NXP Semiconductors MC145484EN

Overview

MC145484EN from Freescale Semiconductor is a 5 V single-supply 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 (Tx) and 3.4 kHz low-pass (Rx) filters, and integrated precision 1.575 V reference for –0 dBm TLP @ 600 Ω. It serves as the analog front-end in telephony line interface circuits, especially electronic SLIC interfaces.

For engineers reviewing the MC145484EN datasheet, MC145484EN pinout, MC145484EN application, or MC145484EN equivalent, key selection considerations include its differential analog signal path, 8-bit companded PCM I/O, support for Long/Short Frame Sync, IDL, and GCI timing modes, and push-pull 300 Ω power drivers with external gain adjustment.

Technical Context

The MC145484EN implements a fully-differential analog signal chain: transmit path includes active R-C pre-filtering, single-ended-to-differential conversion, 5-pole switched-capacitor band-pass (200 Hz–3.4 kHz), and autozeroed successive-approximation ADC; receive path uses differential DAC, sinX/X-compensated 5-pole switched-capacitor low-pass filter, active R-C post-filtering, and buffered RO– output.

Digital interface supports four timing 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 and independent FST/FSR frame sync handling. Power-down is achieved via PDI pin or dual-frame-sync hold, placing TG, RO–, PO+, PO–, DT, and VAG in high-impedance state.

Key Specifications

Pinout & Package

MC145484EN is packaged in 20-pin SOG (Case 751D), SSOP (Case 940C), or TSSOP (Case 948E). The EN suffix denotes SOG package per Freescale ordering nomenclature (MC145484DW = SOG).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC145484EN, MC145484DW offers identical functionality in a through-hole-compatible SOG package ideal for prototyping and repair, while MC145484SD delivers the same performance in a space-saving SSOP variant-both preserve full pin compatibility, timing behavior, and μ-law/A-law selection logic.

Availability

MC145484EN is available at Aetrix Electronics and suitable for electronic SLIC interfaces, digital line cards, ISDN terminal adapters, and VoIP gateway analog front-ends requiring stable component supply and long-term obsolescence management.

Supply support for MC145484EN 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 strong legacy in telephony and analog mixed-signal design.

The MC145484EN belongs to Freescale's telecommunication codec family, engineered specifically for voice digitization in PSTN infrastructure, SLIC interfacing, and ISDN terminal equipment-prioritizing low power, high PSRR, and multi-standard timing flexibility.

FAQ

What is the function of the VAG pin on the MC145484EN?

The VAG pin on the MC145484EN provides a mid-supply (2.5 V) analog ground reference for all internal analog circuitry. It is generated by an on-chip precision voltage reference and must be decoupled to VSS with a 0.01 µF ceramic capacitor. When the MC145484EN is in power-down mode, the VAG pin becomes high-impedance, isolating analog bias from the rest of the system.

Does the MC145484EN support both μ-law and A-law companding simultaneously?

No, the MC145484EN supports only one companding law at a time, selected by the logic level on the Mu/A pin (Pin 16): high for μ-law, low for A-law. This hardware-selectable configuration ensures deterministic behavior without software intervention, and the MC145484EN does not perform dynamic switching between laws during operation.

Can the MC145484EN operate with asynchronous frame sync signals on FST and FSR?

Yes, the MC145484EN supports asynchronous FST and FSR in Long Frame Sync and Short Frame Sync modes, as confirmed in the functional description. However, in IDL and GCI modes (enabled by BCLKR logic level), FST and FSR are used for channel selection rather than independent timing, and synchronization is derived from the common BCLKT clock.

What is the maximum load the PO+/PO– outputs of the MC145484EN can drive?

The PO+/PO– outputs of the MC145484EN are rated to drive a 300 Ω resistive load to ±3.15 V peak (6.3 Vpp) with specified distortion. They can also drive a 100 Ω resistive load or a 100 nF piezoelectric transducer in series with a 20 Ω resistor, albeit with increased distortion. For ≥32 Ω loads, PO– gain must be set to 1/4 or less to maintain stability.

How does the MC145484EN achieve power-down, and what pins go high-impedance?

The MC145484EN enters power-down either via the PDI pin (low-active) or by holding both FST and FSR low for several 8 kHz frames. In this state, TG, RO–, PO+, PO–, DT, and VAG become high-impedance; VAG Ref is pulled to VDD; and internal clocks and bias currents are disabled. The MC145484EN consumes only 0.01 mW in this mode.