AS1339 Step-Down Converter IC

Description

The AS1339 is a high-frequency step-down converter optimized for dynamically powering the power amplifier (PA) in WCDMA or NCDMA handsets. The device uses a 110mΩ typical bypass FET to power the PA directly from the battery during high-power transmission. The IC integrates two 10mA low-noise, low-dropout regulators (LDOs) for PA biasing.

With a switching frequency of 2MHz, the device allows optimization for smallest solution size or highest efficiency. The AS1339 supports fast switching using small ceramic 10μF input and 4.7µF output capacitors to maintain low ripple voltage.

The AS1339 uses an analog input driven by an external DAC to control the output voltage linearly for continuous PA power adjustment. The gain from REFIN to OUT is 2.5V/V. At high-duty cycle, the device automatically switches to a bypass mode, connecting the input to the output through a low-impedance MOSFET. The LDOs are designed for low-noise operation, wherein each LDO in the device is individually enabled through its own logic control interface. The device is available in a 16-pin WLP (2x2mm) package.

Key Features

• Input Voltage Range: 2.7V to 5.5V
• Dynamic Output Voltage Control (0.8V to 3.75V)
• Fixed Switching Frequency: 2MHz
• PA Step-Down Converter
• Low Dropout Voltage
• Low Output-Voltage Ripple
• 30µs Settling Time for 0.8V to 3.4V Output Voltage Range
• 650mA Output Drive Capability
• Two 10mA Low-Noise LDOs
• Low Shutdown Current
• Thermal Shutdown
• 16-pin WLP (2x2mm) package

Applications

The AS1339 is ideal for WCDMA/NCDMA cellular handsets, Wireless PDAs, and Smartphones.

Block diagram for AS1339 Step-Down Converter IC