Analog Devices Inc. LTC5540IUH#TRPBF

Overview

LTC5540IUH#TRPBF from Analog Devices (acquired Linear Technology) is a high-dynamic-range passive downconverting mixer optimized for 600MHz–1.3GHz RF input with 700MHz–1.2GHz LO range and 5MHz–500MHz IF output. It delivers 7.9dB conversion gain, 25.9dBm IIP3, and 9.9dB noise figure at 900MHz in high-side LO configuration, targeting LTE/GSM receiver front-ends requiring wideband selectivity and blocking resilience.

For engineers reviewing the LTC5540IUH#TRPBF datasheet, LTC5540IUH#TRPBF pinout, LTC5540IUH#TRPBF application, or LTC5540IUH#TRPBF equivalent, key selection criteria include its dual-LO SPDT switch with 50dB isolation, 50Ω single-ended RF/LO interfaces, differential open-collector IF outputs, shutdown control, and 20-lead 5mm × 5mm QFN package with exposed thermal pad.

Technical Context

The LTC5540IUH#TRPBF integrates a passive double-balanced mixer core, high-speed SPDT LO switch, LO buffer amplifier, and differential IF amplifier with adjustable bias. Its RF input uses an integrated transformer with center-tap (CT) pin for impedance tuning, while LO inputs are internally matched to 50Ω across 700–1200MHz regardless of shutdown state.

It supports both high-side (f_LO = f_RF + f_IF) and low-side (f_LO = f_RF – f_IF) injection, with conversion gain flatness ±0.20dB over 900±30MHz and temperature coefficient –0.008dB/°C. The IF amplifier operates from 3.3V or 5V supply, enabling P1dB extension from 11dBm to 14.5dBm.

Key Specifications

Pinout & Package

The LTC5540IUH#TRPBF is housed in a 20-lead 5mm × 5mm plastic QFN (UH package) with exposed thermal pad (Pin 21) soldered to PCB ground for thermal and electrical performance. Pin 1 is NC; pins 4, 10, 12, 13, 17, and 21 are GND.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar downconverting mixer applications.

Compared with HMC1040LP4CE and MAX2031ETX+, the LTC5540IUH#TRPBF uniquely combines integrated IF amplification, dual-LO SPDT switching, and 25.9dBm IIP3 in a single 20-lead QFN-reducing bill-of-materials count by up to 7 components versus discrete alternatives.

Availability

LTC5540IUH#TRPBF is available at Aetrix Electronics and suitable for cellular infrastructure, point-to-point microwave links, and high-dynamic-range receiver designs requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LTC5540IUH#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, acquired Linear Technology in 2017 to strengthen RF and precision signal chain offerings.

The LTC5540IUH#TRPBF belongs to ADI's high-dynamic-range mixer product line, designed specifically for wireless infrastructure receivers demanding exceptional linearity, low noise, and integrated functionality in compact form factors.

FAQ

What is the recommended LO drive level for optimal performance of the LTC5540IUH#TRPBF?

The LTC5540IUH#TRPBF is optimized for 0dBm LO drive across its 700–1200MHz range, delivering 7.9dB conversion gain and 25.9dBm IIP3 at 900MHz. Performance remains robust within ±6dBm; however, LO power exceeding +6dBm risks ESD diode conduction. The internal limiting amplifiers maintain consistent gain flatness and noise figure across this range, making the LTC5540IUH#TRPBF tolerant of synthesizer output variations.

Can the LTC5540IUH#TRPBF operate with both high-side and low-side LO injection?

Yes, the LTC5540IUH#TRPBF supports both high-side (f_LO = f_RF + f_IF) and low-side (f_LO = f_RF – f_IF) LO injection. For high-side operation at 900MHz RF, use 1090MHz LO with 190MHz IF; for low-side, use 710MHz LO. Conversion gain flatness is ±0.20dB (high-side) and ±0.33dB (low-side) over 900±30MHz, and IIP3 remains above 23.4dBm in both configurations-enabling flexible system architecture choices without redesigning the LTC5540IUH#TRPBF interface.

How does the shutdown function affect LO port matching on the LTC5540IUH#TRPBF?

Unlike most mixers, the LTC5540IUH#TRPBF maintains 50Ω LO input matching on both LO1 and LO2 ports even when SHDN is asserted high (shutdown mode). This eliminates the need for external termination resistors during power-down states, preserving system-level impedance integrity and simplifying RF switch matrix design. The shutdown current drops to 500µA while LO port return loss remains >12dB across 700–1200MHz-ensuring predictable behavior in TDD or burst-mode applications using the LTC5540IUH#TRPBF.

What is the purpose of the CT (center-tap) pin on the LTC5540IUH#TRPBF?

The CT (Pin 3) on the LTC5540IUH#TRPBF provides access to the center-tap of the integrated RF transformer secondary winding. It carries a nominal 1.2V DC bias and requires a bypass capacitor to ground for high-frequency decoupling-critical for stabilizing RF input impedance across frequency. Placement within 2mm of Pin 3 is mandatory for effective decoupling; capacitor value is LO-frequency-dependent (e.g., 1.5pF for low-side, 5.6pF for high-side LO). This feature enables broadband RF matching without external baluns, a key enabler of the LTC5540IUH#TRPBF's compact solution size.

Does the LTC5540IUH#TRPBF require external matching components for 50Ω RF input?

Yes, the LTC5540IUH#TRPBF requires a series DC-blocking capacitor (e.g., 5.6pF for high-side LO) at the RF input (Pin 2) to achieve >12dB return loss across 600–1300MHz. This capacitor compensates for the transformer's frequency-dependent impedance and blocks DC from RF sources. No additional shunt elements are needed-the integrated transformer and internal topology enable full 50Ω matching with a single capacitor, reducing external component count versus traditional double-balanced mixers and simplifying layout for the LTC5540IUH#TRPBF.