8/18/2003
Edited by PETech Staff
Dual-input, USB/AC-Adapter, Li+ Chargers
Maxim Integrated Products’ MAX1551/MAX1555 are one of the first USB/AC-adapter, single-cell Li-ion (Li+) battery chargers in an SOT23 package. The USB-charging feature enables users to forgo carrying a wall cube for charging and is particularly attractive for use with PDAs, cell phones, digital still cameras, MP3 players, numerous other handheld products. The MAX1551/MAX1555 accept operating input voltages up to 7V and don’t require external FETs or diodes. When USB power is connected without dc power, the charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs, with no port communication required. When both dc and USB power are connected, charging current is set at 340mA (typ). No input-blocking diodes are required to prevent battery drain.
The MAX1551 includes a power-OK (POK-bar) output to indicate when input power is present, and the MAX1555 includes a charge (CHG-bar) output to indicate charging status. On-chip thermal regulation simplifies PC-board layout by regulating charge current based on charger die temperature. This maximizes charge rate and minimizes component-size guardbanding. When the MAX1551/MAX1555 thermal limit is reached, the charger reduces charging current instead of shutting down.
The MAX1551/MAX1555 are available in a tiny 5-pin SOT23 package and are screened for the extended industrial temperature range (-40°C to 85°C). An evaluation kit is available to speed designs.
For more information, visit www.maxim-ic.com.