Texas Instruments SN761677DBTR

Overview

SN761677DBTR from Texas Instruments is a single-chip TV/VCR tuner IC integrating VHF-L/VHF-H/UHF 3-band local oscillators, mixer, PLL synthesizer, 30-V DC/DC converter for tuning amplifier bias, four NPN emitter-follower band switch drivers, and four NPN open-collector ports. It operates from a 5-V supply, uses I²C bus control (100–400 kHz), and delivers 26 dB typical conversion gain across 55–804 MHz RF input range in a 38-pin TSSOP package.

For engineers reviewing the SN761677DBTR datasheet, SN761677DBTR pinout, SN761677DBTR application, or SN761677DBTR equivalent, this page provides verified technical context, validated pin functions, confirmed RF/IF performance metrics, real-world band-switching behavior, and direct alternatives for legacy TV tuner redesigns requiring integrated DC/DC and I²C-controlled synthesis.

Technical Context

The SN761677DBTR implements a 15-bit programmable counter with selectable reference divider ratios (512/640/1024) to support 4-MHz crystal-based PLL tuning across VHF-L (55–136 MHz), VHF-H (133–364 MHz), and UHF (367–804 MHz) bands. Its integrated 30-V DC/DC converter (VDC output) supplies tuning voltage (VTU) to external varactor diodes with 100-ms settling time after power-up.

I²C interface (SCL/SDA/AS) enables full configuration of band selection (BS1–BS4), port states (P5–P8), charge pump current (CP), and reference ratio (RSA/RSB). The device includes on-die 5-level ADC (ADC/TEST pin) and status reporting (POR/FL flags), with all oscillator sections isolated via dedicated ground pins (OSC GND, RF GND, IF GND, TUGND) to minimize coupling.

Key Specifications

Pinout & Package

SN761677DBTR is housed in a 38-pin TSSOP package (DBT drawing), measuring 12.5 mm × 6.1 mm × 1.2 mm, with 0.65-mm lead pitch and exposed thermal pad (not electrically connected).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar TV/VCR tuner applications.

Compared with SN761677DBTR, SN761676DBTR sacrifices UHF capability for lower cost in VHF-only applications, while TA2081FNG trades I²C simplicity and integrated DC/DC for superior oscillator spectral purity - making SN761677DBTR optimal for cost-sensitive, full-band, single-supply tuner modules.

Availability

SN761677DBTR is available at Aetrix Electronics and suitable for analog TV tuner modules, VCR RF front-ends, and legacy broadcast receiver retrofits requiring stable component supply and long-term obsolescence management.

Supply support for SN761677DBTR 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 leader founded in 1930, specializing in analog, embedded processing, and connectivity technologies with broad industrial and consumer application reach.

The SN761677DBTR belongs to TI's legacy TV tuner IC product line, engineered specifically for cost-effective, single-chip analog broadcast signal reception in consumer electronics before the digital transition.

FAQ

What is the function of the VDC pin on the SN761677DBTR?

The VDC pin on the SN761677DBTR is the DC/DC converter monitor output, not a power output. It provides a buffered version of the internal 30-V DC/DC switching node for external capacitor filtering. Per the datasheet, it must connect only to a capacitor (no resistive load or routing to other circuits) to stabilize the converter and prevent oscillation. This pin is critical for achieving specified 35-V minimum output on VTU.

Does the SN761677DBTR support I²C repeated START conditions?

Yes, the SN761677DBTR supports I²C repeated START conditions as defined in the standard I²C specification. The timing chart (Figure 1) confirms th(STA) ≥ 0.6 µs and tBUF ≥ 1.3 µs, meeting the minimum bus-free time requirement for repeated START. This allows continuous register reads/writes without releasing the bus, enabling efficient configuration of multiple parameters (e.g., divider bytes and control byte) in one transaction.

Can the SN761677DBTR operate with a crystal frequency other than 4 MHz?

No, the SN761677DBTR is designed exclusively for use with a 4-MHz fundamental-mode crystal, as confirmed by the "Crystal oscillator" parameter (FXTAL = 4 MHz) and associated test conditions in the Electrical Characteristics table. The internal oscillator circuit, prescaler ratios (1/32, 1/33), and PLL architecture are optimized for this frequency; using any other crystal value will result in incorrect tuning step resolution and failure to achieve lock across the specified VHF/UHF bands.

How is band selection implemented on the SN761677DBTR?

Band selection on the SN761677DBTR is controlled via the BS1–BS4 pins (terminals 31, 30, 29, 28), which are NPN emitter-follower outputs. According to Table 3, BS1=1/BS2=0/BS4=0 selects VHF-L; BS1=x/BS2=1/BS4=0 selects VHF-H; and BS1=x/BS2=x/BS4=1 selects UHF. These outputs drive external band-switch networks (e.g., PIN diodes or relays), and their logic state is set through the I²C Ports byte (PB), not hardwired.

What is the maximum allowable tuning voltage (VTU) load current for the SN761677DBTR?

The SN761677DBTR's VTU pin is rated for a maximum load current of 230 µA, as specified under "IC(VDCM) Output current (VDC)" in the Electrical Characteristics table. Exceeding this current causes output voltage droop below the 35-V minimum, degrading varactor tuning range and potentially causing loss of lock. Designers must ensure external tuning networks (e.g., varactor bias resistors) draw ≤230 µA total - typically achieved with >130-kΩ equivalent resistance to 30 V.