Texas Instruments DF1704E

Overview

DF1704E from Texas Instruments is a high-performance, stereo, 8× oversampling digital interpolation filter IC designed for precision audio signal conditioning in high-end DAC-based systems. It supports 24-bit resolution, 96kHz sampling, ±0.00005dB passband ripple, –115dB stopband attenuation, and operates on a single +5V supply in SSOP-28 package - deployed as the companion filter to PCM1704 DACs in audiophile-grade CD players and studio converters.

For engineers reviewing the DF1704E datasheet, DF1704E pinout, DF1704E application, or DF1704E equivalent, key selection criteria include its programmable sharp/slow roll-off filter response, hardware/software mode control interface, I²S/standard/left-justified input format support, 16–24-bit selectable word lengths, and de-emphasis functionality for 32/44.1/48kHz sample rates.

Technical Context

The DF1704E implements a fixed-coefficient FIR interpolation filter with 8× oversampling architecture, generating output data at 256f_S, 384f_S, 512f_S, or 768f_S system clock rates. Its internal timing engine synchronizes BCKIN, LRCIN, and XTI inputs using automatic clock detection logic that tolerates up to ±6 bit-clock phase misalignment.

It features dual-mode configuration: hardware mode uses dedicated pins (I2S, IW0/IW1, OW0/OW1, SRO, DEM, SF0/SF1) for static setup; software mode employs a 3-wire serial port (ML/MC/MD) to program four 16-bit registers controlling attenuation, mute, de-emphasis, filter roll-off, and data format - all operating with MSB-first, two's complement, right-justified output.

Key Specifications

Pinout & Package

DF1704E is housed in a 28-pin SSOP (Shrink Small Outline Package) with 0.65mm lead pitch, optimized for high-density audio PCB layouts and thermal performance in compact enclosures.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital interpolation filter applications.

Compared with TAS3103IDBTR and AK4128VN, the DF1704E uniquely combines dedicated 8× oversampling architecture, on-chip crystal oscillator, dual hardware/software configuration, and –115dB stopband attenuation - making it irreplaceable in legacy high-fidelity DAC designs where timing simplicity and analog filter relaxation are critical.

Availability

DF1704E is available at Aetrix Electronics and suitable for high-fidelity CD transports, digital audio workstation interfaces, and studio mastering converters requiring stable component supply and long-term obsolescence management.

Supply support for DF1704E 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 specializing in analog, embedded processing, and high-performance signal chain solutions for industrial, automotive, and audio markets.

The DF1704E belongs to TI's premium audio digital filter product line, engineered specifically to enable reference-grade audio playback systems by delivering ultra-low distortion, precise timing, and seamless interoperability with TI's PCM-series DACs.

FAQ

What is the primary function of the DF1704E in an audio system?

The DF1704E serves as a high-precision digital interpolation filter that performs 8× oversampling on incoming stereo audio data before delivery to a DAC like the PCM1704. Its core function is to suppress imaging artifacts above the Nyquist frequency while preserving passband integrity - enabling simpler analog reconstruction filters and higher fidelity playback. The DF1704E achieves this with –115dB stopband attenuation and ±0.00005dB passband ripple, making it essential in high-end audio signal chains.

Does the DF1704E support 96kHz operation, and what are the clocking constraints?

Yes, the DF1704E fully supports 96kHz sampling, but with specific clocking limitations: the 768f_S system clock option is prohibited at 96kHz, and the on-chip crystal oscillator cannot exceed 24.576MHz - meaning 96kHz operation at 256f_S (24.576MHz) requires an external clock applied to XTI. The DF1704E's clock detection circuit automatically identifies the multiplier (256/384/512) based on the ratio between XTI and LRCIN, ensuring robust synchronization even with moderate phase skew.

How does the DF1704E handle digital de-emphasis, and which sample rates are supported?

The DF1704E implements precise digital de-emphasis with ±0.003dB error for 32kHz, 44.1kHz, and 48kHz sampling rates - selected via SF0/SF1 pins or MODE3 register. It applies the standard 50/15µs RIAA-derived curve directly in the digital domain, eliminating the need for analog RC networks and associated component tolerance errors. De-emphasis is disabled by default and activated only when DEM = HIGH (hardware) or DEM = 1 (software), ensuring compatibility with non-de-emphasized sources.

Can the DF1704E be used with DACs other than the PCM1704?

Yes, the DF1704E is compatible with any 24-bit audio DAC accepting right-justified, MSB-first, two's complement serial input synchronized to BCKO and WCKO clocks - including TI's PCM1794, AKM's AK4396, or Cirrus Logic's CS4398. Its output interface (256f_S/192f_S BCKO, 8f_S WCKO) and programmable word length (16/18/20/24-bit) ensure broad interoperability. However, optimal performance is achieved with DACs sharing TI's timing architecture, as validated in the DF1704E's reference designs.

What are the key differences between hardware and software mode on the DF1704E?

In hardware mode (MODE = LOW), configuration is set via dedicated pins (I2S, IW0/IW1, OW0/OW1, SRO, DEM, etc.), enabling fixed-function operation without host processor involvement. In software mode (MODE = HIGH), a 3-wire serial port (ML/MC/MD) writes to four internal 16-bit registers (MODE0–MODE3) for dynamic control of attenuation, mute, de-emphasis, and format - allowing real-time adjustments. Both modes support identical core functions, but software mode adds independent L/R volume control and runtime reconfiguration capability not available in hardware mode.