2.5MHz/1.5MHz Step-Down Converters with 60mΩ Bypass in TDFN for CDMA PA Power

The MAX8581/MAX8582 high-frequency step-down converters are optimized for dynamically powering the power amplifier (PA) in CDMA handsets. They integrate a high-efficiency PWM step-down converter for medium- and low-power transmission and a 60mΩ (typ) bypass mode to power the PA directly from the battery during high-power transmission. They use an analog input driven by an external DAC to control the output voltage linearly for continuous PA power adjustment. The MAX8581/MAX8582 use an internal feedback network, and the switching frequency is internally set to 2.5MHz and 1.5MHz, respectively.

Fast switching (up to 2.5MHz) and fast soft-start allowthe use of ceramic 2.2µF input and output capacitors while maintaining low voltage ripple. The small 1.5µH to 3.3µH inductor size can be optimized for efficiency.

The MAX8581/MAX8582 are available in 10-pin, 3mm x3mm TDFN packages (0.8mm max height).

Applications

* WCDMA/NCDMA Cell Phones * Wireless PDAs, Smartphones

* 600mA Step-Down Converter

* 60mΩ (typ) Bypass Mode with Integrated FET

* Dynamically Adjustable Output from 0.4V to VIN

* 2.5MHz and 1.5MHz Switching Frequency

* Small LC Components: 1.5µH to 3.3µH and 2.2µF

* Up to 94% Efficiency

* Low Output Ripple at All Loads

* 2.7V to 5.5V Input

* 0.1µA Shutdown Mode

* Output Short-Circuit Protection

* Thermal Shutdown

* 10-Pin, 3mm x 3mm TDFN Packages