Dual RF LDMOS Bias Controller with Nonvolatile Memory

The MAX11008 controller biases RF LDMOS power devices found in cellular base stations and other wireless infrastructure equipment. Each controller includes a high-side current-sense amplifier with programmable gains of 2, 10, and 25 to monitor the LDMOS drain current over a range of 20mA to 5A. The MAX11008 supports up to two external diode-connected transistors to monitor the LDMOS temperatures while an internal temperature sensor measures the local die temperature. A 12-bit successive-approximation register (SAR) analog-to-digital converter (ADC) converts the analog signals from the programmable-gain amplifiers (PGAs), external temperature sensors, internal temperature measurement, and two additional auxiliary inputs. The MAX11008 automatically adjusts the LDMOS bias voltages by applying temperature, AIN, and/or drain current samples to data stored in lookup tables (LUTs).

The MAX11008 includes two gate-drive channels, each consisting of a 12-bit DAC to generate the positive gate voltage for biasing the LDMOS devices. Each gate-drive output supplies up to ±2mA of gate current. The gate-drive amplifier is current-limited to ±25mA and features a fast clamp to AGND.

The MAX11008 contains 4Kb of on-chip, nonvolatile EEPROM organized as 256 bits x 16 bits to store LUTs and register information. The device operates from either a 4-wire 16MHz SPI™-/MICROWIRE™-compatible or an I²C-compatible serial interface.

The MAX11008 operates from a +4.75V to +5.25V analog supply with a typical supply current of 2mA, and a +2.7V to +5.25V digital supply with a typical supply of 3mA. The device is packaged in a 48-pin, 7mm x 7mm, thin QFN package and operates over the extended (-40°C to +85°C) temperature range.

Applications

* Cellular Base Stations * Feed-Forward Power Amps * Industrial Process Control * Microwave Radio Links * Transmitters

* On-Chip 4Kb EEPROM for Storing LDMOS Bias Characteristics

* Integrated High-Side Current-Sense PGA with Gain of 2, 10, or 25

* ±0.75% Accuracy for Sense Voltage Between +75mV and +1250mV

* Full-Scale Sense Voltage

* +100mV with a Gain of 25

* +250mV with a Gain of 10

* +1250mV with a Gain of 2

* Common-Mode Range, LDMOS Drain Voltage: +5V to +32V

* Adjustable Low-Noise 0 to AVDD Output Gate Bias Voltage Range

* Fast Clamp to AGND for LDMOS Protection

* 12-Bit DAC Control of Gate with Temperature

* Internal Die Temperature Measurement

* 2-Channel External Temperature Measurement through Remote Diodes

* Internal 12-Bit ADC Measurement for Temperature, Current, and Voltage Monitoring

* User-Selectable Serial Interface

* 400kHz/1.7MHz/3.4MHz I²C-Compatible Interface

* 16MHz SPI-/MICROWIRE-Compatible Interface