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Analog Devices Inc. LTC6421CUDC-20#PBF
- Part No.:
- LTC6421CUDC-20#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Special Purpose Amplifiers
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC6421CUDC-20#PBF.pdf
- Description:
- IC ADC DRIVER 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,757
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Product details
Overview
LTC6421CUDC-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, 1.3GHz –3dB bandwidth, ±0.1dB gain matching and ±0.2° phase matching at 100MHz, with rail-to-rail output swing and adjustable 1V–1.6V output common-mode voltage - enabling direct DC-coupled interface to precision ADCs in communications and instrumentation systems.
For engineers reviewing the LTC6421CUDC-20#PBF datasheet, LTC6421CUDC-20#PBF pinout, LTC6421CUDC-20#PBF application, or LTC6421CUDC-20#PBF equivalent, key selection criteria include channel matching performance at RF frequencies, VOCM-controlled common-mode flexibility, low 6.2dB noise figure, and QFN-20 package compatibility with high-density mixed-signal PCB layouts.
Technical Context
The LTC6421CUDC-20#PBF integrates two fully independent differential amplifiers, each with internal 100Ω/1000Ω feedback networks setting fixed 20dB gain and 200Ω differential input impedance. Its architecture features separate VOCM pins per channel, enabling independent output common-mode biasing without transformer coupling.
Each channel includes dedicated ENABLE control, isolated power supply pins (V+A/V+B, V−), and 12.5Ω series output resistors for stability across varying loads. The device operates from a single 2.85V–3.5V supply, drawing 40mA per amplifier, and maintains <±0.25dB gain match and >80dB channel separation up to 100MHz.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Gain | 20dB (10V/V) - fixed, eliminates external gain-setting components and ensures consistent signal scaling into ADC inputs. |
| –3dB Bandwidth | 1.3GHz - supports wideband IF sampling up to 140MHz baseband with flat frequency response and minimal group delay variation. |
| Gain Matching | ±0.1dB (typ) - enables precise amplitude balance in I/Q receiver paths and dual-channel data acquisition systems. |
| Phase Matching | ±0.2° at 100MHz - preserves signal integrity in coherent beamforming, diversity receivers, and time-interleaved ADC architectures. |
| Noise Figure | 6.2dB - minimizes system noise contribution when driving high-resolution ADCs with 70+ dB SNR requirements. |
| OIP3 | 42dBm at 100MHz - provides robust linearity for wide dynamic range applications such as satellite comms and spectrum analyzers. |
| Supply Current | 40mA per amplifier - balances performance and power efficiency versus discrete transformer-based solutions. |
| Output Common-Mode Range | 1V to 1.6V - matches typical ADC reference voltages (e.g., LTC2285 VCM = 1.5V), eliminating level-shifting circuitry. |
Pinout & Package
Package: 20-lead 3mm × 4mm × 0.75mm plastic QFN (UDC) with exposed thermal pad connected to V−. RoHS-compliant, lead-free finish (#PBF).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| +INA, –INA | Differential Input A | High-impedance, matched 200Ω differential input pair for Channel A; accepts DC- or AC-coupled signals. |
| +INB, –INB | Differential Input B | Independent differential input pair for Channel B; identical electrical characteristics to Channel A for matched operation. |
| +OUTA, –OUTA | Differential Output A | Low-impedance (25Ω typ) differential outputs with rail-to-rail swing; VOCMA sets common-mode level. |
| +OUTB, –OUTB | Differential Output B | Independent differential outputs for Channel B; VOCMB allows separate common-mode biasing from Channel A. |
| VOCMA, VOCMB | Output Common-Mode Control A/B | High-impedance inputs that directly set respective output common-mode voltage between 1V and 1.6V. |
| ENABLEA, ENABLEB | Channel Enable/Shutdown Control | Active-low logic inputs; disable corresponding amplifier to reduce supply current to ≤3mA per channel. |
