LTC6421CUDC-20#PBF

Overview

The LTC6421CUDC-20#PBF is a dual high-speed differential amplifier and ADC driver from Analog Devices, designed for processing signals from DC to 140MHz. It features a fixed gain of 20dB (10V/V) with a 1.3GHz -3dB bandwidth. The device operates on a single supply voltage ranging from 2.85V to 3.5V, consuming 40mA per amplifier. It includes adjustable output common mode voltage control between 1V and 1.6V. Key electrical specifications include a noise figure of 6.2dB, an equivalent OIP3 of 42dBm at 100MHz, and a slew rate of 4500V/µs. The component is housed in a compact 20-lead 3mm × 4mm QFN package.

Feature Summary

• Dual matched amplifiers with precise channel-to-channel gain matching of ±0.1dB and phase matching of ±0.2° at 100MHz.
• Integrated output common mode voltage control allows direct driving of ADCs without external transformers or AC-coupling capacitors.
• High linearity performance with low distortion characteristics suitable for demanding signal processing applications.
• Supports both DC and AC coupling configurations for flexible input and output interfacing.

Applications

• Differential ADC Driver
• Single Ended to Differential Conversion
• IF Sampling (Diversity) Receivers
• Broadband I/Q Amplifiers
• Satellite Communications

Procurement Notes

Verify the specific temperature grade suffix 'C' indicates operation from 0°C to 70°C, distinct from the industrial grade 'I'. Confirm the '#PBF' suffix denotes lead-free finish and tube packaging. Ensure compatibility with the 20-lead QFN footprint during PCB layout. Check current availability status as distribution may vary by region.

Selection Notes

Select this part when a fixed 20dB gain is required for broadband signal conditioning. Choose the 'C' grade version if the application environment remains within commercial temperature limits. Consider the 'I' grade variant if extended temperature range support is necessary. Evaluate power consumption constraints against the 40mA per amplifier specification.

Part Context

This component belongs to the LTC6421-20 family of dual matched differential amplifiers. It shares architectural similarities with the LTC6420-20 but offers optimized power characteristics. The device integrates feedback resistors to set the internal gain, simplifying circuit design compared to discrete solutions. It serves as a bridge between analog front-end signals and high-speed data converters.

Replacement Considerations

LTC6421IUDC-20#PBF: Industrial temperature grade (-40°C to 85°C).

FAQ

How is the output common mode voltage controlled?

The output common mode voltage is set independently via the VOCMA and VOCMB pins, allowing adjustment within a range of 1V to 1.6V.

What is the differential input impedance?

The differential input impedance is nominally 200Ω, which can be terminated to match lower source impedances like 50Ω using external components.

Can the device operate with AC-coupled inputs?

Yes, the inputs can be AC-coupled. In this configuration, the input common mode voltage is automatically biased close to the VOCM setting.