Dual RF LDMOS Bias Controllers with I²C/SPI Interface

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Offers Integration, Reduces Cost with Power Savings

Part Details
  • Integrated High-Side Drain Current-Sense PGA with Gain of 2, 10, or 25
  • ±0.5% Accuracy for Sense Voltage Between 75mV and 250mV
  • Full-Scale Sense Voltage of 100mV with Gain of 25
  • Full-Scale Sense Voltage of 250mV with Gain of 10
  • Common-Mode Range of 5V to 30V Drain Voltage for LDMOS
  • Adjustable Low Noise 0 to 5V, 0 to 10V Output Gate-Bias Voltage Ranges with ±10mA Gate Drive
  • Fast Clamp to 0V for LDMOS Protection
  • 8-Bit DAC Control of Gate-Bias Voltage
  • 10-Bit DAC Control of Gate-Bias Offset with Temperature
  • Internal Die Temperature Measurement
  • External Temperature Measurement by Diode-Connected Transistor (2N3904)
  • Internal 12-Bit ADC Measurement of Temperature, Current, and Voltages
  • Selectable I²C-/SPI-Compatible Serial Interface
    • 400kHz/1.7MHz/3.4MHz I²C-Compatible Control for Settings and Data Measurement
    • 16MHz SPI-Compatible Control for Settings and Data Measurement
  • Internal 2.5V Reference
  • Three Address Inputs to Control Eight Devices in I²C Mode
Additional Details
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The MAX1385/MAX1386 set and control bias conditions for dual RF LDMOS power devices found in cellular base stations. Each device includes a high-side current-sense amplifier with programmable gains of 2, 10, and 25 to monitor LDMOS drain current over the 20mA to 5A range. Two external diode-connected transistors monitor LDMOS temperatures while an internal temperature sensor measures the local die temperature of the MAX1385/MAX1386. A 12-bit ADC converts the programmable- gain amplifier (PGA) outputs, external/internal temperature readings, and two auxiliary inputs.

The two gate-drive channels, each consisting of 8-bit coarse and 10-bit fine DACs and a gate-drive amplifier, generate a positive gate voltage to bias the LDMOS devices. The MAX1385 includes a gate-drive amplifier with a gain of 2 and the MAX1386 gate-drive amplifier provides a gain of 4. The 8-bit coarse and 10-bit fine DACs allow up to 18 bits of resolution. The MAX1385/MAX1386 include autocalibration features to minimize error over time, temperature, and supply voltage.

The MAX1385/MAX1386 feature an I²C/SPI™-compatible serial interface. Both devices operate from a 4.75V to 5.25V analog supply (3.2mA supply current), a 2.7V to 5.25V digital supply (3.1mA supply current), and a 4.75V to 11.0V gate-drive supply (4.5mA supply current). The MAX1385/MAX1386 are available in a 48-pin thin QFN package.


  • Industrial Process Control
  • RF LDMOS Bias-Control in Cellular Base Stations

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