March 19, 2012 – Linear Technology Korea (CEO Hong Sa-gwak) announced the development of the LTC4156, a high-power, I2C-controlled, high-efficiency PowerPath™ manager and ideal diode controller, as well as a LiFePO4 (Lithium Iron Phosphate) battery charger. This product is used in single-cell devices such as portable medical and industrial equipment, backup systems, and other high-power-density battery-driven applications. The IC efficiently delivers up to 15W of power from various sources while minimizing power consumption and reducing thermal constraints. The LTC4156's switching PowerPath topology manages smooth power distribution from two input sources—such as wall outlets and USB ports—to the device's LiFePO4 battery for charging, and prioritizes power delivery to the system load when input power is limited.
Because power is conserved in the LTC4156, the output load current can exceed the current drawn from the input supply, thereby maximizing available power for battery charging without exceeding the input supply power specification. For example, when powered from a 5V/2A adapter, the IC's switching regulator efficiently delivers over 90% of the available 10W, providing a maximum charging current of 2.4A and reducing charge time. Unlike other conventional switching battery chargers, the LTC4156 features instant-on operation that enables system power to be available when plugged in, even with severely depleted batteries. USB OTG (On-the-Go) support provides a 5V supply back to the USB port without any additional components.
A simple two-wire I2C port provides extensive control of many system parameters, including charge current, input current (USB 2.0 and 3.0 compatible settings), and float voltage (3.45V/3.55V/3.60V/3.80V). The LTC4156 also provides status information via the communication bus, including battery temperature, input supply status, charger status, and fault conditions.
The LTC4156's automatic full-featured single-cell LiFePO4 battery charger supports a maximum charging current of 3.5A and features 15 charge current settings. The charger offers functions including automatic recharge, bad cell detection, safety timer (programmable), thermistor temperature-based charging, full-charge indication/termination, and interrupt generation (programmable).
The LTC4156's dual-input, priority multiplexing OVP (overvoltage protection) circuit prevents damage that could result from sudden application of high voltage. The ideal diode controller ensures that sufficient power is always available at the output voltage when input power is insufficient or absent. When the device is connected to a suspended USB port, an LDO between the bus voltage and output voltage provides an application-permissible USB suspend current to minimize battery depletion. Additionally, a ship-and-store function is provided to prevent battery depletion during manufacturing and distribution, reducing the already-low battery standby current to nearly zero. The LTC4156 is a complementary product to the LTC4155, offering equivalent functionality for lithium-ion/polymer battery-based systems.
The LTC4156 is available in a low-profile (0.75mm) 28-pin 4mm x 5mm QFN package, with guaranteed operating performance over the temperature range of -40°C to 125°C. Pricing starts at $4.07 per unit in quantities of 1,000. For detailed product information, refer to www.linear.com/product/LTC4156.

Photo Caption: High-efficiency I2C Power Manager with OVP and USB OTG functionality and 3.5A LiFePO4 battery charger

Product Features: LTC4156
• High-power, high-efficiency switching LiFePO4 battery charger with 3.5A charging current capability
• Monolithic switching regulator optimizes limited input power utilization
• Dual-input overvoltage protection controller
• Priority multiplexing capability for multiple inputs
• I2C/SMBus control for optimal system performance and status information
• Instant-on operation when battery power is low
• Battery ideal diode controller for power management
• USB OTG power delivery from battery to USB port
• Full-featured lithium iron phosphate charger with four float voltage settings (3.45V/3.55V/3.60V/3.80V)
• Maximum charging current of 3.5A from adapter
• USB 2.0 and USB 3.0 specification support
• Low-profile (0.75mm) 28-pin 4mm x 5mm QFN package