_BYP and VDC_LDO outputs are available
independently of the EN input state. This allows a host
controller to power up initially.
USB Bypass, USB_BYP
The output USB_BYP provides power from the USB
input when a valid power supply voltage is present at the
VUSB input. It is current limited to 400mA (nominally). It
is therefore safely limited in current and voltage within
the USB standard.
VDC Low dropout regulator VDC_LDO
This output provides a regulated 4.94V supply, up to
10mA, when a valid power supply voltage is present at
the VDC input.
Charge Conditions
Before charging can begin, one of the two input voltages
must also exceed the battery voltage enough to
overcome the input-output comparator offset. When one
of the supplies satisfies these conditions, and EN is
LOW, charging begins regardless of the state of the other
supply. The valid input conditions are:
for VDC: VPO
R
< VDC < OVP
VDC
and VDC > V
BAT
+VOS
HC
for VUSB: VPO
R
< VUSB < OVP
VUSB
and VUSB > V
BAT
+ VOS
HC
where VPO
R
is the rising power-on threshold voltage,
and VOS
HC
is the rising input offset voltage relative to
V
BAT
. All these threshold voltages have defined
hysteresis.
When the charge current falls below IMIN, CHG goes
HIGH (provided it has an external pull-up). This state is
latched and is not re-set until one of the following events
occurs:
1. EN is driven HIGH and LOW again
2. The active supply is removed and re-applied
3. V
BAT
falls below the re-charge threshold of 3.9V
(nominally)
Note that the outputs, BAT, USB_BYP and VDC_LDO
are reverse current protected. If an external voltage
higher than the supply voltage is connected to one of
these outputs, that output will be disabled.
Charging from Adapter Power (VDC pin)
The battery can be charged from an AC powered wall
adapter or in-car adapter at a current of up to 1.2A using
this input pin. The maximum charge current is set by an
external resistor, R
IVDC
connected between the IVDC and
GND pins. If VDC is greater than the power-on threshold
voltage (VPO
R
) and less than the over-voltage protection
threshold (OVP
VDC
), the battery will begin to charge at a
rate dependent on the battery voltage.
When VDC input is as recommended, (4.5V to 6.7V), no
charge current is drawn from the VUSB input as VDC
takes precedence. Input operation below 4.5V is also
possible, but the charging rate may be affected.
The resistor R
IVDC
determines the charge current
according to
IVDC
R
6820
IVDC = Amp
For example, a resistor value of 13k
Ω sets a charge
current of 0.525A. The recommended IVDC setting is
100mA to 1200mA.