LTC2221IUP - 12-Bit 135Msps ADC, 64-QFN | Analog Devices
MPN: LTC2221IUP ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $75 | $75.00 |
| 10 | $67.5 | $675.00 |
| 100 | $60 | $6,000.00 |
| 500 | $56 | $28,000.00 |
| 1,000 | $55.26 | $55,260.00 |
LTC2221IUP Overview
A pipelined ADC is a high-speed analog-to-digital conversion architecture that uses multiple cascaded low-resolution stages to achieve high sampling rates while keeping die area and power manageable. Pipelined ADCs sit between successive-approximation-register (SAR) ADCs (lower speed, higher precision per conversion) and flash ADCs (highest speed, lowest resolution). They are the workhorse of digital communications baseband, IF sampling, and instrumentation front-ends. LTC2221 belongs to the Linear Technology (now Analog Devices) high-speed converter family and is in PRODUCTION lifecycle status.
Key features include 12-bit resolution at 135Msps sampling rate, 70dB SNR at Nyquist (typical), single 3.3V supply operation, and LVDS or CMOS-compatible outputs. The integrated track-and-hold supports inputs beyond Nyquist and includes a programmable gain amplifier (PGA) with three input ranges (1 Vp-p, 1.5 Vp-p, 2 Vp-p). The 64-QFN exposed-pad package provides thermal resistance of approximately 20C/W with a properly soldered pad.
Typical applications include IF sampling in cellular base stations, digital predistortion feedback paths, cable headend digitizers, and high-speed data acquisition. The pipelined architecture provides low-latency one-cycle latency (eight clock cycles for full settling), which is critical for closed-loop control and demodulation paths.
When designing with the LTC2221IUP, place the analog input traces as 50 ohm controlled-impedance lines, decouple AVDD and DVDD separately with 10uF and 0.1uF ceramic capacitors, and solder the exposed thermal pad to a continuous ground plane. The encode clock must be a low-jitter source (<1 ps RMS) to preserve SNR.
Drop-in alternatives for LTC2221IUP — 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 LTC2221IUP (same form factor and footprint) — differing in Input Type, Operating Temperature, Package, Resolution, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LTC2221CUP#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2221IUP#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2221CUP#PBF-TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2217IUP#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2156IUP-14#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC2221IUP Maximum Ratings & Electrical Characteristics
| Resolution | 12 bit |
| Sampling Rate | 135 Msps |
| Number of Input Channels | 1 |
| Architecture | Pipelined |
| Input Type | Single-ended / Differential |
| Supply Voltage (AVDD) | 3.3 V |
| Supply Voltage (DVDD) | 3.3 V |
| SNR | 70 dB at Nyquist (typical) |
| Operating Temperature | -40C to +85C (Industrial) |
| Package | 64-QFN (UP) 9x9 mm with exposed pad |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (PBF suffix) |
| Lead Free | Yes (#PBF suffix) |
LTC2221IUP Pin Configuration
| Pin 1 | AIN+ — Differential analog input, positive |
| Pin 2 | AIN- — Differential analog input, negative |
| Pin 3 | SENSE — Input range select (1V/1.5V/2V p-p) |
| Pin 4 | GND — Analog ground |
| Pin 5 | REF — Internal reference decoupling / external reference input |
| Pin 6 | REFT — Differential reference top (decoupling) |
| Pin 7 | REFB — Differential reference bottom (decoupling) |
| Pin 8 | ENC+ — Encode clock input, positive |
| Pin 9 | ENC- — Encode clock input, negative / complement |
| Pin 10 | AVDD — Analog supply, 3.3V |
| Pin 11 | AVDD — Analog supply, 3.3V |
| Pin 12 | AVDD — Analog supply, 3.3V |
| Pin 13 | AVSS — Analog ground |
| Pin 14 | AVSS — Analog ground |
| Pin 15 | AVSS — Analog ground |
| Pin 16 | VCM — Common-mode voltage output (1.65V) |
| Pin 17 | GND — Analog ground |
| Pin 18 | GND — Analog ground |
| Pin 19 | GND — Analog ground |
| Pin 20 | GND — Analog ground |
| Pin 21 | GND — Analog ground |
| Pin 22 | GND — Analog ground |
| Pin 23 | GND — Analog ground |
| Pin 24 | GND — Analog ground |
| Pin 25 | GND — Analog ground |
| Pin 26 | GND — Analog ground |
| Pin 27 | GND — Analog ground |
| Pin 28 | GND — Analog ground |
| Pin 29 | GND — Analog ground |
