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Home > Products > Integrated Circuits (ICs) > Linear > Special Purpose Amplifiers

Analog Devices Inc. LTC6421IUDC-20#PBF

Name: LTC6421IUDC-20#PBF
Brand: Analog Devices Inc.
SKU: LTC6421IUDC-20#PBF
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LTC6421IUDC-20#PBF

Manufacturer:: Analog Devices Inc.

Category:: Special Purpose Amplifiers

Package:: 20-WFQFN Exposed Pad

Datasheet:: LTC6421IUDC-20#PBF.pdf

Description:: IC ADC DRIVER 20QFN

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LTC6421IUDC-20#PBF from Analog Devices (formerly Linear Technology) is a dual, matched, high-speed differential amplifier optimized as an ADC driver for 12–16-bit converters. It delivers fixed 20dB (10V/V) gain, ±0.1dB gain matching and ±0.2° phase matching at 100MHz, with 1.3GHz –3dB bandwidth and rail-to-rail output swing - enabling direct DC-coupled interface to high-resolution analog-to-digital converters in wideband receiver front-ends.

For engineers reviewing the LTC6421IUDC-20#PBF datasheet, LTC6421IUDC-20#PBF pinout, LTC6421IUDC-20#PBF application, or LTC6421IUDC-20#PBF equivalent, key selection criteria include channel-to-channel matching performance, VOCM-controlled common-mode output flexibility, low 6.2dB noise figure at 100MHz, and QFN-20 package compatibility with high-density RF/ADC layout requirements.

Technical Context

The LTC6421IUDC-20#PBF integrates two fully differential amplifiers with on-chip 100Ω/1000Ω feedback networks, delivering precise 20dB gain without external resistors. Its internal common-mode feedback loop (300MHz –3dB BW) enables fast rejection of output common-mode disturbances while the VOCM pin provides independent, high-impedance control over output common-mode voltage (1V to 1.6V).

Each channel features 200Ω differential input impedance, 25Ω differential output impedance, and unconditionally stable operation into varied loads. The device supports both AC- and DC-coupled I/O configurations and achieves –76dBc IMD3 at 100MHz with 2VP-P output, making it suitable for demanding IF sampling and I/Q signal chain applications requiring tight amplitude/phase tracking.

Key Specifications

Parameter	Value and Actual Design Meaning
Gain	Fixed 20dB (10V/V); eliminates need for external gain-setting resistors and ensures consistent signal scaling across channels.
–3dB Bandwidth	1.3GHz; supports wideband signal processing up to 140MHz baseband with flat frequency response.
Gain Matching	±0.1dB (typ) at 100MHz; enables accurate amplitude balancing in dual-path I/Q or diversity receiver architectures.
Phase Matching	±0.2° (typ) at 100MHz; preserves quadrature integrity and minimizes image rejection degradation in coherent systems.
Noise Figure	6.2dB at 100MHz (RL = 375Ω); ensures minimal SNR degradation when driving high-performance ADCs like LTC2285.
OIP3	42dBm at 100MHz; provides robust linearity for handling multi-tone signals in communications receivers.
Supply Current	40mA per amplifier (120mW); balances low power consumption with high-speed performance for thermally constrained designs.
Output Common Mode Range	1V to 1.6V, set via VOCM pin; allows direct interfacing to ADC VCM pins (e.g., LTC22xx series) without level-shifting circuitry.

Pinout & Package

Package: 20-lead 3mm × 4mm × 0.75mm plastic QFN (UDC), exposed pad connected to V–. RoHS-compliant, lead-free finish.

Pin/Terminal	Circuit Role	Design Meaning
+INA, –INA	Differential Input A	High-impedance, matched inputs for Channel A; 200Ω differential input impedance enables direct termination to 50Ω sources via shunt or balun.
+INB, –INB	Differential Input B	Independent, matched inputs for Channel B; identical electrical characteristics to Channel A for true dual-path symmetry.
+OUTA, –OUTA	Differential Output A	Rail-to-rail outputs with 25Ω differential impedance; drive ADC inputs directly or through simple LC filtering.
+OUTB, –OUTB	Differential Output B	Electrically isolated output pair; maintains >80dB channel separation at 100MHz to prevent crosstalk in dual-channel systems.
VOCMA, VOCMB	Output Common Mode Control A/B	High-impedance DC bias inputs; each sets respective channel's output common mode voltage independently (1V–1.6V range).
ENABLEA, ENABLEB	Channel Enable/Shutdown	Active-low logic inputs; disable individual channels to reduce supply current to 1–3mA per amplifier in shutdown mode.
V+ A, V+ B	Positive Supply A/B	Separate supply pins per channel; bypass individually with 0.1μF + 1000pF capacitors to suppress PSRR-induced noise.
V– (Pins 3,4,13,14,21)	Negative Supply / Exposed Pad	All five connections must be tied to same ground plane; exposed pad (Pin 21) is electrically V– and requires soldering for thermal and electrical integrity.