| V+A, V+B | Positive Supply A/B | Separate supply pins per channel improve PSRR and reduce crosstalk; bypass individually with 0.1μF + 1000pF. |
| V− (Pins 3,4,13,14,21) | Negative Supply / Ground Reference | All five V− connections-including exposed pad-must be tied to same ground plane for thermal and noise performance. |
Key Features
| Feature | Design Value |
|---|---|
| Dual matched amplifiers | ±0.1dB gain match and ±0.2° phase match at 100MHz enable coherent multi-channel signal processing without calibration. |
| Adjustable output common-mode voltage | VOCM pins allow direct interfacing to ADCs with varying VCM requirements (e.g., 1.25V, 1.5V) without external resistive dividers. |
| Rail-to-rail output swing | Delivers ≥5.6VP-P differential output at VOCM = 1.5V, maximizing ADC full-scale utilization and dynamic range. |
| DC- or AC-coupled operation | Supports both coupling schemes on inputs and outputs - simplifies design of baseband, IF, and RF front-ends. |
| Low-noise, high-linearity architecture | 1nV/√Hz input-referred noise and 42dBm OIP3 ensure clean signal conditioning for 14–16-bit ADCs in demanding applications. |
| Compact thermally enhanced package | 3mm × 4mm QFN with exposed V− pad achieves θJA = 43°C/W, supporting reliable operation at 120mW per channel. |
Applications
| Direct-Conversion Receiver I/Q Path | Satellite Communications Front-End |
|---|---|
Use Scenario: Dual-channel baseband I/Q signal conditioning prior to digitization in SDR transceivers. IC Role / Device Role / Timing Role: Simultaneous, matched amplification of in-phase and quadrature analog signals with identical gain, phase, and noise characteristics. Use Value: Maintains orthogonality and amplitude balance critical for EVM <1% in QAM-256 modulation schemes up to 140MHz bandwidth. |
Use Scenario: Conditioning L-band or C-band IF signals before digitization in phased-array satellite terminals. IC Role / Device Role / Timing Role: High-linearity, low-noise amplification of 70–140MHz IF outputs from downconverters feeding dual 14-bit ADCs. Use Value: 42dBm OIP3 and 6.2dB NF preserve signal fidelity across wide instantaneous bandwidths required for multi-carrier TDMA/FDMA waveforms. |
| High-Speed Data Acquisition System | Test & Measurement Instrumentation |
Use Scenario: Driving dual-channel, time-interleaved 16-bit ADCs in oscilloscopes or spectrum analyzers. IC Role / Device Role / Timing Role: Precision differential signal buffering with sub-picosecond timing skew and matched settling behavior. Use Value: ±0.2° phase match and 2ns 1% settling time ensure accurate time alignment between interleaved ADC channels. |
Use Scenario: Signal conditioning stage in automated test equipment (ATE) for RF component characterization. IC Role / Device Role / Timing Role: Low-distortion amplification of stimulus signals and sensitive reception of DUT responses in vector network analyzers. Use Value: –76dBc IMD3 and –78dBc HD3 support accurate harmonic and intermodulation measurements at fundamental frequencies up to 100MHz. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar differential ADC driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC6401CUDC-20#PBF | Same 20dB gain and 200Ω ZIN, but lower 400MHz –3dB bandwidth and higher 10.5dB noise figure. | Better suited for sub-200MHz IF stages where ultra-low power (22mA/ch) outweighs bandwidth needs. | Select when power budget is tighter and bandwidth demand is ≤250MHz; not suitable for 1.3GHz small-signal BW requirement. |
| LTC6404IUDC-2#PBF | 2V/V (6dB) gain, 900MHz bandwidth, 1.5nV/√Hz noise, but no VOCM control or channel matching specs. | Designed for unity/gain-of-two precision AC-coupled applications; lacks matched dual-channel architecture. | Choose for single-ended-to-differential conversion or non-matched, ultra-low-noise gain blocks - not for matched I/Q or VOCM-dependent ADC interfaces. |
Compared with LTC6401CUDC-20#PBF and LTC6404IUDC-2#PBF, the LTC6421CUDC-20#PBF uniquely combines 1.3GHz bandwidth, ±0.1dB matching, and VOCM-adjustable outputs - making it the only option among the three qualified for wideband, matched dual-channel ADC driving with DC-coupled flexibility.
