Texas Instruments SN761634RTWR

Overview

SN761634RTWR from Texas Instruments is a single-chip FM stereo transmitter IC designed for portable audio systems. It operates across 76–108 MHz, supports I²C or parallel control, delivers up to +4 dBm RF output power, integrates a fourth-order 15-kHz low-pass filter, and accepts stereo analog inputs (L_IN/R_IN) with programmable pre-emphasis and modulation depth. It targets compact wireless audio broadcast applications.

For engineers reviewing the SN761634RTWR datasheet, SN761634RTWR pinout, SN761634RTWR application, or SN761634RTWR equivalent, this page provides verified functional specifications, validated terminal roles, confirmed package mapping to 24-pin WQFN (RTW), and real-world design context for integration into battery-powered FM transmitters.

Technical Context

The SN761634RTWR implements a fully integrated PLL-based FM synthesis architecture using a 32.768-kHz crystal reference to generate VCO frequencies from 150–217 MHz, divided down to 76–108 MHz RF output. Its dual-mode interface (I²C via SDA/SCL or 5-bit parallel via D0–D4) enables flexible host controller integration in resource-constrained devices.

It features independent analog signal paths: left/right audio inputs feed a stereo MPX encoder with selectable 50/75-ms pre-emphasis, pilot tone generation (adjustable ±6 dB), and composite modulation control (MODADJ[3:0], PLTADJ[2:0]). RF output is tunable via 14-bit N-divider programming and supports four discrete TX power levels (–7, –3, +1, +4 dBm) with corresponding external pull-up resistors on TX_OUT.

Key Specifications

Pinout & Package

SN761634RTWR is housed in a 24-pin Wettable Flank Quad Flat No-Lead (WQFN) package, 4 mm × 4 mm, 0.5 mm pitch (TI package code RTW). Thermal pad exposed on underside for enhanced heat dissipation in portable enclosures.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar FM transmitter applications.

Compared with Si4713-B20-GM and MAX2112ETJ+, the SN761634RTWR delivers a purpose-built, cost-optimized FM stereo solution with zero external encoding components, dual-mode control, and guaranteed 15-kHz audio fidelity - ideal for consumer audio accessories where integration, footprint, and ease of certification are primary concerns.

Availability

SN761634RTWR is available at Aetrix Electronics and suitable for portable audio transmitters, personal navigation devices, MP3 player accessories, and portable media players requiring stable component supply and legacy FM broadcast compatibility.

Supply support for SN761634RTWR 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

Texas Instruments is a global semiconductor company specializing in analog, embedded processing, and connectivity technologies with over 90 years of innovation in high-reliability signal chain solutions.

The SN761634RTWR belongs to TI's legacy audio broadcast product line, engineered specifically for ultra-compact, battery-powered FM stereo transmitters in consumer electronics - emphasizing integration, low quiescent current, and regulatory-ready RF performance.

FAQ

What is the operating voltage range for the SN761634RTWR?

The SN761634RTWR operates from 2.5 V to 4.0 V on both VCC and VCC_OSC pins. This range aligns with single-cell Li-ion/Li-poly battery voltages, enabling direct integration into portable devices without voltage regulation. Operation outside this range risks damage or undefined behavior per Absolute Maximum Ratings.

How does the SN761634RTWR achieve FM stereo encoding?

The SN761634RTWR performs full stereo MPX encoding internally: it sums and differences left/right audio, generates a 19-kHz pilot tone, applies 50/75-ms pre-emphasis, and combines all signals into a composite baseband. No external encoder IC or passive components are required - the MPX_FIL pin connects only to a loop filter capacitor.

Can the SN761634RTWR be used without a crystal?

Yes - the SN761634RTWR supports external clock injection: leave XTAL1 open and apply a 32.768-kHz sine (500 mVpp–2 Vpp) or square wave (200 mVpp–2 Vpp) to XTAL2. This bypasses the internal crystal oscillator circuit while maintaining precise frequency reference for PLL stability.

What are the thermal considerations for the SN761634RTWR in a 4×4 mm WQFN package?

The SN761634RTWR's RTW package includes an exposed thermal pad on the bottom. For reliable operation at +4 dBm output (24 mA ICC), TI recommends soldering the pad to a minimum 100 mm² copper pour with ≥4 thermal vias to inner ground planes. Junction-to-ambient thermal resistance is ~80°C/W under standard JEDEC conditions.

Is the SN761634RTWR still in production?

No - according to TI's official packaging addendum, SN761634RTWR is marked OBSOLETE. However, Aetrix Electronics maintains legacy inventory with full traceability and supports design-in continuity through lifecycle management, including obsolescence forecasting and last-time-buy coordination for active production programs.