Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 Design-in Page 49 of 119
GND
Power pat h management IC
VoutVin
θ
Li-Ion/Li-Pol
Bat t ery Pack
GND
Syst em
12 V
Primary
Source
Charge
cont roller
DC/DC convert er
and bat t er y FET
cont rol logic
Vbat
Figure 23: Charger / regulator with integrated power path management circuit block diagram
Figure 24 and the parts listed in Table 16 provide an application circuit example where the MPS MP2617H switching
charger / regulator with integrated power path management function provides the supply to the cellular module. At the
same time it also concurrently and autonomously charges a suitable Li-Ion (or Li-Polymer) battery with the correct pulse
and DC discharge current capabilities and the appropriate DC series resistance according to the rechargeable battery
recommendations described in section 2.2.1.4.
The MP2617H IC constantly monitors the battery voltage and selects whether to use the external main primary supply /
charging source or the battery as supply source for the module, and starts a charging phase accordingly.
The MP2617H IC normally provides a supply voltage to the module regulated from the external main primary source
allowing immediate system operation even under missing or deeply discharged battery: the integrated switching step-
down regulator is capable to provide up to 3 A output current with low output ripple and fixed 1.6 MHz switching
frequency in PWM mode operation. The module load is satisfied in priority, then the integrated switching charger will
take the remaining current to charge the battery.
Additionally, the power path control allows an internal connection from battery to the module with a low series internal
ON resistance (40 mΩ typical), in order to supplement additional power to the module when the current demand
increases over the external main primary source or when this external source is removed.
Battery charging is managed in three phases:
• Pre-charge constant current (active when the battery is deeply discharged): the battery is charged with a low current,
set to 10% of the fast-charge current
• Fast-charge constant current: the battery is charged with the maximum current, configured by the value of an
external resistor to a value suitable for the application
• Constant voltage: when the battery voltage reaches the regulated output voltage (4.2 V), the current is progressively
reduced until the charge termination is done. The charging process ends when the charging current reaches the 10%
of the fast-charge current or when the charging timer reaches the value configured by an external capacitor
Using a battery pack with an internal NTC resistor, the MP2617H can monitor the battery temperature to protect the
battery from operating under unsafe thermal conditions.
Several parameters as the charging current, the charging timings, the input current limit, the input voltage limit, the
system output voltage can be easily set according to the specific application requirements, as the actual electrical
characteristics of the battery and the external supply / charging source: suitable resistors or capacitors must be
accordingly connected to the related pins of the IC.