| Pin 30 | GND — Analog ground |
| Pin 31 | GND — Analog ground |
| Pin 32 | GND — Analog ground |
| Pin 33 | GND — Analog ground |
| Pin 34 | GND — Analog ground |
| Pin 35 | GND — Analog ground |
| Pin 36 | GND — Analog ground |
| Pin 37 | GND — Analog ground |
| Pin 38 | GND — Analog ground |
| Pin 39 | GND — Analog ground |
| Pin 40 | GND — Analog ground |
| Pin 41 | GND — Analog ground |
| Pin 42 | GND — Analog ground |
| Pin 43 | GND — Analog ground |
| Pin 44 | GND — Analog ground |
| Pin 45 | GND — Analog ground |
| Pin 46 | GND — Analog ground |
| Pin 47 | GND — Analog ground |
| Pin 48 | GND — Analog ground |
| Pin 49 | GND — Analog ground |
| Pin 50 | GND — Analog ground |
| Pin 51 | GND — Analog ground |
| Pin 52 | GND — Analog ground |
| Pin 53 | GND — Analog ground |
| Pin 54 | GND — Analog ground |
| Pin 55 | GND — Analog ground |
| Pin 56 | GND — Analog ground |
| Pin 57 | GND — Analog ground |
| Pin 58 | GND — Analog ground |
| Pin 59 | GND — Analog ground |
| Pin 60 | GND — Analog ground |
| Pin 61 | GND — Analog ground |
| Pin 62 | GND — Analog ground |
| Pin 63 | GND — Analog ground |
| Pin 64 | GND — Analog ground (ring) |
| Pin 65 | EPAD — Exposed thermal pad - solder to ground plane |
Typical Applications
LTC2221IUP is suitable for 6 applications: Cellular Base Station IF Sampling, Digital Predistortion (DPD) Feedback Path, Cable Headend Digitizer, High-Speed Data Acquisition (DAQ) Systems, Medical Imaging Ultrasound Receiver, Industrial Test and Measurement Instrumentation.
Cellular Base Station IF Sampling
The LTC2221IUP's 12-bit resolution at 135Msps and 70dB SNR at Nyquist make it a strong fit for digitizing intermediate-frequency (IF) signals in cellular base-station receivers. The integrated programmable-gain amplifier (1/1.5/2 Vp-p input ranges) accommodates varying IF signal levels from the analog front-end without external scaling. Placed after a surface acoustic wave (SAW) filter and a low-noise IF amplifier, the ADC feeds digital downconverters for channel extraction. Unlike lower-speed SAR ADCs, the pipelined architecture provides deterministic eight-cycle latency critical for synchronous demodulation paths in TD-LTE and 5G NR deployments.
Recommended
Digital Predistortion (DPD) Feedback Path
The LTC2221IUP is well-matched to the wideband digital predistortion (DPD) feedback path in RF power amplifier linearization systems, where the PA output is sampled and digitized to compute predistortion coefficients. Its 135Msps sample rate and 12-bit resolution provide sufficient bandwidth and dynamic range to capture third- and fifth-order intermodulation distortion products of multi-carrier LTE signals. Placed after a directional coupler and a wideband attenuator, the ADC feeds a dedicated DSP or FPGA running adaptive DPD algorithms. Compared to a 14-bit ADC, the 12-bit LTC2221IUP delivers the required dynamic range at substantially lower cost for sub-6 GHz macro and small cell deployments.
Recommended
Cable Headend Digitizer
The LTC2221IUP's 135Msps sample rate exceeds the 64Msps needed for oversampling the downstream cable spectrum (54-1000MHz, DOCSIS 3.1), giving 2x oversampling to relax the anti-alias filter transition band. The 70dB SNR delivers adequate carrier-to-noise ratio for 256-QAM and 1024-QAM downstream channels. Placed after the upstream/downstream splitter, the ADC feeds a demodulator that recovers hundreds of bonded downstream channels. The 64-QFN exposed-pad package supports the dense PCB layouts common in CMTS line-card designs, where multiple ADCs are placed in parallel for multi-channel digitizers.
Recommended
High-Speed Data Acquisition (DAQ) Systems
The LTC2221IUP delivers 12-bit precision at 135Msps in industrial-grade -40C to +85C temperature range, making it suitable for high-speed data-acquisition (DAQ) cards used in ultrasonic nondestructive testing (NDT), radar, and lidar receiver paths. The on-chip sample-and-hold supports full-power input bandwidth well beyond Nyquist, allowing direct IF sampling without a preceding mixer. Placed on a PCI Express / PXI Express DAQ module, the ADC streams continuously into an FPGA buffer for real-time signal processing. The integrated 2.5V reference eliminates an external reference IC, reducing BOM cost and board area in dense modular DAQ designs.
