Data Sheet

REV 1.1 6
Detailed Description
The CN3083 is a linear battery charger designed primarily for charging single cell lithium-ion or
lithium-polymer batteries. Featuring an internal P-channel power MOSFET, the charger uses a
constant-current/constant-voltage to charge the batteries. Continuous charge current can be programmed up to
600mA with an external resistor. No blocking diode or sense resistor is required. The on-chip 8-bit ADC can
adjust charging current automatically based on the output capability of input power supply, so CN3083 is ideally
suited for the solar-powered systems, or the applications that need to charge lithium-ion battery or lithium
polymer battery with an input power supply whose output capability is limited. The open-drain output OK and
CH
indicates the charger’s status. The internal thermal regulation circuit reduces the programmed charge current
if the die temperature attempts to rise above a preset value of approximately 115℃. This feature protects the
CN3083 from excessive temperature, and allows the user to push the limits of the power handling capability of a
given circuit board without risk of damaging the CN3083 or the external components. Another benefit of
adopting thermal regulation is that charge current can be set according to typical, not worst-case, ambient
temperatures for a given application with the assurance that the charger will automatically reduce the current in
worst-case conditions.
The charge cycle begins when the voltage at the V
IN
pin rises above the UVLO level, a current set resistor is
connected from the ISET pin to ground. The CH pin outputs a logic low to indicate that the charge cycle is
ongoing. At the beginning of the charge cycle, if the voltage at FB pin is below 3V, the charger is in precharge
mode to bring the cell voltage up to a safe level for charging. The charger goes into the fast charge
constant-current mode once the voltage on the FB pin rises above 3V. In constant current mode, the charge
current is set by R
ISET
. When the battery approaches the regulation voltage, the charge current begins to decrease
as the CN3083 enters the constant-voltage mode. When the current drops to charge termination threshold, the
charge cycle is terminated, OK is pulled low by an internal switch and CH pin assumes a high impedance state to
indicate that the charge cycle is terminated. The charge termination threshold is 10% of the current in constant
current mode. To restart the charge cycle, just remove the input voltage and reapply it. The charge cycle can also
be automatically restarted if the FB pin voltage falls below the recharge threshold. The on-chip reference voltage,
error amplifier and the resistor divider provide regulation voltage with 1% accuracy which can meet the
requirement of lithium-ion and lithium polymer batteries. When the input voltage is not present, the charger goes
into a sleep mode, dropping battery drain current to less than 3uA. This greatly reduces the current drain on the
battery and increases the standby time.
The charging profile is shown in the following figure: