The MAX1535A is a highly integrated, multichemistry battery charger that simplifies construction of advanced smart chargers with a minimum number of external components. It uses Intel's system management bus (SMBus™) to control the charge voltage, charge current, and the maximum current drawn from the AC adapter. High efficiency is achieved through use of a constant off-time step-down topology with synchronous rectification.

In addition to support of the Smart Battery Charger Specifications Rev 1.1, the MAX1535A includes additional features. The maximum current drawn from the AC adapter is programmable to avoid overloads when supplying the load and the battery charger simultaneously. This enables the user to reduce the cost of the AC adapter. The MAX1535A provides a digital output that indicates the presence of an AC adapter. Based on the presence or absence of the AC adapter, the MAX1535A automatically selects the appropriate source for supplying power to the system by controlling two external P-channel MOSFETs. Under system control, the MAX1535A allows the battery to undergo a relearning or conditioning cycle in which the battery is completely discharged through the system load and then recharged.

The MAX1535A is capable of charging 2, 3, or 4 lithium-ion (Li+) cells in series, providing charge currents as high as 8A. The DC-to-DC converter in the MAX1535A uses a high-side P-channel switch with an N-channel synchronous rectifier. The charge current and input current-limit sense amplifiers have low input-offset errors and can use small-value sense resistors (0.01Ω, typ).

The MAX1535A is available in a 5mm x 5mm 32-pin thin QFN package and operates over the extended -40°C to +85°C temperature range. An evaluation kit is available to reduce design time.

Applications

• Notebook and Subnotebook Computers
• Portable Equipment with Rechargeable Batteries
• Tablet PCs