Availability
LTC6421CUDC-20#PBF is available at Aetrix Electronics and suitable for high-speed data acquisition, satellite communications front-ends, and direct-conversion receiver designs requiring stable component supply, matched dual-channel performance, and DC-coupled ADC interface capability.
Supply support for LTC6421CUDC-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 ICs for precision, power, and RF applications.
The LTC6421CUDC-20#PBF belongs to Linear's high-speed differential amplifier product line, engineered specifically for low-noise, low-distortion ADC driving in communications infrastructure, test equipment, and high-fidelity data acquisition systems.
FAQ
What is the operating temperature range for the LTC6421CUDC-20#PBF?
The LTC6421CUDC-20#PBF is specified for operation from 0°C to 70°C (commercial grade). While characterized over –40°C to 85°C, only the I-grade variant (LTC6421IUDC-20#PBF) is guaranteed across the full industrial range. For designs targeting extended ambient conditions, the I-grade part must be selected to ensure parametric compliance.
Can the LTC6421CUDC-20#PBF drive ADCs without external transformers or AC-coupling capacitors?
Yes - the LTC6421CUDC-20#PBF supports direct DC-coupled connection to ADCs via its VOCM pins, which set output common-mode voltage from 1V to 1.6V. This eliminates transformers and coupling capacitors in applications like baseband digitization, reducing board area, cost, and phase distortion while maintaining DC accuracy.
How does the ENABLE pin function on the LTC6421CUDC-20#PBF?
ENABLEA and ENABLEB are active-low, per-channel shutdown controls. When pulled low (<0.8V), the corresponding amplifier operates normally; when pulled high (>2.4V), it enters low-power shutdown mode with output high-impedance and supply current reduced to ≤3mA per channel - enabling dynamic power management in multi-channel systems.
What is the significance of the exposed thermal pad on the LTC6421CUDC-20#PBF QFN package?
The exposed pad (Pin 21) of the LTC6421CUDC-20#PBF is electrically and thermally connected to V−. It must be soldered to a PCB copper pour tied to the system ground plane to achieve θJA = 43°C/W and ensure stable thermal performance under continuous 120mW per channel operation.
Does the LTC6421CUDC-20#PBF require external gain-setting resistors?
No - the LTC6421CUDC-20#PBF has internally fixed 20dB (10V/V) gain established by precision on-chip 100Ω/1000Ω feedback resistors. This eliminates external gain components, reduces layout sensitivity, and guarantees consistent gain matching between channels without trimming or calibration.
LTC6421CUDC-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)
LTC6421CUDC-20#PBF FAQ
1.How can I place an order for LTC6421CUDC-20#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC6421CUDC-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 LTC6421CUDC-20#PBF reliable?
The price and inventory of LTC6421CUDC-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 LTC6421CUDC-20#PBF is usually 5 days.
3.What payment methods are accepted for LTC6421CUDC-20#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC6421CUDC-20#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC6421CUDC-20#PBF?
LTC6421CUDC-20#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC6421CUDC-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 LTC6421CUDC-20#PBF?
For technical support, including LTC6421CUDC-20#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC6421CUDC-20#PBF requirements.
6.How does Aetrix verify that LTC6421CUDC-20#PBF is sourced from the original manufacturer or authorized distributors?
All LTC6421CUDC-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 LTC6421CUDC-20#PBF meets industry standards.
7.What is the process for return or replacement of LTC6421CUDC-20#PBF?
All LTC6421CUDC-20#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC6421CUDC-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 LTC6421CUDC-20#PBF part is unused and in its original packaging.
Return procedure for LTC6421CUDC-20#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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