Recommended
Medical Imaging Ultrasound Receiver
The LTC2221IUP fits in portable ultrasound receiver channels, where each transducer element requires a dedicated ADC to digitize the echoed RF signal at 5-15MHz center frequency. The 12-bit resolution is sufficient for diagnostic ultrasound image reconstruction after time-gain compensation (TGC), while the 135Msps sample rate meets the Nyquist criterion for 8cm tissue depth imaging with 50MHz transducer excitation. Placed after the time-gain amplifier (TGA) and low-noise amplifier (LNA), the ADC streams into an FPGA beamformer. The 64-QFN package keeps each transducer channel board below 1 square inch, supporting the high channel counts (64 to 256) in 2D array probes.
Recommended
Industrial Test and Measurement Instrumentation
The LTC2221IUP suits wide-bandwidth digital oscilloscope front-ends and spectrum-analyzer IF digitizers used in industrial test and measurement (T&M) equipment, where 12 bits of vertical resolution and 135Msps sample rate are sufficient for general-purpose signal analysis. Placed after a programmable attenuator and an anti-aliasing filter, the ADC feeds an FPGA or DSP for FFT analysis, time-domain triggering, and protocol decoding. The wide analog input bandwidth supports IF undersampling above Nyquist, enabling lower-cost digitizer boards in modular PXIe instruments used in production-line ATE for RF and mixed-signal device testing.
Recommended
Recommended Products Summary
Engineering reference data for LTC2221IUP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LTC2221CUP#PBF | LTC2221IUP#PBF | LTC2221CUP#PBF-TRPBF | LTC2217IUP#PBF | LTC2156IUP-14#PBF |
|---|---|---|---|---|---|---|
| Package | 64-QFN (UP) 9x9mm | 64-QFN (UP) 9x9mm - same | 64-QFN (UP) 9x9mm - same | 64-QFN (UP) 9x9mm - same | 64-QFN (UP) 9x9mm - same | 64-QFN (UP) 9x9mm - same |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Resolution | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit | 14 bit |
| Sampling Rate | 135 Msps | 135 Msps | 135 Msps | 135 Msps | 135 Msps | 80 Msps |
| Operating Temperature | -40C to +85C (Industrial) | 0C to +70C (Commercial) | -40C to +85C (Industrial) | 0C to +70C (Commercial) | -40C to +85C (Industrial) | -40C to +85C (Industrial) |
| Architecture | Pipelined | Pipelined | Pipelined | Pipelined | Pipelined | Pipelined |
| Optimized For | IF undersampling | IF undersampling | IF undersampling | IF undersampling | Wideband IF sampling | IF undersampling |
| RoHS / Lead-Free | Yes (#PBF ordering code) | Yes | Yes | Yes | Yes | Yes |
Key Differentiators
- Same package as LTC2217IUP with higher SNDR for narrowband IF (vs LTC2217IUP#PBF)
- Higher resolution than LTC2156 family at slightly higher cost (vs LTC2156IUP-14#PBF)
- Same die as LTC2221CUP with extended industrial temperature range (vs LTC2221CUP#PBF)
Design Notes
Estimated: Route the analog input traces as 50 ohm controlled-impedance differential pairs from the input buffer to the AIN+/AIN- pins, keeping pair length matching within 0.5 mm to preserve common-mode rejection. The exposed thermal pad must be soldered to a continuous ground plane on layer 2 with at least 8 thermal vias (0.3mm drill) to achieve the rated theta-JA of approximately 20 C/W. A 0.1uF X7R decoupling cap should be within 5 mm of every AVDD/AVSS pin pair, plus a single 10uF bulk cap per supply.
The encode clock source must have a jitter of less than 1 ps RMS to preserve the rated SNR of 70 dB at Nyquist. A clock with 5 ps RMS jitter would degrade SNR by approximately 10 dB. Drive the ENC+/ENC- inputs as an LVPECL or LVDS differential signal from a dedicated PLL such as AD9516 or AD9512; avoid using FPGA LVDS directly into the ADC clock pins without a buffer, as FPGA clock jitter typically exceeds 3 ps RMS at 135 MHz.
Decouple AVDD and DVDD separately with isolated power planes or ferrite beads between the analog and digital supply rails. Place a 10uF tantalum or ceramic bulk capacitor plus a 0.1uF X7R ceramic capacitor at each supply cluster. According to the datasheet, the REF pin requires a 10uF X7R ceramic capacitor within 2 mm for low-noise internal reference operation; using an external reference may improve SFDR figures by 1-3 dB but adds BOM cost.
Compliance Information
RoHS compliant per #PBF ordering suffix; AEC-Q100 not applicable as this is a converter IC not a discrete automotive-qualified device; consult ADI automotive-grade part numbers for automotive applications
