LTC2321IUFD-14 - 14-Bit+Sign Dual 2Msps SAR ADC | ADI
MPN: LTC2321IUFD-14 ⚠ Last Time Buy| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $18.5 | $18.50 |
| 10 | $16.2 | $162.00 |
| 100 | $13.85 | $1,385.00 |
| 500 | $11.95 | $5,975.00 |
| 1,000 | $10.4 | $10,400.00 |
LTC2321IUFD-14 Overview
An SAR ADC is a successive-approximation converter that uses a binary-search algorithm against an internal DAC to digitize an input voltage in N conversion cycles for an N-bit code. SAR ADCs sit in the data-converter hierarchy below pipelined and delta-sigma ADCs but offer deterministic latency, low latency per conversion, and low power consumption - well suited for multiplexed multi-channel systems where each channel must be sampled at known, fixed time intervals.
Key features include ±1LSB INL (max), 73dB SNR at 1Msps, an internal 20ppm/°C reference, and a serial SPI/LVDS digital interface with echo clock. The differential inputs provide wide common-mode rejection, making the device robust in noisy industrial environments where ground bounce is present. The 28-QFN (4x5) exposed pad reduces thermal resistance to about 28°C/W, allowing sustained 2Msps operation without external heatsinking.
Internally, the LTC2321-14 uses two matched sample-and-hold amplifiers feeding independent SAR cores that share a single bandgap reference. Digital I/O supports both standard SPI and low-voltage differential signaling (LVDS) for noise-immune clock and data lines when paired with an FPGA. Internal dithering techniques flatten the noise floor and improve spurious-free dynamic range.
Typical applications include multichannel data acquisition systems, motor control current sensing, biomedical instrumentation, and industrial process control. The wide 8VP-P input range lets the LTC2321IUFD-14 directly digitize +/-10V-referred signals after a simple resistor-divider scaling stage, eliminating an instrumentation-front-end in many designs.
When designing with this ADC, keep analog input traces short and matched, decouple VDD with a 10µF ceramic + 1µF X7R pair, and tie the exposed pad to a clean analog ground plane. Note that the LTC2321IUFD-14 is graded for the -40°C to +85°C industrial range; choose LTC2321HUFD-14 for the -40°C to +125°C automotive grade.
This page synthesizes distributor pricing, drop-in and pin-compatible alternatives, and practical design guidance beyond what the manufacturer datasheet alone provides - useful when the LTC2321IUFD-14 is approaching obsolescence and you need a sourcing or replacement plan.
Drop-in alternatives for LTC2321IUFD-14 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LTC2321IUFD-14 (same form factor and footprint) — differing in Differential Input Range, Digital Interface, Input Type, Number of Channels, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LTC2321CUFD-14
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2321HUFD-14
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2320CUFD-16
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LTC2322CUFD-12
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LTC2321IUFD-14 Maximum Ratings & Electrical Characteristics
| Resolution | 14-bit + sign |
| Number of Channels | 2 (simultaneous sampling) |
| Architecture | SAR (Successive Approximation Register) |
| Sample Rate (per channel) | 2 Msps |
| Differential Input Range | 8 VP-P |
| Supply Voltage | 3.3 V or 5 V (single supply) |
| INL (max) | ±1 LSB |
| SNR | 73 dB at 1 Msps |
| Reference | Internal, 20 ppm/°C |
| Digital Interface | SPI / LVDS with echo clock |
| Input Type | Differential, wide common-mode range |
| Package | 28-pin QFN (4x5 mm) with exposed pad |
| Mounting Type | Surface Mount |
| Operating Temperature | -40 °C to +85 °C (industrial) |
| RoHS Status | Compliant (PBF suffix) |
| Lead-Free / Halogen-Free | Yes (PBF suffix denotes lead-free) |
LTC2321IUFD-14 Pin Configuration
| Pin 1 | GND — Analog ground |
| Pin 2 | AIN1+ — Channel 1 positive differential input |
| Pin 3 | AIN1- — Channel 1 negative differential input |
| Pin 4 | GND — Analog ground |
| Pin 5 | REF — Reference decoupling pin (internal reference bypass) |
| Pin 6 | GND — Analog ground |
| Pin 7 | AIN2+ — Channel 2 positive differential input |
| Pin 8 | AIN2- — Channel 2 negative differential input |
| Pin 9 | GND — Analog ground |
| Pin 10 | VDD — Analog supply voltage (3.3V or 5V) |
| Pin 11 | OVDD — Digital I/O supply voltage |
| Pin 12 | GND — Digital ground |
| Pin 13 | SCK — Serial clock input (SPI) |
| Pin 14 | SDO — Serial data output (SPI) |
| Pin 15 | SDI — Serial data input (SPI configuration) |
| Pin 16 | CNV — Conversion start input |
| Pin 17 | BUSY — Conversion-in-progress indicator (active high) |
| Pin 18 | LVDS — LVDS/SPI mode select |
| Pin 19 | RDLK — Read clock echo (LVDS mode) |
| Pin 20 | RDLKOUT — Read clock output (LVDS mode) |
| Pin 21 | OR+,OM- — LVDS output pair (out of range) |
| Pin 22 | DNC — Do not connect |
| Pin 23 | DNC — Do not connect |
| Pin 24 | DNC — Do not connect |
| Pin 25 | DNC — Do not connect |
| Pin 26 | DNC — Do not connect |
| Pin 27 | DNC — Do not connect |
| Pin 28 | GND — Digital ground |
Typical Applications
LTC2321IUFD-14 is suitable for 6 applications: Multichannel Data Acquisition Systems, Motor Control Current Sensing, Biomedical Instrumentation and Patient Monitoring, Industrial Process Control and PLCs, Automatic Test Equipment (ATE) and Instrumentation, Power Quality and Energy Metering.
