NCP1800 ON, NCP1800 Datasheet - Page 10

• Manufacturer Part Number: NCP1800
• Description: Single-Cell Lithium Ion Battery Charge Controller
• Manufacturer: ON

Operation Descriptions
charge controller and provides the necessary control
functions for charging Li-ion batteries precisely and safely.
It features the constant current and constant voltage method
(CCCV) of charging.
Conditioning and Pre-charge Phase
COMP/DIS to LOW or application of the valid external
power source (i.e. V
Li-ion battery present or when the Li-ion battery is inserted.
Before a charge cycle can begin, the battery conditions are
verified to be within safe limits. The battery will not be
charged when its voltage is less than 0.9 V or higher than
V
from a completely discharged state. Also, a fully discharged
Li-ion battery may indicate an abnormal battery condition.
With the built-in safety features of the NCP1800, the Li-ion
battery pre-charges (Pre-Charge Phase) at 10% of the full
rated charging current (I
lower than V
battery voltage reaches V
Full Charge phase begins.
Full Charge (Current Regulation) Phase
begins fast charging the battery with full rate charging
current I
at the I
sense resistor, R
at I
phase.
formula:
SOVLO
The NCP1800 is a linear lithium ion (Li-ion) battery
The NCP1800 initiates a charging cycle upon toggling the
Li-ion batteries can be easily damaged when fast charged
When the battery voltage reaches V
I
And with R
REG
REG
SNS
is determined by R
.
REG
by the pass transistor throughout the full charge
input pin by the voltage drop across a current
PCTH
. The NCP1800 monitors the charging current
ISEL
SNS
I REG +
and the CFLG pin is HIGH. Typically, the
= 60 k and R
, and the charging current is maintained
UVLO
PCTH
REG
(R ISEL
SNS
(1.19
t V
) when the battery voltage is
and R
in a few minutes and then the
SNS
CC
12 k)
R SNS)
ISEL
= 0.4 W, I
t V
PCTH
with the following
OVLO
, the NCP1800
REG
) with the
= 0.6 A.
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NCP1800
10
the current to charge the battery and operates in linear mode
as a linear regulator, power is dissipated in the pass
transistor. Designing with a very well regulated external
adaptor (e.g. 5.1 V 1%) can help to minimize the heat
dissipation in the pass transistor. Care must be taken in heat
sink designing in enclosed environments such as inside the
battery operated portables or cellular phones.
reaches V
V
Final Charge (Voltage Regulation) Phase
is controlled to regulate the voltage across the battery and the
Final Charge phase (constant voltage mode) begins. Once
the charger is in the Final Charge phase, the charger
maintains a regulated voltage and the charging current will
begin to decrease and is dependent on the state of the charge
of the battery. As the battery approaches a fully charged
condition, the charge current falls to a very low value.
Trickle Charge Phase
continues to decrease and the NCP1800 monitors the
charging current through the current sense resistor R
When the charging current decreases to such a level that I
< 0.1 X I
Charge phase begins. The charger stays in the Trickle
Charge phase until any fault modes are detected or the
COMP/DIS pin is pulled low to start over the charging cycle.
REG
Since the external P channel MOSFET is used to regulate
The Full Charge phase continues until the battery voltage
Once the battery voltage reaches V
During the Final Charge phase, the charging current
thresholds of 4.1 and 4.2 V.
REG
REG
, the CFLG pin is set to LOW and the Trickle
. The NCP1800 comes in two options with
REG
, the pass transistor
SNS
SNS
.