Electronic Design

Battery-Charger ICs Provide Instant-On Capability

The latest member of the SMB339 family of battery-charger ICs from Summit Microelectronics, the SMB329, integrates additional features such as instant-on even with a dead battery and real-time charge current monitoring. Like its predecessors, the third-generation device’s parameters are programmable in nonvolatile memory for power-up configuration and in volatile memory for in-system adjustments via the I2C host interface.

In addition, the SMB329’s high-efficiency switch-mode operation and TurboCharge mode allow for 30% to 50% shorter charging times while reducing thermal dissipation and wasted power by 80%. It supports all relevant interface (USB 2.0, USB OTG, USB charging, etc.) and safety (IEEE1725, JICS8714, etc.) standards, reducing the development time and cost associated with system compliancy efforts. Its universal USB charging eliminates electronic waste and reduces energy use as well.

The SMB329 is based on a 3-MHz switch-mode architecture with minimal external components, allowing for very efficient power delivery and extremely compact solution size, according to Summit. Its high-efficiency operation enables fast charging due to higher output/charge currents while reduced thermal dissipation improves user comfort and system reliability. The patent-pending TurboCharge technology enables high charge current, even from relatively low-power sources—for example, up to 750-mA output from a 500-mA USB source.

As consumer devices continue to employ larger batteries, the SMB329 reduces charge time for consumer convenience. It provides the means to accomplish true, universal USB charging and to meet the various USB industry standards without the need for additional hardware and software support, Summit says. In addition, it provides instant-on power from the input source to critical system components, allowing them to wake up and perform system functions even with a deeply discharged (dead) or missing battery. Its integrated instant-on operation improves customer convenience without the cost and size penalty of alternate implementations.

Furthermore, the SMB329 allows the host to directly measure charge current in real time, enabling the system to recognize the operating mode it is in and make necessary adjustments for increasing battery life, monitoring for safety and communicating information to the user. Its patent-pending power-source detection and automatic input current limit ensure that the charge current is safely and dynamically optimized regardless of power-source capability (USB or ac-dc). The improved user experience translates into fewer service calls, fewer merchandise returns, and increased subscriber revenue for wireless carriers.

The SMB329 supports USB On-the-Go (OTG) with integrated VBUS power without additional components or cost. Its step-down converter, which normally operates in “forward mode” to charge the battery, can operate in reverse to boost the battery voltage to +5 V for USB OTG and deliver up to 500 mA, exceeding the USB OTG Supplement Specification requirements. USB-OTG allows two portable USB devices to connect to and/or power each other without a host PC, creating unlimited opportunities for mobile connectivity such as exchanging media files between portable devices and charging Bluetooth headsets from a mobile phone.

Also, the SMB329 supports existing and emerging safety standards (IEEE1725, JISC8714, and others) for portable devices. Its safety features include input/output current limits, input and battery overvoltage protection, battery and chip thermal protection, charge safety and watchdog timers, trickle charging, and status/fault monitors. In addition, the chip’s parametric programmability enables the implementation of sophisticated embedded charging algorithms, further increasing system performance and reliability.

Summit also offers the SMB329EV evaluation board and GUI software so designers can quickly see the chip’s features and benefits and use it to design a prototype battery-charging solution. According to the company, this complete development tool lets designers easily manipulate the characteristics of their systems. The kit includes menu-driven Microsoft Windows GUI software to automate programming tasks as well as all necessary hardware to interface to a PC’s or laptop’s USB port.

Once a user completes design and prototyping, the SMB329EV automatically generates a HEX data file that can be transmitted to Summit for review and approval. Summit then assigns a unique customer identification code to the HEX file and programs the customer’s production devices prior to final electrical test operations. This ensures that the device will operate properly in the end application.

The SMB329 operates from 3.5 to 6.2 V input and safely withstands continuous input overvoltage up to 18 V (non-operating) while protecting downstream circuitry. It comes in a 2.3- by 2.0-mm, 20-ball, lead-free chip-scale package (CSP) and in a 4- by 4-mm QFN-24 (quad flat no-lead) package, both with an operating temperature range of –30°C to 85°C. Available now in production quantities, it costs $1.15 in lots of 10,000.

Summit Microelectronics


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