San Jose, Calif.—Summit Microelectronics says its SMB135 lithium-ion charger IC, designed to operate with the universal serial bus (USB) and other current-limited power sources, cuts charge time by 66 percent and power dissipation by more than 90 percent compared to traditional linear chargers. Summit touts the device, targeted specifically at single-cell lithium-ion packs, as the world's smallest charger IC as well.
"The SMB135 is a truly ground-breaking product that will enable a new generation of 'ultra-mobile' devices by simplifying the critical battery charging function," says Abid Hussain, director of marketing. The switch-mode device, which can deliver up to 750 mA from a 500-mA USB port (and up to 1 amp from an AC adapter), contains a current-mode buck switching battery charger and fully programmable algorithm (adaptable up to 4.62 volts) for single-cell lithium-ion and lithium-polymer cells. All charging parameters (pre-charge/fast-charge/charge termination current, cell float/pre-charge voltage, battery temperature/timer safety limits), are configurable via a I2C/SMBus interface enabling a wide variety of algorithms without hardware changes. This capability represents more than double the charge current typically available from similarly sized solutions, according to the company. The SMB135 actually measures 1.3-by-1.2 mm, touted the world's smallest for a battery charger IC. Traditional linear charger solutions, says Summit, are typically offered in larger packages to deal with their higher power dissipation characteristics and require extra PCB copper "flood" areas for heat sinking. The chip also provides a 500 mA/100 mA control pin for USB compliance and a STATUS output to drive an
LED (used when the I2C/SMBus is not used for control/monitoring).
The SMB135 can be programmed either dynamically (real-time using volatile registers), by a microcontroller, or statically (pre-programmed using non-volatile registers). In addition, the SMB135's much lower power dissipation cuts the need for thermal current-foldback circuitry, which tends to extend charge time.
The SMB135 integrates over-voltage, short-circuit and
thermal protection circuits. Also the SMB135 protects the battery pack with a programmable battery temperature monitor and charge timers to prevent overcharge conditions. To protect deeply
discharged cells, the SMB135 applies a 3 mA "trickle charge" mode below 2.0 volts.
Click here for additional product information. The SMB135, working over 4.62 to 6 volts and rated for operation over 0 to +70°C, is priced at 98 cents each in 10k units. Summit offers customers the SMB135EV companion evaluation board and a graphical user interface (GUI) software for quickly protoyping a power supply. The design kit software can be downloaded today from the company's web site.
Summit Microelectronics, 1-408-436-9890, www.summitmicro.com