AD8128ACPZ-R7

Overview

The AD8128ACPZ-R7 is a high-speed differential receiver and equalizer designed to compensate for transmission losses in unshielded twisted pair (UTP) Category-5 cables. It achieves an equalized bandwidth of 120 MHz for cable lengths up to 100 meters, with ±1 dB flatness extending to 70 MHz. The device operates on a ±5 V supply with a quiescent current of 24 mA per supply rail. Key electrical characteristics include a slew rate of 2700 V/μs, an integrated output noise of 1.5 mV rms over a 1 GHz bandwidth, and a typical DC offset voltage error of 7 mV.

Feature Summary

• Compensates for frequency-dependent attenuation in CAT-5/CAT-5e cables using summed zero-pole pairs.
• Features two voltage-controlled pins for independent adjustment of broadband gain and high-frequency peaking.
• Includes a DC offset adjust pin allowing output shifting of ±2.5 V for dc-coupled system flexibility.
• Supports cascading two devices to extend equalization range up to 200 meters.

Applications

• Keyboard-video-mouse (KVM) systems
• RGB video transmission over unshielded twisted pair (UTP) cables
• Professional video projection and distribution networks
• Security video surveillance receivers

Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation to confirm package type and reel configuration. The AD8128ACPZ-R7 utilizes an 8-lead LFCSP package. Ensure that the procurement source provides valid traceability and that the component meets RoHS compliance standards as specified in the datasheet. Cross-reference the part number with the latest revision A data sheet to confirm functional equivalence.

Selection Notes

Select this component for applications requiring low-noise equalization of CAT-5 cables up to 100 meters. The device supports both differential and single-ended inputs and offers adjustable gain controls to accommodate varying cable lengths. For longer distances exceeding 100 meters, consider cascading multiple units. Ensure the design accommodates the required ±5 V power supply and provides adequate thermal dissipation through the exposed pad connection.

Part Context

The AD8128 belongs to Analog Devices' line of cable equalizers, specifically engineered for video signal integrity over UTP cabling. It serves as a standalone receiver or complements triple differential receivers like the AD8143 in multi-channel KVM architectures. The device integrates high-speed analog processing within a compact 3 mm × 3 mm footprint, facilitating dense PCB layouts for professional AV and security infrastructure.

Replacement Considerations

Publicly confirmed substitutes include the AD8123 and AD8124 from Analog Devices. The AD8123 is a triple differential receiver with similar equalization capabilities, while the AD8124 offers adjustable equalization for up to 200 meters. Verify pin compatibility and control voltage requirements when transitioning between these variants.

FAQ

How are the VGAIN and VPEAK control voltages determined?

The control voltages are linearly correlated to the cable length. VGAIN can be approximated by dividing the cable length in meters by 425, and VPEAK by dividing the length by 110. These values should be optimized based on specific cable characteristics.

Can the AD8128 handle cable lengths longer than 100 meters?

Yes, by cascading two AD8128 devices in series, the system can provide equalization for up to 200 meters of CAT-5 cable. This configuration may slightly degrade rise time, settling time, and increase integrated noise.

What is the purpose of the VOFFSET pin?

The VOFFSET pin allows for DC output offset adjustment within a range of ±2.5 V. This feature provides flexibility for DC-coupled systems by enabling the user to shift the output voltage level to match downstream input requirements.