NXP Semiconductors MC145481SDR2

Overview

MC145481SDR2 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 bandpass filtering, and integrated 0.886 V precision reference voltage; used in telephony line interface cards, ISDN terminal adapters, and digital PBX voice channel modules.

For engineers reviewing the MC145481SDR2 datasheet, MC145481SDR2 pinout, MC145481SDR2 application, or MC145481SDR2 equivalent, this device supports synchronous/asynchronous operation across IDL, GCI, Long/Short Frame Sync modes, delivers 8 mW typical power dissipation at 3 V, and integrates differential switched-capacitor filters for noise-immune analog signal processing.

Technical Context

The MC145481SDR2 implements a fully differential analog signal path: transmit input passes through an active R-C pre-filter, single-ended-to-differential converter, 5-pole switched-capacitor low-pass (3.4 kHz), and 3-pole high-pass (~200 Hz) before μ/A-law compressing ADC conversion. Receive path uses differential D/A, sinX/X-compensated 3.4 kHz low-pass filter, and active R-C post-filtering.

Digital interface supports four timing modes-Long Frame Sync, Short Frame Sync, IDL (BCLKR = 1), and GCI (BCLKR = 0)-with automatic MCLK prescaling for 256 kHz–4.096 MHz inputs; power-down is achieved via PDI pin or simultaneous FST/FSR low assertion, placing RO−, PO+, PO−, DT, TG, and VAG in high-impedance state.

Key Specifications

Pinout & Package

MC145481SDR2 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. Pin functions are validated per Freescale MC145481 datasheet Rev 2 (TN98111300).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC145572DW and TP3067CP, the MC145481SDR2 uniquely combines pin-selectable μ/A-law, 2.7–5.25 V operation, SSOP packaging, and fully integrated analog filtering - making it the only option supporting global telephony standards in space-constrained, low-power line cards.

Availability

MC145481SDR2 is available at Aetrix Electronics and suitable for telephony line interface cards, ISDN terminal adapters, and digital PBX voice channel modules requiring stable component supply, long-lifecycle sourcing, and traceable manufacturing origin.

Supply support for MC145481SDR2 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 embedded processing, analog, and mixed-signal solutions for automotive, industrial, and communications markets.

The MC145481SDR2 belongs to Freescale's telecommunication interface product line, designed specifically for voice digitization in PSTN, ISDN, and digital PBX infrastructure where low-power, high-fidelity, and multi-standard compliance are critical.

FAQ

What is the operating voltage range for the MC145481SDR2?

The MC145481SDR2 operates from a single 2.7 V to 5.25 V supply. This wide range allows direct use in both modern 3 V telecom systems and legacy 5 V designs without level-shifting circuitry. The internal reference and analog circuitry maintain specified performance across this entire range, as verified in Freescale's TN98111300 datasheet Rev 2.

How does the MC145481SDR2 handle μ-law versus A-law companding selection?

The MC145481SDR2 uses the Mu/A pin (Pin 16) for hardware-selectable companding: connecting it to VDD enables μ-law, while connecting it to VSS enables A-law. This selection configures both the encoder's compression curve and the decoder's expansion algorithm identically, ensuring end-to-end consistency without software intervention. The MC145481SDR2 does not support dynamic switching during operation.

Can the MC145481SDR2 operate in power-down mode, and how is it activated?

Yes, the MC145481SDR2 supports two power-down methods: asserting logic low on the PDI pin (Pin 10), or holding both FST and FSR pins low while maintaining MCLK and BCLKT clocks. In either case, analog outputs (RO−, PO+, PO−, TG), digital output (DT), and VAG enter high-impedance state, reducing power dissipation to 0.01 mW. Recovery requires PDI high and valid FST pulses.

What digital interface modes does the MC145481SDR2 support, and how are they selected?

The MC145481SDR2 supports Long Frame Sync, Short Frame Sync, IDL (BCLKR = 1), and GCI (BCLKR = 0) modes. Mode detection is automatic based on FST pulse width and BCLKR logic state - no register programming required. All modes use the same pinout and timing parameters, enabling flexible system-level clock architecture without hardware redesign.

Does the MC145481SDR2 include integrated filtering, and what are its characteristics?

Yes, the MC145481SDR2 integrates transmit bandpass filtering (200 Hz–3.4 kHz) and receive low-pass filtering (3.4 kHz cutoff with sinX/X compensation). These are implemented as differential switched-capacitor filters, eliminating external passive components. The transmit path also includes active R-C pre-filtering; the receive path adds active R-C post-filtering to suppress switched-capacitor residue.