MP2607 – LI-ION CHARGER WITH POWER PATH MANAGEMENT
MP2607 Rev. 1.03 www.MonolithicPower.com 11
5/18/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
OPERATION
The MP2607 is a highly-integrated single-cell
Li-ion or Li-polymer battery charger with system
power path management function. The full
function charger features trickle charge, high
accuracy constant current (CC) and constant
voltage (CV) regulation, charge termination,
auto recharge, thermal fold-back, built-in timer
and 4-status indicator output. The power path
function allows the input source to power the
system and charge the battery independently. If
there is conflict to meet both system load and
battery charging current, MP2607 will
automatically reduce charging current or even
use battery as supplement to satisfy the system
load. This allows optimal battery charging,
reduces charge/discharge cycle, and best
preserves the battery energy.
Input Selection for Power Path and Charger
MP2607 identifies the input source (IN) based
on the logic level of MODE pin. MODE pulled
high indicates IN is connected with AC adapter,
low indicates IN connected with USB port. In
either case, the input source will supply both
system load and battery charging current. If IN
is not connected to a valid input source, the
battery (BATT) is selected to supply the system
(SYS). The built-in N-channel 50mΩ switch
between BATT and SYS minimizes the
conduction drop and extends the battery life.
The IN of MP2607 can accept voltage as high
as 13V, thus allows the use of low cost high
output ripple adapters.
MODE pin is default “high” with internal pull-up.
Power Path Management
If IN is connected with AC adapter, MP2607
regulates the SYS pin voltage at about 5V with
an internal low drop-out regulator. If IN is
connected with USB port, SYS is connected to
IN through an internal current limited switch. In
both cases, the battery charging is done
through a P-channel FET between IN and
BATT, so the input source supplies both load
current to SYS and charging current to BATT.
This P-channel FET on-resistance is designed
to be less than 0.3ohm to minimize the dropout
from IN to BATT. If the sum of SYS load current
and BATT charging current will exceed the
source current limit, either AC adapter or USB
port, MP2607 automatically reduces the
charging current to comply with the source
current limit and satisfy SYS load demand (Fig2
and Fig3). For USB mode, if SYS load current
further increases beyond the source current
limit, SYS voltage will drop to below BATT and
MP2607 will turn on the 50mΩ N-channel
switch between BATT and SYS to allow battery
to supplement the system load (Fig3). The
control of this switch has two phases in this
battery supplement mode: 1) constant V
DS
where its voltage drop is regulated. This occurs
at low battery supplement current level; 2)
constant R
DS
where the switch is fully on. This
occurs at medium to high battery supplement
current level; Battery supplement mode ensures
the system load is always met and its operation
will not be disturbed.
The constant V
DS
control is enabled only when
IN is connected to a valid source, thus allow
automatic turn-off of the N-channel switch to
avoid overcharge when SYS pin voltage
recovers to rise above BATT pin voltage.
AC adaptor
current Limit
AC adaptor
Voltage
4.3V
Charging
current
AC adaptor
current
SYS load
current
Figure 2—Power Path Management for AC
Adapter Mode
