MP2607 – LI-ION CHARGER WITH POWER PATH MANAGEMENT
MP2607 Rev. 1.03 www.MonolithicPower.com 13
5/18/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
APPLICATION INFORMATION
COMPONENT SELECTION
Battery Charging Current
The charging current of MP2607 is
programmable using an external resistor R
CHG
at ICHSET pin:
)(Ω
×=
CHG
CHG
R
1.260V
1800I
Where 1.260V is an internal reference voltage
for ICHSET programming. Typically R
CHG
is
chosen between 1.51k (1.50A I
CHG
) and 7.5k
(300mA I
CHG
).
However, due to current limit constraint at the
input source, either adapter or USB port input,
the charging current could be less than above
calculated value if system load demand is high.
MP2607 will always ensure the sum of system
load current and charging current complies with
source current limit, with system load has the
priority. Especially for USB mode, when system
load exceeds the source current limit, charging
is actually stopped and battery is pulled in to
supplement the system load.
When using USB port as input source, if the
charging current is set higher than USB port
current limit I
USB_MAX
, then the real charging
current will not be higher than USB current limit
and could be reduced further if system draws
any load.
End of Charge Threshold Current
The end of charge threshold current is set
internally to be at 10% of I
CHG
:
)(R
1.260V
180I
CHG
EOC
Ω
×=
Where 1.260V is an internal reference voltage
and R
CHG
is the programming resistor at
ICHSET pin.
When the charging current falls below I
EOC
in
CV charge mode, MP2607 will terminate charge,
and latch the status pin to indicate the end of
charge.
Trickle Charge Current
When the battery voltage is below the minimum
battery voltage V
TH_TRKL
(defined in the electrical
characteristics table), the charger operates in a
trickle/preconditioning mode, where the
charging current is typically 7.5% of the
programmed charge current I
CHG
.
)(Ω
×=
CHG
TRKL
R
1.260V
150I
Timer for Charge Termination
MP2607 has a built-in timer to terminate the
charge if the timer times out, no matter whether
I
EOC
is reached or not. And once the battery is
charged full, the timer is reset. This timer is
programmable using an external capacitor C
TMR
at TMR pin, to allow user adjust to different
battery capacity. The timer can be calculated as:
TMR
TMR_F
CHG
C
2 A 1A/36000
1.1hours
2 A I /36000 1 F
μ+
τ= × ×
μ+ μ
The timer period is strictly inversely proportional
to the real charging current (either in power
path state or CV charge mode), the sink and
source current of C
TMR
is
36000/IchgA2 +μ
.
So, the trickle charge timer can be calculated
based on the τ
TMR_F
:
/36000IA2
/36000IA2
2
2
TRKL
CHG
17
15
TMR_FTMR_T
+μ
+μ
××τ=τ
Due to the power path management function,
the real charging current usually varies during
the whole charging process, thus MP2607
automatically takes into account this variation
and adjust the timer time out accordingly.
Basically the timer increases the same
proportion as the charging current decreases. If
the charging is stopped due to high system load,
the timer is temporarily suspended. In this way,
the actual energy delivered to the battery, which
is charging current multiplying the charging time,
remains constant.
The time out operation will set the charger into
suspended state and be reported at the status
output pins. To clear the time out status, one
has to recycle the chip enable pin or IN supply.
