AD8323ARU

Overview

The AD8323ARU is a digitally controlled variable gain amplifier optimized for coaxial line driving applications. It operates from a single 5 V supply and accepts differential or single-ended inputs. The device features an 8-bit serial interface controlling gain over a 53.5 dB range with 0.7526 dB/LSB steps. It maintains a constant 75 Ω output impedance during power-up and power-down conditions, eliminating external termination needs. Key performance metrics include a 100 MHz upper bandwidth, –56 dBc SFDR at 21 MHz, and low quiescent current in sleep mode.

Feature Summary

• Maintains constant 75 Ω output impedance during power-up and power-down states
• Digitally programmable gain via SPI-compatible serial interface
• Integrated sleep mode for significant power reduction
• Optimized for DOCSIS upstream transmission standards

Applications

• Gain-programmable line drivers for cable modems
• HFC high-speed data modem upstream amplifiers
• Interactive set-top boxes requiring precise output control
• PC plug-in cable modems
• General-purpose digitally controlled variable gain blocks

Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation to confirm package type and temperature range. Ensure compatibility with required logic levels for the serial interface. Confirm that the application environment supports the specified operating temperature range and supply voltage constraints. Cross-reference pin configurations with design schematics to ensure correct integration.

Selection Notes

Select this component for applications requiring fine-step gain adjustment in coaxial line driving scenarios. The device is suitable where maintaining system impedance during state transitions is critical. Consider the SPI interface requirements and available digital control lines. Evaluate thermal management needs based on the TSSOP package and expected power dissipation under maximum load conditions.

Part Context

The AD8323 belongs to Analog Devices' family of CATV line drivers designed for DOCSIS compliance. It integrates a low-noise preamplifier, a vernier attenuation stage, and a high-power output amplifier. This architecture allows for precise control of upstream signal levels in hybrid fiber-coaxial networks while minimizing distortion and noise contributions.

Replacement Considerations

Publicly confirmed substitutes include the AD8322 for coarse step control and the AD8325 for fine step control with extended range. Verify functional equivalence regarding gain resolution, output impedance stability, and interface compatibility before substitution.

FAQ

How does the AD8323 maintain impedance during power-down?

The device utilizes an internal reverse amplifier configuration when the PD pin is asserted low. This maintains a differential output impedance of 75 Ω without requiring external termination resistors, preventing signal reflections in the cable network.

What is the gain resolution of the AD8323?

The gain is programmable in steps of 0.7526 dB per least significant bit (LSB) using an 8-bit serial word. The total gain range spans approximately 53.5 dB, allowing for precise output power adjustment.

Can the AD8323 operate with single-ended inputs?

Yes, the AD8323 accepts single-ended inputs. For optimal performance with a 75 Ω source, specific termination resistors should be used as detailed in the application circuit guidelines to match the input impedance characteristics.