AD8325ARU

Overview

The AD8325 is a digitally controlled variable gain amplifier optimized for coaxial line driving in DOCSIS upstream applications. It operates from a single 5 V supply with a gain range of 59.45 dB, adjustable in 0.7526 dB steps via an 8-bit serial interface. The device maintains a constant 75 Ω differential output impedance across all gain settings and transmit modes. Key electrical parameters include a maximum gain of 30.0 dB, minimum gain of -29.45 dB, and a quiescent current of 133 mA in transmit enable mode. It supports SPI interfaces and features low distortion performance.

Feature Summary

• Digitally programmable gain control over a 59.45 dB range with fine step resolution
• Maintains constant 75 Ω differential output impedance during both transmit enable and disable states
• Integrated sleep mode significantly reduces quiescent current consumption
• Supports standard SPI serial interface for gain programming

Applications

• DOCSIS high-speed data modems
• Interactive cable set-top boxes
• PC plug-in cable modems
• Gain-programmable line drivers

Procurement Notes

Verify the specific ordering suffix (e.g., ARU vs ARUZ) to confirm lead-free compliance status as indicated in the manufacturer's ordering guide. Ensure compatibility with the required 28-lead TSSOP package form factor. Confirm that the selected variant meets the industrial temperature range specifications of -40°C to +85°C for your intended deployment environment.

Selection Notes

Select this component for applications requiring precise digital attenuation control in CATV upstream paths. The fixed 75 Ω output simplifies board layout by eliminating external matching networks. Consider the power consumption differences between transmit enable, transmit disable, and sleep modes when designing thermal management solutions for dense packaging environments.

Part Context

The AD8325 belongs to Analog Devices' family of special purpose amplifiers designed for cable television infrastructure. It serves as a key upstream power amplifier solution, replacing discrete designs with a monolithic integrated circuit. The device integrates a preamplifier, vernier attenuator, and output stage to provide complete signal conditioning for coaxial transmission lines.

Replacement Considerations

Public documentation indicates that the MA/COM ETC-1-IT-15 transformer can substitute for the specified TOKO 617DB-A0070 transformer in evaluation circuits. No direct pin-compatible functional replacements for the AD8325 amplifier IC itself are confirmed in the provided source material.