Multichannel Data Acquisition Systems
The LTC2321IUFD-14's dual simultaneously-sampling 14-bit + sign channels at 2 Msps make it an excellent ADC for compact, multi-channel DAQ front-ends where board space and per-channel cost dominate. Each channel's 73 dB SNR at 1 Msps and ±1 LSB INL preserve the integrity of multiplexed transducer signals from strain gauges, thermocouples, and load cells. The 8VP-P differential input range lets designers scale +/-10V-referred sensor outputs directly into the ADC without an intermediate instrumentation amplifier, reducing BOM cost and noise. For multi-axis vibration test equipment, the simultaneous-sampling capability removes inter-channel skew that would otherwise corrupt FFT-derived phase relationships.
Recommended
Motor Control Current Sensing
Three-phase motor drives require synchronized current sensing on at least two phases (often three) for field-oriented control loops. The LTC2321IUFD-14's two simultaneous 2 Msps SAR conversions per chip enable dual-shunt current measurement with deterministic conversion latency of around 440 ns per cycle. The 8VP-P differential input range accommodates typical +/-5V sense-amplifier outputs directly, while the wide input common-mode range tolerates the high dV/dt transients found across the low-side shunt. Industrial-grade -40°C to +85°C operation and the small 28-QFN (4x5) footprint suit compact integrated servo drives where PCB real estate is at a premium.
Recommended
Biomedical Instrumentation and Patient Monitoring
Battery-powered medical devices such as patient monitors, ECGs, and infusion pumps benefit from the LTC2321IUFD-14's wide input dynamic range and dual simultaneous sampling. Its 14-bit + sign dynamic range comfortably captures the +/-5mV to +/-5V bioelectric and pressure-transducer signal range without range-switching relays. The SAR architecture's deterministic latency makes it suitable for paced-event synchronization in cardiac and neurophysiology monitors where sample-time jitter must be sub-microsecond. The exposed-pad 28-QFN (4x5) package provides thermal performance compatible with the heat dissipation limits of sealed plastic medical enclosures without additional heatsinking.
Recommended
Industrial Process Control and PLCs
Programmable logic controllers and distributed I/O modules often require 4-16 channels of +/-10V or 0-20mA analog input, scaled and digitized for backplane transmission. The LTC2321IUFD-14's dual 14-bit + sign channels allow a single part to handle two channels in the 28-QFN (4x5) footprint, doubling channel density versus single-channel ADCs. Its 8VP-P differential input range directly accepts +/-10V after a simple resistor-divider scaling, eliminating the need for an instrumentation front-end in many designs. SPI-compatible outputs interface easily to galvanically-isolated backplanes via digital isolators for industrial EMC compliance.
Recommended
Automatic Test Equipment (ATE) and Instrumentation
Source-measurement units, board-level testers, and benchtop instruments demand accurate, low-latency dual-channel digitization. The LTC2321IUFD-14 provides 14-bit + sign conversion at 2 Msps with deterministic latency - critical for stimulus-response measurements such as loop gain analysis where phase margin depends on sample timing. The differential input architecture rejects common-mode noise from the surrounding digital test rack, while the exposed-pad 28-QFN (4x5) keeps junction temperature rise manageable even at high duty-cycle sampling. Reference design patterns in the LTC2321-14 datasheet (file 232114fc) show how to combine the part with an FPGA for parallel-test multi-channel configurations.
