Dual RF LDMOS Bias Controllers with I²C/SPI Interface

Offers Integration, Reduces Cost with Power Savings

Please check latest availability status for a specific part variant.


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.
MAX1385, MAX1386: Typical Operating Circuit (I²C Mode) MAX1385, MAX1386: Typical Operating Circuit (I²C Mode) Enlarge+

Key Features

  • 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


  • Industrial Process Control
  • RF LDMOS Bias-Control in Cellular Base Stations
Part NumberGate Drive Range
VBIAS ClampChannelsHigh-Side Current Sense GainLoop ControlInterfaceADCsDACsReferenceTemp. SensorAVDD
Gate Supply
MAX1385 0 to 5Yes22 @ 30VExternal Micro
8-bit Coarse
10-bit Fine
Internal to 11
See All Bias Controllers (2)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Technical Documents

Tutorial 5100 General Layout Guidelines for RF and Mixed-Signal PCBs
App Note 4065 Implementing a MAX1385-Based Control Loop in C/C++

Quality and Environmental Data

Request Reliability Report for: MAX1385 
Lead-Free Package Tin (Sn) Whisker Reports
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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