Step-up Dc-dc Converters With Precise, Adaptive Current Limit For Gsm Integrated Products

The MAX1687 MAX1688 Step-up DC-DC Converters deliv- er up to 2W from a single Li-Ion or three NiMH cells. The devices are ideal for burst-load applications such as GSM cell phones and Wireless LANs, where the RF Power Amplifiers require short, high current bursts. The MAX1687 MAX1688 reduce battery surge current by slow- ly charging a reservoir capacitor, which supplies the nec- essary peak energy for the load current burst. As a result, the peak battery current is limited, thus maximizing battery life and minimizing battery voltage sag and transient dips. An internal synchronous Rectifier provides over 90% con- version efficiency and eliminates the need for an external Schottky Diode A Logic shutdown mode reduces the shut- down current to only 3A. The devices CAN be disabled during current bursts (RF transmit mode) to eliminate switching noise. The switching frequency of the MAX1687 MAX1688 con- trolled by the selected inductor, CAN exceed 1MHz. Two external resistors set the output voltage from 1.25V to 6V. The MAX1687 controls peak battery current, while the MAX1688 features a more advanced, adaptive constant- recharge-time algorithm that maximizes battery life. The MAX1687 MAX1688 are available in thin 16-pin TSSOP (1.1mm max height) or standard 8-pin SO packages. By Maxim Integrated Products