Key Features

Feature	Design Value
Dual-channel gain and phase matching	±0.1dB gain match and ±0.2° phase match at 100MHz enable high-fidelity I/Q signal processing without calibration overhead.
VOCM-controlled output common mode	Independent 1V–1.6V output common-mode setting per channel eliminates transformers and AC-coupling capacitors for direct ADC interfacing.
Rail-to-rail output swing	Supports ≥2VP-P differential output swing even while sourcing/sinking 20mA, maximizing dynamic range utilization of downstream ADCs.
Low-noise, high-linearity architecture	6.2dB noise figure and 42dBm OIP3 at 100MHz ensure clean signal conditioning in wideband receiver front-ends up to 140MHz.
Flexible I/O coupling	DC- or AC-coupled inputs and outputs; single-ended or differential input support simplifies integration into diverse signal chain topologies.
Low-power shutdown mode	Per-channel enable pins reduce supply current to ≤3mA per amplifier in shutdown, supporting power-gating in multi-channel systems.

Applications

Direct-Conversion Receiver I/Q Path	Dual-Channel ADC Front-End
Use Scenario: Wideband satellite or cellular receiver using quadrature demodulation with separate I and Q paths feeding parallel ADCs. IC Role / Device Role / Timing Role: Dual-channel differential amplifier providing matched gain, phase, and common-mode control to preserve I/Q orthogonality and minimize image rejection loss. Use Value: ±0.1dB/±0.2° matching and 80dB channel separation maintain >60dB image rejection without digital correction, reducing FPGA resource usage.	Use Scenario: High-speed data acquisition system using dual 14-bit ADCs (e.g., LTC2285) for simultaneous sampling of complementary signals. IC Role / Device Role / Timing Role: Precision ADC driver delivering rail-to-rail differential output swing and low 6.2dB noise figure to maximize ENOB at full sample rates. Use Value: Direct DC-coupled interface with VOCM-to-VCM connection eliminates external bias networks, saving PCB area and improving temperature stability.
IF Sampling Diversity Receiver	Broadband Test Equipment Signal Conditioning
Use Scenario: Cellular base station receiver employing antenna diversity with two parallel IF signal chains operating at 100–140MHz. IC Role / Device Role / Timing Role: Matched dual amplifier providing identical gain, bandwidth, and group delay to ensure coherent combining of diversity branches. Use Value: 1.3GHz bandwidth and <2ns 1% settling time support fast AGC response and accurate time-aligned sampling across channels.	Use Scenario: Automated test equipment requiring low-distortion, wideband signal amplification before digitization or analysis. IC Role / Device Role / Timing Role: High-linearity differential gain block delivering –76dBc IMD3 and –78dBc HD3 at 100MHz for clean spectral fidelity. Use Value: 42dBm OIP3 and 1.3GHz bandwidth allow characterization of wideband devices up to 140MHz without harmonic contamination.

Direct-Conversion Receiver I/Q Path

Dual-Channel ADC Front-End

Use Scenario: Wideband satellite or cellular receiver using quadrature demodulation with separate I and Q paths feeding parallel ADCs.

IC Role / Device Role / Timing Role: Dual-channel differential amplifier providing matched gain, phase, and common-mode control to preserve I/Q orthogonality and minimize image rejection loss.

Use Value: ±0.1dB/±0.2° matching and 80dB channel separation maintain >60dB image rejection without digital correction, reducing FPGA resource usage.

Use Scenario: High-speed data acquisition system using dual 14-bit ADCs (e.g., LTC2285) for simultaneous sampling of complementary signals.

IC Role / Device Role / Timing Role: Precision ADC driver delivering rail-to-rail differential output swing and low 6.2dB noise figure to maximize ENOB at full sample rates.

Use Value: Direct DC-coupled interface with VOCM-to-VCM connection eliminates external bias networks, saving PCB area and improving temperature stability.

IF Sampling Diversity Receiver

Broadband Test Equipment Signal Conditioning

Use Scenario: Cellular base station receiver employing antenna diversity with two parallel IF signal chains operating at 100–140MHz.

IC Role / Device Role / Timing Role: Matched dual amplifier providing identical gain, bandwidth, and group delay to ensure coherent combining of diversity branches.

Use Value: 1.3GHz bandwidth and <2ns 1% settling time support fast AGC response and accurate time-aligned sampling across channels.

Use Scenario: Automated test equipment requiring low-distortion, wideband signal amplification before digitization or analysis.

IC Role / Device Role / Timing Role: High-linearity differential gain block delivering –76dBc IMD3 and –78dBc HD3 at 100MHz for clean spectral fidelity.

Use Value: 42dBm OIP3 and 1.3GHz bandwidth allow characterization of wideband devices up to 140MHz without harmonic contamination.

Equivalent & Alternatives

The following parts are listed as comparable options for similar differential ADC driver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LTC6401IUDC-20#PBF	Same gain (20dB), but single-channel; lower supply current (22mA vs 40mA per amp); 1.1GHz bandwidth vs 1.3GHz.	Not suitable for dual-path I/Q or diversity systems requiring matched channels; better for space-constrained single-channel designs.	Select LTC6401IUDC-20#PBF only when dual-channel matching is unnecessary and power reduction is prioritized over bandwidth.
LTC6420IUDC-20#PBF	Same dual-channel architecture and pinout; higher distortion (IMD3 = –72dBc vs –76dBc); identical gain, matching, and bandwidth specs.	Suitable for less demanding linearity requirements; shares same footprint and VOCM control but trades SNR for cost.	Choose LTC6420IUDC-20#PBF if system-level SFDR budget allows 4dB margin reduction and cost sensitivity outweighs ultimate linearity.