Recommended
Power Quality and Energy Metering
Three-phase revenue-grade energy meters and power-quality analyzers require simultaneous sampling of voltage and current channels to correctly compute true power factor and harmonics. The LTC2321IUFD-14's dual simultaneous sampling at 2 Msps provides sufficient bandwidth for 50th-harmonic analysis on 50/60Hz mains while remaining within EN 50160 and IEC 62053 accuracy envelopes. The 73dB SNR supports Class 0.2S revenue-meter accuracy when paired with a precision reference. The wide 8VP-P differential input range accepts current-transformer and voltage-divider outputs directly, and the small 28-QFN (4x5) enables compact DIN-rail form factors.
Recommended
Recommended Products Summary
Engineering reference data for LTC2321IUFD-14 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LTC2321CUFD-14 | LTC2321HUFD-14 | LTC2320CUFD-16 | LTC2322CUFD-12 | LTC2258CUJ-12 |
|---|---|---|---|---|---|---|
| Package | 28-QFN (4x5) | 28-QFN (4x5) - same | 28-QFN (4x5) - same | 28-QFN (4x5) - same | 28-QFN (4x5) - same | 40-QFN (6x6) - NOT pin-compatible |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Resolution | 14-bit + sign | 14-bit + sign | 14-bit + sign | 16-bit + sign | 12-bit + sign | 12-bit |
| Number of Channels | 2 | 2 | 2 | 2 | 2 | 2 |
| Sample Rate | 2 Msps | 2 Msps | 2 Msps | 1.6 Msps | 2 Msps | 40 Msps |
| Operating Temperature | -40°C to +85°C (industrial) | 0°C to +70°C (commercial) | -40°C to +125°C (automotive) | 0°C to +70°C | 0°C to +70°C | -40°C to +85°C |
| Differential Input Range | 8 VP-P | 8 VP-P | 8 VP-P | 8 VP-P | 8 VP-P | 2 VP-P |
| INL (max) | ±1 LSB | ±1 LSB | ±1 LSB | ±1.25 LSB | ±0.5 LSB | ±1 LSB |
| Interface | SPI / LVDS | SPI / LVDS | SPI / LVDS | SPI / LVDS | SPI / LVDS | LVDS only |
Key Differentiators
- Same 28-QFN (4x5) footprint as LTC2321HUFD-14 and LTC2321CUFD-14 (vs LTC2321HUFD-14)
- 14-bit + sign resolution vs 12-bit for LTC2322CUFD-12 (vs LTC2322CUFD-12)
- Same footprint as LTC2320CUFD-16 - resolution choice without PCB change (vs LTC2320CUFD-16)
Design Notes
Layout the analog input traces as a differential pair with matched lengths and 100Ω characteristic impedance to preserve the LTC2321IUFD-14's 73dB SNR. Tie the QFN exposed pad to a single low-impedance analog ground pour with at least 4 thermal vias, and place the 10µF X7R + 1µF ceramic VDD decoupling within 5mm of pin 10. Per the LTC2321-14 datasheet (232114fc), keep digital switching traces (SCK, SDO) routed on the opposite PCB layer to minimize digital-to-analog crosstalk.
A common pitfall is forgetting to add a 0.1µF ceramic bypass on the REF pin (pin 5) - without it, reference noise couples into both channels and degrades SNR by 5-10dB. Do not leave the LVDS/SDI configuration pins floating; tie them to a defined logic level (GND for SPI, OVDD for LVDS mode) to avoid internal pull-up current. Finally, ensure CNV is held high during power-up to prevent spurious conversions before the supply rail stabilizes.
When using the LVDS digital interface in electrically noisy industrial environments, route the SCK+/SCK- and SDO+/SDO- pairs as 100Ω differential transmission lines on a controlled-impedance inner PCB layer. Series-terminate the driver side near the FPGA and add a 100Ω differential termination at the LTC2321IUFD-14 inputs - the part's LVDS receiver includes internal 100Ω termination but external pads can be used for fine tuning. The Echo Clock (RDLK) should be used to latch data into the FPGA instead of the SCK input to avoid sample-to-sample timing jitter.
Compliance Information
Lead-free (PBF) suffix indicates RoHS-compliant lead-free and lead-free-termination parts per the LTC2321IUFD-14#PBF datasheet designation. AEC-Q100 qualification is NOT available on the LTC2321IUFD-14 industrial grade; choose LTC2321HUFD-14 for automotive (AEC-Q100) applications.
