NXP Semiconductors MC145483DW

Overview

MC145483DW from Freescale Semiconductor is a 13-bit linear PCM codec-filter IC designed for voice digitization and reconstruction in digital telephony systems. It integrates differential analog signal processing, on-chip transmit band-pass (200–3400 Hz) and receive low-pass (3400 Hz) filters, 2's complement data interface, and an internal 0.886 V precision reference voltage. It operates from a single 3 V supply with typical power dissipation of 8 mW and supports both synchronous and asynchronous clocking modes.

For engineers reviewing the MC145483DW datasheet, MC145483DW pinout, MC145483DW application, or MC145483DW equivalent, key selection considerations include its fully-differential analog architecture for >75 dB dynamic range, programmable receive gain control (0 to –21 dB in 3 dB steps), high-impedance VAG reference for noise-sensitive analog grounding, and compatibility with Long/Short Frame Sync PCM timing formats.

Technical Context

The MC145483DW implements a fully-differential analog signal path: input op amp (TI+/TI–) drives a differential switched-capacitor band-pass filter (200–3400 Hz), followed by a 13-bit linear successive-approximation ADC. The DAC section reconstructs 2's complement data via a differential 13-bit DAC, sinX/X-compensated 3400 Hz low-pass filter, and active R-C post-filter.

Digital interface flexibility includes support for multiple master clock frequencies (256 kHz to 4.096 MHz), frame sync independence (FST/FSR asynchronous operation), and three operational modes: standard 13-bit transfer, sign-bit extended (16-bit), and receive gain-adjust (16-bit with 3-bit attenuation control). Power-down is achieved via PDI pin or dual-frame-sync hold.

Key Specifications

Pinout & Package

MC145483DW is housed in a 20-pin SOG (Small Outline Gull-wing) package per Case 751D, with 0.65 mm lead pitch and gull-wing surface-mount leads. Pin layout supports compact PCB placement and robust analog isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PCM codec-filter applications.

Compared with MC145483DW, MC145504DW trades resolution and reference integration for lower cost, while TP3067CP sacrifices linearity and supply flexibility to meet µ-law telephony standards - neither offers the MC145483DW's combination of 13-bit linearity, differential noise immunity, and on-chip 0.886 V reference for –5 dBm0 calibration.

Availability

MC145483DW is available at Aetrix Electronics and suitable for telecom line card interface, DSP-based voice gateway, industrial voice alarm system, and legacy PBX digital trunk interface requiring stable component supply and long-term lifecycle support.

Supply support for MC145483DW 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

Freescale Semiconductor (now part of NXP Semiconductors) is a fabless semiconductor company specializing in mixed-signal and analog-intensive ICs for communications, automotive, and industrial markets.

The MC145483DW belongs to Freescale's voiceband codec-filter product line, engineered specifically for high-fidelity, low-noise digitization and reconstruction of human speech in single-supply telephony systems.

FAQ

What is the primary function of the MC145483DW in a telephony system?

The MC145483DW serves as a complete analog front-end for voiceband digitization and reconstruction. It performs 13-bit linear PCM encoding and decoding, integrates transmit band-pass (200–3400 Hz) and receive low-pass (3400 Hz) filtering, and provides on-chip 0.886 V reference voltage. In a telephony system, the MC145483DW interfaces directly between analog telephone lines or microphones and digital signal processors or TDM buses, eliminating the need for external op amps, filters, or references. Its differential architecture ensures high PSRR and noise immunity critical for clean voice capture.

How does the VAG pin function, and why is it critical for MC145483DW layout?

The VAG pin (Pin 20) outputs a stable mid-supply analog ground (1.5 V) that serves as the reference for all internal analog circuitry in the MC145483DW. It must be decoupled to VSS with a 0.01 µF ceramic capacitor using short, low-inductance traces. This separation prevents digital switching noise on VSS from coupling into sensitive analog nodes. If external audio signals are referenced to VSS instead of VAG, improper routing creates ground loops and degrades SNR. Correct VAG handling is essential to achieve the MC145483DW's specified >75 dB dynamic range and <1 LSB idle noise performance.

Can the MC145483DW operate with asynchronous transmit and receive clocks?

Yes, the MC145483DW supports fully asynchronous operation: FST (transmit frame sync) and FSR (receive frame sync) may run independently at 8 kHz, and BCLKT/BCLKR may use different bit clock frequencies within 256–4096 kHz. This allows flexible integration with mismatched DSPs or framer devices. However, in receive gain-adjust mode (BCLKR = 1), BCLKT must clock both transmit and receive data, and FST/FSR alignment is not required. Asynchronous mode retains full 13-bit linear performance but disables receive gain control and sign-bit extension features.

What are the power-down mechanisms supported by the MC145483DW?

The MC145483DW supports two independent power-down methods: asserting logic low on the PDI pin (Pin 10), or holding both FST and FSR pins low while continuing to clock BCLKT and MCLK. In either case, internal clocks and bias currents halt, and outputs DT, RO–, PO+, PO–, TG, and VAG enter high-impedance states. The VAG Ref pin is pulled to VDD via a high-impedance path. Recovery requires PDI high and valid FST pulses; the MC145483DW remains in reset for at least two FST cycles to ensure proper settling of VAG and analog filters before resuming valid data output.

Does the MC145483DW require external passive components for basic operation?

Yes, the MC145483DW requires external passive components for stable operation: a 0.1 µF ceramic capacitor from VDD to VSS, a 0.01 µF capacitor from VAG to VSS, and a 0.1 µF capacitor from VAG Ref to VSS. For microphone interface, external gain-setting resistors between TI–, TG, and signal source are needed. The PO+/PO– power amplifier also requires external feedback resistors tied to PI. While the MC145483DW integrates all active filters and references, these discrete capacitors and resistors are mandatory for noise suppression, reference stability, and gain control - omitting them degrades SNR, causes oscillation, or prevents calibration compliance.