Analog Devices Inc. LTC6948IUFD-2#TRPBF

Overview

LTC6948IUFD-2#TRPBF from Analog Devices is an ultralow-noise 3.08GHz to 4.91GHz fractional-N PLL synthesizer with integrated VCO, 4th-order ΔΣ modulator, 18-bit fractional denominator, and programmable output divider (1–6). It delivers –225 dBc/Hz normalized in-band phase noise floor and –274 dBc/Hz 1/f noise for microwave data links and secure radio LO generation.

For engineers reviewing the LTC6948IUFD-2#TRPBF datasheet, LTC6948IUFD-2#TRPBF pinout, LTC6948IUFD-2#TRPBF application, or LTC6948IUFD-2#TRPBF equivalent, this page provides verified frequency range (3.08–4.91 GHz), VCO tuning sensitivity (4.7–7.0 %/V), reference input support up to 425 MHz, fast switching capability, and confirmed QFN-28 (4mm × 5mm) package with exposed thermal pad.

Technical Context

The LTC6948IUFD-2#TRPBF implements a fully integrated PLL architecture with reference divider (1–31), phase-frequency detector, ultralow-noise charge pump (1–11.2 mA, ±3.5% matching), and fractional feedback divider using a 4th-order ΔΣ modulator to suppress spurs. Its VCO operates natively at 3.08–4.91 GHz and is divided by integer values 1–6 to produce RF outputs from 0.513 GHz to 4.91 GHz.

It supports differential reference input (10–425 MHz, 0.5–2.7 V_P-P), SPI-controlled configuration via CS/SCLK/SDI/SDO, RF output muting (110 ns enable time), and dual supply domains: 3.3 V for digital/RF sections and 5 V for VCO/charge pump. The device requires external loop filter on CP and TUNE pins and mandates proper bypassing of all supply pins per layout guidelines.

Key Specifications

Pinout & Package

Package: 28-lead (4 mm × 5 mm) plastic QFN (UFD) with exposed thermal pad (Pin 29 = GND, must be soldered to PCB ground plane).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fractional-N PLL synthesizer applications.

Compared with HMC703LP4E and ADF4371BCPZ, the LTC6948IUFD-2#TRPBF uniquely balances 4.91 GHz native VCO range, –225 dBc/Hz phase noise floor, and full integration-including calibrated VCO and ΔΣ LDO-making it optimal for compact, high-performance microwave LO generation where spectral purity and board space are critical.

Availability

LTC6948IUFD-2#TRPBF is available at Aetrix Electronics and suitable for wireless basestations, microwave data links, and secure radio systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LTC6948IUFD-2#TRPBF 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 is a global leader in high-performance analog, mixed-signal, and RF ICs, serving communications, industrial, automotive, and aerospace markets with precision timing and signal processing solutions.

The LTC6948 product line delivers ultralow-noise fractional-N synthesizers with integrated VCOs for demanding microwave and millimeter-wave applications where phase noise, spurious performance, and frequency agility are critical.

FAQ

What is the exact VCO frequency range supported by the LTC6948IUFD-2#TRPBF?

The LTC6948IUFD-2#TRPBF supports a native VCO frequency range of 3.08 GHz to 4.91 GHz, as specified in the "Available Options" table and confirmed in Electrical Characteristics (f_VCO MIN/MAX for LTC6948-2). This range is factory-trimmed and calibrated; operation outside this band is not guaranteed and may result in unlock or degraded phase noise.

Does the LTC6948IUFD-2#TRPBF support differential reference input, and what are the AC-coupling requirements?

Yes, the LTC6948IUFD-2#TRPBF supports differential reference input on REF+ (Pin 1) and REF– (Pin 28). Both pins must be AC-coupled using 1 µF capacitors. If used single-ended with VREF+ ≤ 2.7 V_P-P, REF– must be bypassed to GND with a 1 µF capacitor; for VREF+ > 2.7 V_P-P, a 47 pF capacitor is required. Input slew rate must exceed 20 V/µs.

What is the maximum reference input frequency the LTC6948IUFD-2#TRPBF can accept?

The LTC6948IUFD-2#TRPBF accepts reference input frequencies up to 425 MHz, as stated in the Electrical Characteristics table under "fREF Input Frequency". This high reference capability enables wide loop bandwidths (>180 kHz) for fast frequency settling and reduced integrated phase noise in fractional mode.

How does the output divider (O_DIV) affect the final RF output frequency of the LTC6948IUFD-2#TRPBF?

The LTC6948IUFD-2#TRPBF's programmable output divider (O_DIV = 1 to 6) divides the VCO output to generate the final RF frequency. For example, with VCO = 4.0 GHz and O_DIV = 2, RF output = 2.0 GHz. The device maintains 50% duty cycle and matched rise/fall times across all divider settings, ensuring consistent mixer LO drive performance.

Is the LTC6948IUFD-2#TRPBF pin-compatible with other variants in the LTC6948 family, such as LTC6948IUFD-1#TRPBF or LTC6948IUFD-4#TRPBF?

Yes, all UFD-package variants-including LTC6948IUFD-1#TRPBF, LTC6948IUFD-2#TRPBF, LTC6948IUFD-3#TRPBF, and LTC6948IUFD-4#TRPBF-are pin-compatible and share identical QFN-28 (4 mm × 5 mm) footprint, pinout, and supply requirements. Only the internal VCO frequency range differs; no PCB changes are required when substituting between variants.