Maxim Integrated Products Inc. (Sunnyvale, CA) unveiled its new MAX1551 and MAX1555 USB/ac-adapter, single-cell, lithium-ion (Li-Ion), 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, and other hand-held products.
The MAX1551 and 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 (maximum), which 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 (typical). No input-blocking diodes are required to prevent battery drain.
The MAX1551 includes a power-OK output to indicate when input power is present, and the MAX1555 includes a charge 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 guard-banding. When the MAX1551/MAX1555 thermal limit is reached, the charger reduces charging current instead of shutting down.
The MAX1551 and MAX1555 are available in a five-pin SOT23 package and are screened for the extended industrial temperature range of -40°C to +85°C. An evaluation kit is available to speed designs.
