Maxim’s new MAX8989 step-down converter is designed to power PA (power amplifier) modules in mobile phones. Said to be the first DC-DC converter in the industry to support power management for multiple communication protocols (e.g., LTE, WCDMA, GSM, and EDGE), the MAX8989 is well suited for converged (multimode) PAs.
The MAX8989 integrates a high-efficiency switching regulator with a parallel bypass LDO for optimum efficiency under all conditions. This approach enables designers to minimize the amount of power dissipated within the PA by regulating the PA’s output stage supply voltage. By controlling the PA supply voltage to meet transmission-power requirements, designers can extend 2G talk time by up to 25% and 3G talk time by up to 10%, according to the company.
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The integrated LDO serves to smooth the transition between step-down regulation and operation in dropout, allowing for a seamless transition to higher power levels. When in dropout, the LDO becomes a low-impedance (85mΩ) bypass FET to ensure minimal power loss during periods of peak current demand. Additionally, the switching regulator is capable of a 100% duty cycle to further eliminate losses.
The MAX8989 supports up to 2.5A, making it a good choice for powering GSM/EDGE PAs. It is fully specified over the -40°C to +85°C extended temperature range, and offered in a compact (1.6mm × 1.6mm, 0.69mm max height), 9-bump wafer-level package (WLP). Prices start at $1.92 (1000-up, FOB USA).