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Introducing Richtek Switching Chargers -
Key
functions, applications and product portfolio
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Anyone owning a smartphone will agree that longer battery
life and shorter charging times are key features for
portable devices. But do you know what technology is
behind the powerful charging systems in today’s smartphones,
and what are the limiting factors in the quest for ever
faster charging? In order to quickly charge large capacity
batteries in portable devices with power-hungry processors
inside, more powerful chargers are needed. High current
switching chargers in combination with smart adapters
and intelligent control systems make it possible to
set the optimal charge conditions to quickly and safely
charge Li-Ion batteries in a wide range of portable
devices. This feature story explains several application
aspects of switching chargers for single cell Li-Ion
batteries and introduces three switching chargers from
the Richtek Li-Ion charger portfolio:
RT9458 (1.55A),
RT9460 (3A) and
RT9466 (5A).
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A typical Li-Ion charge cycle consists
of a constant current (CC) regulation mode and a constant
voltage (CV) regulation mode. Most energy is transferred
during the CC mode, so higher CC current will reduce
charge time. Standard Li-Ion batteries can be charged
with 0.5C ~ 1C charge currents, where C is the capacity
of the battery. Some batteries can be charged with higher
currents, depending on construction, internal impedance
and temperature.
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Challenges in fast charging:
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Most single Li-Ion cell powered devices are charged
using the USB port which can limit the maximum current.
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High charge currents lead to errors in battery voltage
sense due to resistance in the charge path.
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Maximum allowable temperature of the charger IC
and battery will limit the fast charging current.
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System load during charging will consume some energy
available for battery charging.
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Switching charger ICs need special
functions to deal with input compatibility issues and
optimize battery charging: |
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Smart USB port detection
can determine the maximum available input current.
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Average Input Current Regulation (AICR)
adjusts charge current to the max available input
current.
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Minimum Input Voltage Regulation (MIVR)
avoids overloading the power source.
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IR compensation function
avoids voltage sense errors and extends the CC charge
mode. Click
here for an example without and with IR compensation.
- Battery & Charger IC thermal sense adjusts charging parameters at different temperatures to ensure safe charging conditions.
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Automatic power path function
selects system power source and balances power distribution.
Chick
here to see diagrams of Buck converter charging
paths in different charging scenarios.
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USB on the go (OTG) Boost control
transforms the charging input into a 5V power output.
Programmable OTG current limit allows setting the
USB port output capability.
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Charging with higher input voltage i.e.
9V or 12V reduces input current and
allows higher power transfer. Read more to learn
how this works.
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Introducing three Richtek switching chargers:
RT9458 is a basic switching charger: It
can replace linear chargers to achieve shorter charge
time and better efficiency. It is suitable for Li-Ion
cells up to 1800mAh.
RT9460 is a more advanced switching charger
with wide range input, USB port detection, power path,
NTC sence, suitable for Li-Ion cells from 2500~2800mAh.
RT9466 is a very powerfull 5A swiching
charger with a wide range of features for high current
charging, supporting MTK Pump Express 1.0 and 2.0 for
dynamic input voltage control, to be used with high
capacity cells up to 4000mAh.
• Coming soon:
RT9468 supports Programmable Power
Supply (PPS) capability, which allows optimized switching
charger mode or bypassed charging directly from adapter
to battery using the USB-PD 3.0 communication protocol.
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See more product details on charging parameters,
OTG Boost parameters and protection functions.
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➔ Get your switching charger design started
in no time! |
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Read the full application note "Switching
Battery Chargers" |
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New Products |
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RT9481 is a powerful and easy to
use Power Bank Solution (EZPBS®) in WQFN-24L 4x4
package. RT9481 is a highly integrated single
chip solution with I2C interface including
a 2.7A switching charger with 3A boost output function,
programmable USBOUT Load Switch, BC1.2 Adapter Detection,
DCP controller and a LDO.
⇒
Also see RT9481 Evaluation Board |
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RT9081A is a 500mA, Bias Rail LDO
with Ultra Low Dropout (140mV@500mA) in a small DFN-6L
1.2x1.2mm package. Operates from 0.8V-5.5V
input and 2.4V-5.5V bias rail. Stable with 1µF
Cout, RT9081A regulates both fixed (0.9V-1.8V) & Adj.
(0.8V-3.6V) Vout at 1.5 % accuracy. The low dropout
and good high frequency PSRR makes this LDO very suitable
to derive low voltages supplies like 1.0V or 1.2V from
a low 1.5V voltage intermediate buck rail and a 3.3V
or 5V bias rail. Highly suitable for industrial applications
like Telecom, Enterprise, Server, Medical, etc. |
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