Compared with LTC6401IUDC-20#PBF and LTC6420IUDC-20#PBF, the LTC6421IUDC-20#PBF uniquely combines dual-channel matching, highest linearity (–76dBc IMD3), and widest bandwidth (1.3GHz) in a single 3mm×4mm QFN package - making it optimal for precision I/Q and diversity receiver signal chains where channel coherence is critical.

Availability

LTC6421IUDC-20#PBF is available at Aetrix Electronics and suitable for high-speed data acquisition, wideband communications infrastructure, and precision test equipment requiring stable component supply across extended industrial temperature ranges.

Supply support for LTC6421IUDC-20#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.

The LTC6421IUDC-20#PBF belongs to Linear Technology's high-speed differential amplifier product line, designed specifically to replace transformer-based ADC driver solutions with integrated, low-power, matched dual-channel ICs for wideband receiver and instrumentation applications.

FAQ

What is the operating temperature range for the LTC6421IUDC-20#PBF?

The LTC6421IUDC-20#PBF is specified for operation from –40°C to +85°C, meeting industrial-grade reliability requirements. This extended temperature range is guaranteed by production testing and applies to all DC and AC electrical specifications listed in the datasheet, including gain matching, noise figure, and OIP3 performance.

Can the LTC6421IUDC-20#PBF drive ADCs with 50Ω differential input impedance?

Yes, the LTC6421IUDC-20#PBF can drive 50Ω differential ADC inputs using external series resistors (e.g., 12.5Ω per output) or LC matching networks. Its 25Ω differential output impedance is intentionally low to ensure stability; adding 12.5Ω series resistance yields a near-ideal 50Ω source impedance for minimal reflection and optimal power transfer to standard ADC inputs.

How does the VOCM pin function in the LTC6421IUDC-20#PBF?

The VOCM pin in the LTC6421IUDC-20#PBF is a high-impedance input that directly sets the output common-mode voltage for its associated channel between 1V and 1.6V. When connected to an ADC's VCM pin (e.g., LTC2285), it establishes precise DC bias alignment, enabling direct DC-coupled connection without transformers or AC-coupling capacitors - reducing component count and phase skew.

Is the LTC6421IUDC-20#PBF pin-compatible with other members of the LTC642x family?

Yes, the LTC6421IUDC-20#PBF shares identical 20-lead QFN (UDC) pinout and footprint with LTC6420IUDC-20#PBF and LTC6421CUDC-20#PBF. All variants use the same pin assignments for power, I/O, VOCM, and enable functions - allowing drop-in replacement within the same temperature grade and gain configuration, provided system-level linearity and noise requirements are verified.

What is the significance of the ±0.1dB gain matching specification for the LTC6421IUDC-20#PBF?

The ±0.1dB gain matching specification for the LTC6421IUDC-20#PBF ensures amplitude consistency between its two amplifier channels across frequency and temperature. In I/Q receiver systems, this tight matching prevents image signal leakage and maintains >60dB image rejection without requiring complex digital calibration algorithms - directly improving system-level dynamic range and measurement accuracy.

LTC6421IUDC-20#PBF Specifications

Product attributes: Attribute value

Manufacturer:: Analog Devices Inc.

Series:: -

Package/Case:: 20-WFQFN Exposed Pad

Packaging:: Tube

Product Status:: Last Time Buy

Type:: ADC Driver

Applications:: Data Acquisition

Mounting Type:: Surface Mount

Grade:: -

Qualification:: -

Supplier Device Package:: 20-QFN (3x4)

LTC6421IUDC-20#PBF FAQ

1.How can I place an order for LTC6421IUDC-20#PBF through Aetrix?

Please submit a Request for Quotation (RFQ) for LTC6421IUDC-20#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for LTC6421IUDC-20#PBF reliable?

The price and inventory of LTC6421IUDC-20#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC6421IUDC-20#PBF is usually 5 days.

3.What payment methods are accepted for LTC6421IUDC-20#PBF?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC6421IUDC-20#PBF transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LTC6421IUDC-20#PBF?

LTC6421IUDC-20#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LTC6421IUDC-20#PBF order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for LTC6421IUDC-20#PBF?

For technical support, including LTC6421IUDC-20#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC6421IUDC-20#PBF requirements.

6.How does Aetrix verify that LTC6421IUDC-20#PBF is sourced from the original manufacturer or authorized distributors?

All LTC6421IUDC-20#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LTC6421IUDC-20#PBF meets industry standards.

7.What is the process for return or replacement of LTC6421IUDC-20#PBF?

All LTC6421IUDC-20#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC6421IUDC-20#PBF, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The LTC6421IUDC-20#PBF part is unused and in its original packaging.

Return procedure for LTC6421IUDC-20#PBF:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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