MAX1958

` Buck Converter Dynamically Adjustable Output from 0.75V to 3.4V (MAX1958) Dynamically Adjustable Output from 1V to 3.6V (MAX1959) 1MHz Fixed-Frequency PWM 800mA Guaranteed Output Current 130mV IC Dropout at 600mA Load 16% to 100% Duty-Cycle Operation Low Quiescent Current 190A (typ) in Skip Mode (MAX1958) 3mA (typ) in PWM Mode 0.01A (typ) in Shutdown Mode No External Schottky Diode Required
` Operational Amplifier Active Output Discharge in Shutdown Mode 800kHz Gain-Bandwidth Product 120dB Open-Loop Voltage Gain (R_L = 100k) 5mA Rail-to-Rail Output
` Temperature Sensor -40 to +125 Rated Temperature Range Accurate Sensor, -11.64mV/ Slope

The MAX1958/MAX1959 evaluation (EV) kit demonstrates an application circuit ideal for use with hetero-junction bipolar transistor power amplifiers (HBT PA). The MAX1958/MAX1959 application circuit features an 800mA DC-to-DC buck converter, an operational amplifier, and a high-accuracy temperature sensor.

The high-efficiency, dynamically adjustable, pulse-width modulated (PWM), DC-to-DC buck converter is optimized to provide power to the HBT PA in N-CDMA and W-CDMA cellular phones. The 1MHz PWM switching frequency allows the use of small external components, while skip mode reduces quiescent current to 190A with light loads. The buck regulator is dynamically controlled to provide any fixed output voltage in the 0.75V to 3.4V (MAX1958) and 1V to 3.6V (MAX1959) ranges. The DC-to-DC converter utilizes a low on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency and minimize external component count.

The built-in operational amplifier is used to provide full bias control for the PA to maximize efficiency. The amplifier has Rail-to-Rail® input/output capability, 800kHz gain-bandwidth product, and 120dB open-loop voltage gain. An added feature of the amplifier is an active output discharge in shutdown mode.The precision temperature sensor measures temperatures between -40 and +125.This fully tested EV kit comes with the MAX1958 IC installed. The MAX1959 has an identical pinout arrangement and can be evaluated on this board. To evaluate the MAX1959, request a free sample of the MAX1959 when ordering this evaluation kit.