Micrel’s (Nasdaq: MCRL) MIC2807 is a high performance power management IC that provides a complete RF solution for UMTS, EDGE, CDMA2000, and WCDMA handsets. The new device, housed in a tiny 2.5mm x 2.8mm MLF(R) package, provides a total of three outputs; a 2MHz buck regulator and two low noise linear regulators. The device is suitable for next generation 3G handsets as well as WiBro and WiFi applications. The MIC2807 is currently available in volume with pricing starting at $2.50 for 1K quantity.
The output voltage of the buck regulator in the MIC2807 can be dynamically adjusted with an external DAC to maximize talk time of the cell phone. By adjusting the voltage applied to the RF power amplifier, transmit power can be made to match environmental operating conditions. When close to a base station, output power can be set low, while in weak signal areas, the phone may require increased transmit power to maintain a reliable connection. In maximum power situations, the MIC2807 has a by-pass mode which connects the RF PA directly to the battery, thereby providing maximum current to the load. This internal 75mOhm bypass switch is automatically activated when the DAC control voltage exceeds a preset level.
The IC features a 2.7V to 5.5V input voltage range with a DAC-adjustable output voltage from 0.3V up to 3.6V. In PWM mode, the MIC2807 buck regulator will supply more than 600mA of output current through its fully integrated MOSFET switches. In bypass mode, it can source in excess of 1 Amp to the load. One of the linear regulators within the device can provide up to 200mA and is suitable for powering the RF transceiver while the other can source up to 30mA. Both linear regulators have a high ripple rejection of 70db at 1kHz and a low output noise of 32uVRMS typically. The MIC2807 is fully protected against output faults and extreme operating conditions by output current limiting in PWM and Bypass modes, and on-chip thermal sensing and shut-down.
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