Linear Technology Launches 15W I2C Power Manager
Charges Li-ion cells at 3.5A for tablets, UMPCs and portable power systems

June 16, 2011 - Linear Technology Corporation announces the LTC4155, a high efficiency PowerPath™ manager with high power I2C control, an ideal diode controller and a lithium-ion battery charger for single-cell portable devices such as tablet PCs, ultra-mobile PCs (UMPCs), personal video players, smart phones, digital cameras, PDAs, portable medical devices, industrial devices and personal navigation devices. The IC is designed to efficiently deliver up to 15W of power from a variety of sources while minimizing power loss and easing thermal design concerns. The LTC4155’s switching PowerPath topology seamlessly manages power flow from two input sources, such as a wall adapter and USB port, to the device’s rechargeable Li-ion battery while preferentially providing power to the system load when input power is limited.

Because power is conserved, the LTC4155 allows the output load current to exceed the current drawn from the input supply, thus maximizing the available power for battery charging without exceeding the input supply power transfer specifications. For example, when powered from a 5V/2A adapter, the IC's switching regulator can efficiently deliver more than 90% of the available 10W, allowing up to 2.4A of charge current. This, in turn, reduces charge time. Unlike typical switching battery chargers, the LTC4155 also features an instant-on feature to ensure system power when a deeply discharged battery is plugged in. Provides 5V input behind the USB port without any additional components via USB On-The-Go support.

A simple 2-wire I2C port provides extensive adjustment for a variety of system control parameters, including charge current, input current (including USB 2.0 and 3.0 compatible settings), and float voltage. Via the communications bus, the LTC4155 provides status information such as battery information, input supply status, charge status, and fault conditions.
The LTC4155's unique, full-featured single-cell Li-Ion/Polymer battery charger provides up to 3.5A of charge current, features four float voltage settings and 15 charge current settings. For enhanced safety benefits, integrated overtemperature battery conditioning circuitry selectively reduces the battery voltage under both high battery temperature and high battery voltage conditions. The charger also provides automatic charge, fault cell detection, maintenance charge, programmable safety timer, thermistor temperature-qualified charging, programmable charge completion indication/termination, and programmable interrupt generation.

The LTC4155’s dual input, priority multiplexed overvoltage protection (OVP) circuitry prevents catastrophic damage due to high voltages. Its built-in diode controller ensures that sufficient power is always available to VOUT, even when input power is low or absent. To minimize battery drain when a device is connected to a suspend USB port, an LDO that drives the VOUT output from the VBUS input provides only the USB suspend current allowed for the application. To prevent battery drain between manufacturing and shipping, a ship-and-store feature reduces the low battery standby current to zero.