Analog Devices Inc. LTC2157IUP-14#PBF

Overview

LTC2157IUP-14#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, 14-bit, 250Msps simultaneous-sampling analog-to-digital converter optimized for high-frequency signal digitization in communications infrastructure. It delivers 70dB SNR, 90dB SFDR, 1.25GHz full-power bandwidth, and operates from a single 1.8V supply with DDR LVDS outputs. It is deployed in cellular basestations and software-defined radios requiring wide dynamic range and undersampling capability.

For engineers reviewing the LTC2157IUP-14#PBF datasheet, LTC2157IUP-14#PBF pinout, LTC2157IUP-14#PBF application, or LTC2157IUP-14#PBF equivalent, key selection criteria include its guaranteed –40°C to +85°C industrial temperature grade, 6-cycle pipeline latency, optional clock duty cycle stabilizer, serial SPI configuration interface, and compatibility with 1.5VP-P differential analog inputs.

Technical Context

The LTC2157IUP-14#PBF implements a pipelined ADC architecture with integrated sample-and-hold (S/H) front-end and correction logic, enabling simultaneous sampling across two channels with 6-clock-cycle latency. Its 1.25GHz input bandwidth supports RF undersampling of IF and RF signals up to 907MHz while maintaining 70dB SNR at 250Msps.

Digital output uses double-data-rate (DDR) LVDS signaling with programmable 1.75mA or 3.5mA current per differential pair and on-chip 100Ω termination. Clocking accepts differential ENC+/ENC– inputs (sine, PECL, LVDS, TTL, CMOS), and includes an optional duty cycle stabilizer to maintain performance across non-50% duty cycles.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD9689-2600EBZ, the LTC2157IUP-14#PBF offers superior thermal efficiency and simpler power delivery in a smaller QFN, while compared with LTC2268IUP-14#PBF, it delivers 2.4× higher sampling rate with identical footprint and interface - enabling upgrade paths without PCB redesign.

Availability

LTC2157IUP-14#PBF is available at Aetrix Electronics and suitable for cellular basestations, software-defined radios, and medical ultrasound systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LTC2157IUP-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 DSP solutions for precision instrumentation, communications, and industrial applications.

The LTC2157-14 series belongs to Linear's high-speed ADC product line, designed specifically for wideband communications infrastructure where dynamic range, sampling fidelity, and thermal efficiency are critical in space-constrained, high-reliability environments.

FAQ

What is the operating temperature range of the LTC2157IUP-14#PBF?

The LTC2157IUP-14#PBF is rated for industrial operation from –40°C to +85°C, as confirmed by its "I" grade designation and Absolute Maximum Ratings table. This range is validated across all key specifications including SNR, SFDR, INL, and power consumption - making it suitable for outdoor basestations and ruggedized test equipment where ambient temperatures fluctuate widely.

Does the LTC2157IUP-14#PBF support external voltage reference operation?

Yes, the LTC2157IUP-14#PBF supports external reference operation via the SENSE pin (Pin 7). Applying 1.200V–1.300V to SENSE selects an input range of ±0.6 × VSENSE, enabling precise gain scaling and improved system-level accuracy when paired with a low-drift external reference such as the LT6655. Internal reference mode (SENSE tied to VDD) yields ±0.75V range.

How is the DDR LVDS output current configured on the LTC2157IUP-14#PBF?

The DDR LVDS output current on the LTC2157IUP-14#PBF is configurable via the SDI pin in parallel programming mode (PAR/SER = VDD) or through SPI register writes in serial mode. Two settings are supported: 1.75mA (lower power, ~125mV differential swing) or 3.5mA (higher noise immunity, ~350mV differential swing), both compliant with ANSI TIA/EIA-644-A LVDS standards.

What is the purpose of the OF+/OF– pins on the LTC2157IUP-14#PBF?

The OF+/OF– (Pins 22/23) are differential over/underflow flag outputs that indicate saturation events in either Channel A or Channel B. OF+ goes high when any conversion result exceeds the 14-bit signed two's complement range (i.e., codes < 0x0000 or > 0x3FFF). This real-time flag enables immediate AGC adjustment or clipping detection without parsing full data streams.

Can the LTC2157IUP-14#PBF be used without the internal clock duty cycle stabilizer?

Yes, the LTC2157IUP-14#PBF operates fully functional with the clock duty cycle stabilizer disabled. When CS = low and duty cycle stabilizer is off, ENC+/ENC– timing requirements relax to t_L/t_H ≥ 1.9ns (min), allowing use with standard LVDS or CMOS clocks. Enabling the stabilizer (CS = high) extends tolerance to 1.5ns–50ns, supporting asymmetric clocks from PLLs or crystal oscillators with poor duty cycle control.