Maxim has introduced ICs that set and control bias conditions for dual Mesfet power devices found in point-to-point communication and other microwave base stations. The MAX11014 integrates closed-loop drain-current control for class A Mesfet amplifier operation, while the MAX11015 sets the Mesfet gate voltage for class AB operation. Both devices integrate SRAM look-up tables (LUTs) that can be used to store temperature and drain-current compensation data.
The MAX11014/MAX11015 are said to be unique in their unmatched level of integration. Each device includes dual, high-side, current-sense amplifiers to monitor the Mesfet drain currents through the voltage drop across the sense resistors in the 0 to 625 mV range. External diode-connected transistors monitor the Mesfet temperatures, while an internal temperature sensor measures the local die temperature. An internal DAC sets the voltages across the current-sense resistors by controlling the gate voltages. The internal 12-bit SAR ADC digitises internal and external temperature, internal DAC voltages, current-sense amplifier voltages, and external gate voltages. Two of the 11 ADC channels are available as general-purpose analog inputs for analog system monitoring. An internal reference provides a regulated, low-noise, +2,5 V reference for the ADC, DAC, and temperature sensors while still allowing the flexibility to operate from the ADC's and DAC's individual external references.
The MAX11014's gate-drive amplifier functions as an integrator for the drain-current control loop, while the MAX11015's gate-drive amplifier functions with a gain of -2 for class AB applications. The current-limited gate-drive amplifier can be fast clamped to a programmable analog voltage independent of the digital input from the serial interface. Both the MAX11014 and MAX11015 include self-calibration modes to minimise error over time, temperature, and supply voltage.
These two bias controllers communicate over a 20 MHz SPI 4-wire serial interface or a 3,4 MHz I²C serial interface.
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