EUP8202-4.2/8.4
OPERATION
and the CHRG pin is forced high impedance. To restart
the charge cycle, remove and reapply the input voltage or
momentarily shut the charger down. Also, a new charge
cycle will begin if the battery voltage drops below the
recharge threshold voltage of 4.05V per cell.
The EUP8202 is a constant current, constant voltage
Li-Ion battery charger controller that uses a current mode
PWM step-down (buck) switching architecture. The
charge current is set by an external sense resistor (RSENSE
across the SENSE and BAT pins. The final battery float
voltage is internally set to 4.2V per cell. For batteries like
lithium-ion that require accurate final float voltage, the
internal 2.4V reference, voltage amplifier and the resistor
divider provide regulation with ±1% accuracy.
)
When the input voltage is present, the charger can be shut
down (ICC =1.5mA) by pulling the COMP pin low. When
the input voltage is not present, the charger goes into
sleep mode, dropping ICC to 10µA. This will greatly
reduce the current drain on the battery and increase the
standby time.
A
10kΩ NTC (negative temperature coefficient)
thermistor can be connected from the NTC pin to ground
for battery temperature qualification. The charge cycle is
suspended when the temperature is outside of the 0°C to
50°C window.
APPLICATIONS INFORMATION
Undervoltage Lockout (UVLO)
An undervoltage lockout circuit monitors the input
voltage and keeps the charger off until VCC rises above
the UVLO threshold (4.2V for the 4.2 version, 7.5V for
the 8.4 version) and at least 250mV above the battery
voltage. To prevent oscillation around the threshold
voltage, the UVLO circuit has 200mV per cell of built-in
hysteresis. When specifying minimum input voltage
requirements, the voltage drop across the input blocking
diode must be added to the minimum VCC supply voltage
specification.
Figure 5.Typical Charge Profile
A charge cycle begins when the voltage at the VCC pin
rises above the UVLO level and is 250mV or more
greater than the battery voltage. At the beginning of the
charge cycle, if the battery voltage is less than the trickle
charge threshold, 2.9V for the 4.2 version and 5V for the
8.4 version, the charger goes into trickle charge mode.
The trickle charge current is internally set to 15% of the
full-scale current. If the battery voltage stays low for 30
minutes, the battery is considered faulty and the charge
cycle is terminated.
When the battery voltage exceeds the trickle charge
threshold, the charger goes into the full-scale constant
current charge mode. In constant current mode, the
charge current is set by the external sense resistor RSENSE
and an internal 100mV reference;
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage
is below the trickle charge threshold, the charger goes
into trickle charge mode with the charge current reduced
to 15% of the full-scale current. If the low-battery
voltage persists for 30 minutes, the battery is considered
defective, the charge cycle is terminated and the
pin is forced high impedance.
CHRG
V
15mV
SNS(TRKL)
I
=
=
TRKL
R
R
V
100mV
SNS(CHG)
I
=
=
Shutdown
CHG
R
R
SENSE
SENSE
The EUP8202 can be shut down by pulling the COMP
pin to ground which pulls the GATE pin high turning off
the external P-channel MOSFET. When the COMP pin is
released, the internal timer is reset and a new charge
When the battery voltage approaches the programmed
float voltage, the charge current will start to decrease.
When the current drops to 25% (4.2 version) or 15% (8.4
version) of the full-scale charge current, an internal
comparator turns off the internal pull-down N-channel
cycle starts. In shutdown, the output of the
pin
CHRG
is high impedance and the quiescent current remains at
1.5mA. Removing the input power supply will put the
charger into sleep mode. If the voltage at the VCC pin
drops below (VBAT + 250mV) or below the UVLO level,
the EUP8202 goes into a low current (ICC = 10µA) sleep
mode, reducing the battery drain current.
MOSFET at the
pin, and connects a weak
CHRG
current source to ground to indicate a near end-of-charge
condition.
An internal 3 hour timer determines the total charge time.
After a time out occurs, the charge cycle is terminated
DS8202 Ver 1.1 Nov.2007
16
EUTECH [ EUTECH MICROELECTRONICS INC ]
