MP2619 – 2A, 24V INPUT, 600kHz 2-3CELL SWITCHING LI-ION BATTERY CHARGER
MP2619 Rev. 1.01 www.MonolithicPower.com 11
5/28/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
OPERATION
The MP2619 is a peak current mode controlled
switching charger for use with Li-Ion batteries.
Figure 1 shows the block diagram. At the
beginning of a cycle, M1 is off. The COMP
voltage is higher than the current sense result
from amplifier A1’s output and the PWM
comparator’s output is low. The rising edge of the
600 kHz CLK signal sets the RS Flip-Flop. Its
output turns on M1 thus connecting the SW pin
and inductor to the input supply.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier A1.
Ramp compensation is summed to the output of
A1 and compared to COMP by the PWM
comparator.
When the sum of A1’s output and the Slope
Compensation signal exceeds the COMP voltage,
the RS Flip-Flop is reset and M1 turns off. The
external switching diode D1 then conducts the
inductor current.
If the sum of A1’s output and the Slope
Compensation signal does not exceed the COMP
voltage, then the falling edge of the CLK resets
the Flip-Flop.
The MP2619 have one internal linear regulators
power internal circuit, VREF33. The output of
3.3V reference voltage can also power external
circuitry as long as the maximum current (30mA)
is not exceeded. A 1uF bypass capacitor is
required from VREF33 to GND to ensure stability.
Charge Cycle (Mode change: Trickle CC
CV)
The battery current is sensed via RS1 (Figure 1)
and amplified by A2. The charge will start in
“trickle charging mode” (10% of the RS1
programmed current I
CC
) until the battery voltage
reaches 3.0V/cell. If the charge stays in the
“trickle charging mode” till “timer out” condition
triggered, and the charge is terminated.
Otherwise, the output of A2 is then regulated to
the level set by RS1. The charger is operating at
“constant current charging mode.” The duty cycle
of the switcher is determined by the COMPI
voltage that is regulated by the amplifier GMI.
When the battery voltage reaches the “constant
voltage mode” threshold, the amplifier GMV will
regulate the COMP pin, and then the duty cycle.
The charger will then operate in “constant voltage
mode.”
Automatic Recharge
After the battery has completely recharged, the
charger disables all blocks except the battery
voltage monitor to limit leakage current. If the
battery voltage falls below 4.0V/Cell, the chip will
begin recharging using soft-start. The timer will
then reset to avoid timer-related charging
disruptions.
Charger Status Indication
MP2619 has two open-drain status outputs:
CHGOK and ACOK . The ACOK pin pulls low
when an input voltage is greater than battery
voltage 300mV and over the under voltage
lockout threshold.
CHGOK
is used to indicate the
status of the charge cycle. Table 1 describes the
status of the charge cycle based on the
CHGOK and ACOK outputs.
Table 1Charging Status Indication
ACOK
CHGOK
Charger Status
low low In charging
low high
End of charge, NTC
fault, timer out, thermal
shutdown,
EN disable
high high
PIN –V
BATT
<0.3V.
AIN<UVLO,
Timer Operation
MP2619 uses internal timer to terminate the
charge if the timer times out. The timer duration
is programmed by an external capacitor at the
TMR pin.
The trickle mode charge time is:
0.1uF
C
30minsT
TMR
TICKLE_TMR
The total charge time is:
0.1uF
C
3hoursT
TMR
TOTAL_TMR
