NXP Semiconductors MC145481SD

Overview

MC145481SD from Freescale Semiconductor is a single-supply, 20-pin SSOP PCM codec-filter IC performing voice digitization and reconstruction with pin-selectable μ-Law or A-Law companding, on-chip 200 Hz–3.4 kHz band-pass and smoothing filters, and integrated 0.886 V precision reference voltage - used in telephony line interface circuits requiring low-noise analog processing and 8 kHz sampling compliance.

For engineers reviewing the MC145481SD datasheet, MC145481SD pinout, MC145481SD application, or MC145481SD equivalent, this page delivers verified technical context, differential analog architecture details, clock interface mode support (IDL/GCI/Long/Short Frame Sync), power-down behavior, and real-world telecommunication system integration guidance.

Technical Context

The MC145481SD implements a fully-differential analog signal path from TI+/TI– through active R-C pre-filtering, differential switched-capacitor band-pass (200 Hz–3.4 kHz) and high-pass filtering, and differential compressing ADC - enabling 42 dB dynamic range with 30 dB SNR at –5 dBm TLP. Its autozeroed bandgap reference and shared CDAC/RDAC architecture ensure temperature- and supply-independent companding accuracy.

Digital interface supports four timing modes (Long Frame Sync, Short Frame Sync, IDL, GCI) via FST/FSR/BCLKT/BCLKR pin configuration; MCLK accepts 256 kHz–4.096 MHz with automatic prescaling to generate internal 256 kHz sequencing clock; power-down is triggered either by PDI = 0 or simultaneous FST = FSR = 0 for ≥2 frames.

Key Specifications

Pinout & Package

MC145481SD is housed in a 20-pin SSOP package (Case 940C), 0.65 mm pitch, 7.2 mm × 5.3 mm body size, with exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC145503DW, MC145481SD integrates the VAG reference and reduces external component count; compared with CS5321-KP, it delivers drop-in G.711 compliance with minimal external circuitry but trades off resolution for telephony-optimized performance and power efficiency.

Availability

MC145481SD is available at Aetrix Electronics and suitable for telephony line cards, ISDN terminal adapters, VoIP FXS ports, and digital PBX voice modules requiring stable component supply, long-lifecycle support, and G.711-compliant analog interface performance.

Supply support for MC145481SD 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 automotive, industrial, and communications ICs with emphasis on mixed-signal and RF solutions.

The MC145481SD belongs to Freescale's telecommunication codec family designed specifically for voice digitization in PSTN, ISDN, and VoIP infrastructure - prioritizing G.711 compliance, low power, and system-level integration over general-purpose audio fidelity.

FAQ

What is the primary function of the MC145481SD in a telephony system?

The MC145481SD performs end-to-end PCM voice digitization and reconstruction with integrated anti-aliasing and smoothing filters, μ-Law or A-Law companding, and calibrated –5 dBm TLP output. In telephony systems, MC145481SD replaces discrete op-amps, filters, and reference circuits - serving as the core analog front-end for line cards, FXS ports, and ISDN interfaces compliant with ITU-T G.711.

How does the MC145481SD handle power-down, and what happens to its analog outputs?

The MC145481SD supports two power-down methods: asserting PDI = 0 or holding both FST and FSR low for ≥2 frames. During power-down, RO–, PO+, PO–, TG, DT, and VAG enter high-impedance states; VAG Ref is pulled to VDD via high-impedance circuitry. MC145481SD resumes normal operation within two FST cycles after PDI returns high and valid frame sync is restored - ensuring glitch-free reactivation in burst-mode telephony systems.

Can the MC145481SD operate with a 3.3 V supply, and what is its typical power consumption at that voltage?

Yes, MC145481SD operates across 2.7 V to 5.25 V, including standard 3.3 V supplies. At 3 V, its typical power dissipation is 8 mW in active mode and drops to 0.01 mW in power-down mode. This low active power enables dense deployment in multi-channel line cards without thermal derating, while the ultra-low standby draw supports energy-efficient always-on telephony gateways.

What clock frequencies are supported on the MCLK pin of the MC145481SD, and how is internal timing derived?

The MC145481SD MCLK pin accepts 256 kHz, 512 kHz, 1.536 MHz, 1.544 MHz, 2.048 MHz, 2.56 MHz, or 4.096 MHz. An internal prescaler automatically selects the correct divide ratio to generate the required 256 kHz internal sequencing clock for ADC/DAC and filter operation. MC145481SD does not require external clock dividers - simplifying system clock tree design while maintaining strict 8 kHz frame alignment regardless of MCLK frequency.

Does the MC145481SD require external analog filters, or are filtering functions fully integrated?

All critical analog filtering is fully integrated in MC145481SD: a 2-pole Butterworth active R-C pre-filter, 5-pole switched-capacitor band-pass (200 Hz–3.4 kHz), 3-pole switched-capacitor high-pass (200 Hz cutoff), and 2-pole active R-C post-filter. No external analog filters are needed for G.711 compliance - only decoupling capacitors (0.1 µF on VDD/VAG Ref, 0.01 µF on VAG) and external gain-setting resistors for TI–/PI are required for basic operation.