NXP Semiconductors MC145481DW

Overview

MC145481DW from Freescale Semiconductor is a single-supply, 20-pin SOG-packaged PCM codec-filter IC performing voice digitization and reconstruction with pin-selectable μ-Law or A-Law companding. It integrates transmit band-pass (200 Hz–3.4 kHz) and receive low-pass (3.4 kHz) filters, on-chip 0.886 V precision reference, and fully differential analog signal path. It serves in telephony line interface circuits requiring 8 kHz sampling and 300 Ω line driver capability.

For engineers reviewing the MC145481DW datasheet, MC145481DW pinout, MC145481DW application, or MC145481DW equivalent, key selection criteria include its dual-law companding selectability, 2.7–5.25 V supply range, 8 mW typical power dissipation at 3 V, integrated active R-C pre/post-filtering, and compatibility with IDL/GCI/Long/Short Frame Sync digital interfaces.

Technical Context

The MC145481DW implements a successive-approximation ADC and DAC sharing a differential switched-capacitor architecture with autozeroed bandgap reference. Its analog signal path uses fully differential processing from TI+/TI– through 5-pole transmit band-pass and receive low-pass filters, enabling 2× input amplitude headroom and high PSRR via common-mode noise rejection.

Digital timing supports four modes-Long Frame Sync, Short Frame Sync, IDL (BCLKR = 1), and GCI (BCLKR = 0)-with MCLK auto-scaling across 256 kHz to 4.096 MHz. Power-down is achieved either via PDI pin (logic 0) or by holding both FST and FSR low, placing RO–, PO+, PO–, DT, TG, and VAG in high-impedance state.

Key Specifications

Pinout & Package

MC145481DW is housed in a 20-pin Small Outline Package (SOG), case 751D, with 0.65 mm lead pitch and gull-wing leads. The package is RoHS-compliant and rated for industrial temperature range (–40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC145481DW, MC145503DW sacrifices A-Law support and line driver integration for cost reduction, while TP3054N retains μ/A-law flexibility but mandates 5 V operation and doubles power consumption - making MC145481DW the sole option supporting 2.7–5.25 V, integrated drivers, and dual-law selection in SOG packaging.

Availability

MC145481DW is available at Aetrix Electronics and suitable for telephony line cards, ISDN terminal adapters, DSL customer premises equipment, and VoIP analog telephone adapters requiring stable component supply and long-term industrial lifecycle support.

Supply support for MC145481DW 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 MC145481DW belongs to Freescale's telecommunication codec product line, designed specifically for voice digitization in PSTN, ISDN, and DSL access equipment with emphasis on integration, low power, and global standard compliance.

FAQ

What is the operating voltage range for the MC145481DW?

The MC145481DW operates from a single 2.7 V to 5.25 V supply. This wide range allows direct use with both 3.3 V and 5 V system rails without external regulators. At 3 V, it achieves 8 mW typical power dissipation, and drops to 0.01 mW in power-down mode. The device maintains full specification compliance-including filter response, companding accuracy, and line driver output-across this entire voltage window.

How does the MC145481DW handle μ-Law versus A-Law companding selection?

The MC145481DW selects μ-Law or A-Law companding via the Mu/A pin (Pin 16): logic high (VDD) enables μ-Law per ITU-T G.711 Annex A, and logic low (VSS) enables A-Law per Annex B. This pin must be statically tied during power-up; dynamic switching is not supported. Both schemes use identical 8-bit PCM word structure with sign/chord/step encoding, and the internal DAC and comparator architecture is shared, ensuring matched performance across both laws.

Can the MC145481DW drive a standard 600 Ω telephone line directly?

The MC145481DW does not drive 600 Ω loads directly. Its PO+/PO– outputs are optimized for 300 Ω termination per ITU-T G.732, delivering ±1.772 V (3.544 Vpp) into that load. To interface with legacy 600 Ω lines, an external 2:1 impedance-matching transformer or resistive pad is required. The device's 0.886 V reference is calibrated for –5 dBm into 600 Ω, but output drive capability is specified only for 300 Ω, 100 Ω, or piezoelectric transducers.

What digital interface modes does the MC145481DW support, and how are they configured?

The MC145481DW supports four digital interface modes: Long Frame Sync, Short Frame Sync, IDL (BCLKR = 1), and GCI (BCLKR = 0). Mode selection is determined by BCLKR pin state and frame sync timing. Long/Short Frame Sync are detected automatically based on FST pulse width relative to BCLKT edges; IDL/GCI require static BCLKR assertion. All modes use 8-bit serial PCM data at 8 kHz frame rate, with timing diagrams defined in Freescale document TN98111300.

Is the MC145481DW still in active production, and what is its lifecycle status?

The MC145481DW was originally released by Freescale Semiconductor and is now supported under NXP's legacy product program. While no longer in high-volume production, Aetrix Electronics maintains verified inventory with full traceability and provides extended lifecycle coordination, including last-time-buy planning and obsolescence mitigation for industrial and telecom customers relying on this qualified component.