Maxim's new DC-DC converter aims to provide a power solution for multimode PA modules, which would allow designers to extend battery life and talk time in mobile handsets.

Maxim Integrated Products has introduced the MAX8989, a step-down converter designed to power the power-amplifier (PA) modules in mobile phones. As the first DC-DC converter to support power management for multiple communication protocols (e.g. LTE, WECDMA, GSM, and EDGE), Maxim believes that the MAX8989 is ideal for converged (multimode) PAs (see the figure). This solution is utilized in Infineon’s SMARTi UE2 RF engine platform, which delivers flexibility and efficiency to multistandard cellular phone systems.

The MAX8989 integrates a high-efficiency switching regulator with a parallel bypass low-dropout regulator (LDO) to guarantee maximum 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%.

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The integrated LDO will serve to smooth the transition between step-down regulation and operation in dropout, allowing for a smooth transition to higher power levels. When in dropout, the LDO becomes a low-impedance (85 mΩ) bypass field effect transistor (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 2.5 A, so it can power GSM/EDGE PAs. It is fully specified over the -40°C to +85°C temperature range, and offered in a compact (1.6 mm × 1.6 mm, 0.69 mm max height), nine-bump wafer-level package (WLP). Prices start at $1.92 (1000-up). Samples and evaluation kits are available upon request.

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