説明

HMC981LP3E is an active bias controller that automatically adjusts the gate voltage of an external amplifier to achieve constant bias current. It can be used to bias any enhancement and depletion type amplifiers operating in Class-A regime with Drain voltages from 4V to 12V and drain currents up to 200mA, offering a complete biasing solution.

HMC981LP3E achieves excellent bias stability over supply, temperature and process variations, and eliminates the required calibration procedures usually employed to prevent RF performance degradation due to such variations.

The HMC981LP3E is housed in an RoHS compliant 3×3 mm QFN leadless package with an exposed backside pad to improve thermal characteristics.

 

特徴

Automatic Gate voltage adjustment (No Calibration required)

Supply Voltage: 4V to 12V

Digital Voltage: 3.3V to 5V

Controls both Enhancement and Depletion type devices

Adjustable Drain Current up to 200mA

Sink/Source Gate Current Capability

Optional Internal negative voltage generation that can be disabled to use external negative rail

Fast Enable/Disable

Trigger-out Output for Daisy Chain Power-Up and Power-Down Sequencing

16 Lead 3×3 mm SMT Package: 9 mm²

 

代表的なアプリケーション

マイクロ波無線とVSAT

Military & Space

試験計装

Fiber Optic Modulator Driver Biasing

CATV Laser Driver Biasing

Cellular Base Station

Wireless Infrastructure Equipment

 

詳細

The HMC981LP3E is a fully-integrated Active Bias Controller (ABC) that automatically adjusts the gate voltage of amplifiers operating in the Class-A regime. With an internal feedback the automatic gate voltage control achieves constant quiescent bias through the amplifier under bias, independent of temperature and amplifier threshold variations. The quiescent current is adjusted with a resistor connected externally. The HMC981LP3E employs an integrated control circuitry to achieve safe power-up and power-down sequencing of the targeted amplifier. The HMC981LP3E can provide auto-bias solution virtually any amplifier in the market (both enhancement and depletion type) with a quiescent current of up to 200 mA and a supply voltage of up to 12V.

The HMC981LP3E has an integrated negative voltage generator to synthesize negative voltages required to drive depletion mode amplifiers. If an external negative supply is already available or an enhancement mode device is targeted, the negative voltage generator can be disabled.

The HMC981LP3E achieves excellent bias stability over supply and temperature variations with low supply voltage down to 4V. The gate control can both sink and source current (±0.8 mA) to achieve constant bias current over input power variations applied to the amplifier. The HMC981LP3E also generates a second gate voltage (VG2). VG2 can be adjusted through a resistor divider connected to VDD for amplifiers which require second gate voltage.

The HMC981LP3E ensures the protection of the external amplifier during turn on/off by adjusting the sequence of VDRAIN, VGATE and VG2 outputs. HMC981LP3E controls the bias current of the amplifier under bias with the gate control driver. The current passing through the amplifier is continuously sampled and is used to control the VGATE voltage connected to the gate of the amplifier.

The HMC981LP3E employs a SW pin to control RDS_ON resistance of the internal switch between VDD and VDRAIN. Refer to the section under the “Supply and Drain Voltage” section for details.

The HMC981LP3E has a built-in short circuit protection feature to protect both itself and the amplifier under bias against short circuit conditions at the VDRAIN output.

Digital Power Supply (VDIG)

The HMC981LP3E requires an external low voltage bias rail (3.3V to 5.0V). VDIG powers the internal logic circuitry. VDIG draws an average of 3 mA from a 3.3V. VDIG can accept voltages up to 5.0V.

Supply and Drain Voltage (VDD and VDRAIN)

The VDD supply to the HMC981LP3E is directly connected to the VDRAIN output through an internal MOSFET switch. This internal MOSFET is controlled through power-up sequencing which ensures that no voltage is applied to drain of the external amplifier until the gate voltage is pulled down to VNEG(ensuring external amplifier is pinched-off). The VDRAIN output of the HMC981LP3E should be connected to the drain (collector) of the amplifier under bias for the active bias control feedback and power-up/down sequencing to work.