Analog Devices Inc. LTC2157CUP-14#PBF

Overview

LTC2157CUP-14#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, 14-bit, 250Msps analog-to-digital converter with DDR LVDS outputs, 1.25GHz full-power bandwidth, 70dB SNR, and 90dB SFDR. It operates from a single 1.8V supply and supports easy-to-drive 1.5VP-P differential analog inputs. This ADC is engineered for high-performance communications systems requiring undersampling of RF signals.

For engineers reviewing the LTC2157CUP-14#PBF datasheet, LTC2157CUP-14#PBF pinout, LTC2157CUP-14#PBF application, or LTC2157CUP-14#PBF equivalent, key selection criteria include sampling rate headroom at 250Msps, low-latency 6-cycle pipeline, integrated clock duty cycle stabilizer, and compatibility with 9mm × 9mm QFN PCB layouts.

Technical Context

The LTC2157CUP-14#PBF implements a pipelined 14-bit ADC architecture with simultaneous sampling across two channels, enabling coherent I/Q digitization. Its sample-and-hold front-end delivers 1.25GHz full-power bandwidth and 0.15psRMS acquisition jitter, supporting direct RF sampling up to Nyquist-limited frequencies.

Digital interface logic includes a configurable SPI port for mode control and DDR LVDS output drivers with programmable 1.75mA/3.5mA current per pair. The device integrates an optional clock duty cycle stabilizer and supports sleep (<5mW) and nap (213mW) power modes without sacrificing timing accuracy.

Key Specifications

Pinout & Package

64-pin (9mm × 9mm) plastic QFN package with exposed thermal pad (Pin 65 = GND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel, high-speed ADC applications.

Compared with AD9689BCPZ-2600 and LTC2268IUP-14#PBF, the LTC2157CUP-14#PBF uniquely balances 250Msps dual-channel performance, DDR LVDS simplicity, and 650mW power in a compact QFN - making it optimal for space-constrained, medium-bandwidth RF digitizers where JESD204B overhead is unjustified.

Availability

LTC2157CUP-14#PBF is available at Aetrix Electronics and suitable for cellular basestation receiver design, software-defined radio development, and high-definition medical imaging systems requiring stable component supply and long-term production continuity.

Supply support for LTC2157CUP-14#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 RF ICs, serving precision instrumentation, communications, and industrial markets.

The LTC2157CUP-14#PBF belongs to Linear's high-speed ADC product line, designed specifically for demanding RF/IF digitization in wireless infrastructure, defense electronics, and scientific instrumentation where dynamic range and timing fidelity are critical.

FAQ

What is the operating temperature range for the LTC2157CUP-14#PBF?

The LTC2157CUP-14#PBF is specified for commercial-grade operation from 0°C to +70°C. This is confirmed by the "C" suffix in the part number and the order information table listing "0°C to 70°C" for all C-grade variants including LTC2157CUP-14#PBF. Industrial-grade alternatives (e.g., LTC2157IUP-14#PBF) extend to –40°C to +85°C.

Does the LTC2157CUP-14#PBF support both internal and external voltage references?

Yes, the LTC2157CUP-14#PBF supports both reference modes via the SENSE pin. Connecting SENSE to VDD selects the internal 1.25V reference and sets the input range to ±0.75V. Applying an external 1.2V–1.3V reference to SENSE configures the input range to ±0.6 × V_SENSE, as documented in the Analog Input section and PIN FUNCTIONS description.

How many data bits does each LVDS pair carry on the LTC2157CUP-14#PBF?

Each LVDS output pair on the LTC2157CUP-14#PBF carries two data bits in double-data-rate (DDR) format. For example, DA0_1+ and DA0_1– transmit DA0 (even) when CLKOUT+ is low and DA1 (odd) when CLKOUT+ is high - a configuration explicitly defined in the PIN FUNCTIONS section for both Channel A and Channel B outputs.

What is the purpose of the PAR/SER pin on the LTC2157CUP-14#PBF?

The PAR/SER pin (Pin 63) selects the programming interface mode: grounded for serial SPI configuration (using CS, SCK, SDI, SDO), or tied to VDD for parallel mode where CS, SCK, and SDI become direct logic inputs controlling basic functions like LVDS current and duty cycle stabilizer. This dual-mode flexibility is detailed in the PIN FUNCTIONS section.

Can the LTC2157CUP-14#PBF operate with a non-50% duty cycle clock?

Yes, the LTC2157CUP-14#PBF includes an optional clock duty cycle stabilizer (DCS) that corrects input clock asymmetry. When enabled via the CS pin in parallel mode or SPI register in serial mode, the DCS allows full 250Msps performance even with duty cycles as low as 40% or as high as 60%, as verified in the FEATURES list and TIMING CHARACTERISTICS table.