Power management components for Li-ion battery powered applications

Feature Story

Power management components for Li-ion battery powered applications

Find what Richtek can offer to maximize your design experience from our selected product portfolio for Li-ion battery powered applications.

Designing applications with Li-ion batteries

Li-Ion batteries have several advantages when compared with other battery types:
They are light weight, have twice the energy density and 6 ~ 8 times less self-discharge compared to nickel-cadmium. Li-Ion batteries have no memory effect, and the high cell voltage of 3.6 volts is often sufficient to power applications from a single cell.

Single Li-Ion cell as power source

When powering your application from a single Li-Ion cell, the application input range must consider the voltage fluctuation of the battery, which for most Li-Ion batteries ranges from 4.2V fully charged down to 3.0V fully discharged. Most applications will require some form of voltage regulation. Richtek offers a wide range of LDOs, buck, boost and buck-boost converters that can operate within this input voltage range.

Low Iq LDOs can be used to regulate the output voltage for micro power applications with minimal battery loading. Most low voltage buck converters will operate in 100% duty-cycle mode when battery voltage approaches the output voltage, increasing the useful battery range. Boost converters like RT9276 will produce a stable 5V supply at varying battery voltage and provide battery monitoring function. Buck-boost regulators like RT6150A or RT6154A can be used when the output voltage lies in between the battery max and min voltage range, and they seamlessly switch over from buck to boost mode. Most switching regulators have enhanced light load efficiency, thereby increasing the battery span. (find more Richtek products)

Battery charging

Charging Li-Ion cells needs special care, as overcharge can lead to unsafe conditions. Most Li-Ion chargers have pre-conditioning - constant current - constant voltage - current cut-off functionality.

Battery gauge

Richtek has a wide range of Li-Ion chargers from linear to switching types. Linear charger topology is often used with batteries up to 1000mAh, while switching chargers are used for larger capacity batteries which can be charged with higher currents (>1A), or when using adapters with higher output voltage.

RT9525 is a linear charger with Auto Power Path, which allows the application to be run from adapter power during charging, but it will gradually move back to battery power when the adapter input current limit is exceeded. RT9525 also contains many protection features like input overvoltage protection, output short protection and load disconnect function. (find more linear charger products)

RT9451 is a switching charger with I²C control, which allows flexible selection of charging conditions and system control. Switching topology allows up to 12V input and 4A fast charging current in Buck mode, and the switching MOSFETs can also be set in boost mode where a stable 5V can be supplied from battery to the Vin pin for powering USB-on-the-Go devices. RT9451 is often used for larger capacity Li-Ion batteries (> 2Ah). (find more switching charger products)

Single Li-Ion cell as power source

In many battery applications it is important to know how much charge is left in the battery. Checking the state of charge (SOC) of Li-Ion cells is often done by coulomb counting method, which measures the battery current over time and determines the SOC from the net increase / decrease in charge. These methods are accurate in theory, but suffer from accumulation errors over time, and the circuit is complicated due to the current sense circuit.

An alternative way to determine the SOC is to using a dynamic voltage based fuel gauge, which measures the battery voltage over time, and uses the dynamic voltage measurements in combination with a battery model to calculate the SOC. This topology does not suffer from error accumulation, and is used in RT9420 and RT9428 battery gauge IC’s. (read more)

For more information, please see the landing page “Power management components for Li-ion battery powered applications” and the application note AN025_EN for full text article.

New Products

RT9480 is a highly integrated single chip portable power bank solution for charging or powering other portable devices. It features a 2.5A Boost powering a dual USB output and includes a 1.2A linear charger with temperature sensing and a charge status indication. (read more)

RT8092 is a 4A 3MHz I²C controlled buck converter. The powerful I²C interface can be used to control internal parameters.4A current capability together with the high switching frequency makes it ideal for powering core supplies in portable applications.

RT2657BQ is an AEC-Q100 automotive qualified 0.6A, 2.25MHz low voltage Buck converter, ideal for car audio, Information and navigation applications.

RT9074 is a 60V/100mA LDO with fixed or adjustable output voltage. The low 30μA I_Q, reverse current and 60V reverse voltage protection makes it a great choice for industrial and automotive applications.

Did you know…?

You can find Richtek products via Element14.
Richtek provides power solutions for Intel’s latest IMVP8 Platforms. Please contact us for more information.