NXP Semiconductors MC145481ENR2

Overview

MC145481ENR2 from Freescale Semiconductor is a single-supply, 20-pin 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 0.886 V precision reference for –5 dBm TLP at 600 Ω. It targets telephony line interface cards requiring synchronous/asynchronous 8 kHz frame timing and differential analog signal processing.

For engineers reviewing the MC145481ENR2 datasheet, MC145481ENR2 pinout, MC145481ENR2 application, or MC145481ENR2 equivalent, key selection criteria include its fully-differential analog architecture, 300 Ω push-pull power drivers with external gain adjust, 2.7–5.25 V supply operation, 8 mW typical power dissipation at 3 V, and compatibility with IDL/GCI/Short/Long Frame Sync digital interfaces.

Technical Context

The MC145481ENR2 implements a differential switched-capacitor architecture: transmit path uses active R-C pre-filtering → differential converter → 5-pole 3.4 kHz low-pass → 5-pole 200 Hz high-pass → differential compressing ADC; receive path applies differential DAC → sinX/X-compensated 3.4 kHz low-pass → active R-C post-filtering → RO– output buffer. All analog signal processing is differential, enabling 2× input amplitude headroom and common-mode power supply noise rejection.

Digital interface supports four timing modes (Long Frame Sync, Short Frame Sync, IDL, GCI) selected via BCLKR and FSR pins; MCLK accepts 256 kHz–4.096 MHz with automatic prescaling to generate internal 256 kHz sequencing clock; Mu/A pin selects companding law; PDI enables 0.01 mW power-down mode with high-impedance outputs including VAG, TG, RO–, PO+, PO–, and DT.

Key Specifications

Pinout & Package

MC145481ENR2 is packaged in 20-pin SSOP (Case 940C), with lead pitch of 0.65 mm and body dimensions 7.2 mm × 5.3 mm. Pin functions are validated per Freescale Semiconductor Technical Data MC145481/D (Rev 2, Nov 1998).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC145481ENR2, MC145503DW simplifies layout by removing VAG Ref but sacrifices analog ground noise isolation, while TP3054CP demands external reference and dual supplies, increasing system cost and calibration effort - MC145481ENR2 remains optimal for single-supply, SSOP-based telecom line cards needing guaranteed –5 dBm TLP accuracy.

Availability

MC145481ENR2 is available at Aetrix Electronics and suitable for central office line cards, digital PBX interfaces, DSLAM voice ports, and VoIP gateway FXS modules requiring stable component supply across extended product lifecycles.

Supply support for MC145481ENR2 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) was a leading designer of analog and mixed-signal ICs for telecommunications infrastructure, automotive, and industrial markets.

The MC145481ENR2 belongs to Freescale's legacy telecom codec-filter product line, engineered specifically for voice digitization in PSTN, ISDN, and early VoIP access equipment with emphasis on integration, low power, and global companding compliance.

FAQ

What is the operating voltage range for the MC145481ENR2?

The MC145481ENR2 operates from a single 2.7 V to 5.25 V supply. This wide range allows direct use with both 3 V and 5 V system rails without external regulators. At 3 V, typical power dissipation is 8 mW; at 5.25 V, it remains within safe thermal limits for SSOP packaging. The device maintains full specification compliance across this entire range, including reference voltage accuracy and filter cutoff stability.

How does the MC145481ENR2 handle power-down functionality?

The MC145481ENR2 supports two power-down methods: asserting logic-low on PDI (Pin 10), or holding both FST and FSR low while clocking MCLK and BCLKT. In either case, RO–, PO+, PO–, TG, DT, and VAG enter high-impedance states, and VAG Ref is pulled to VDD. The device consumes only 0.01 mW in this mode. Recovery requires PDI high and valid FST pulses; DT remains high-impedance for ≥2 FST cycles to prevent bus contention.

Which digital interface modes does the MC145481ENR2 support?

The MC145481ENR2 supports four industry-standard PCM timing modes: Long Frame Sync, Short Frame Sync, IDL (BCLKR = 1), and GCI (BCLKR = 0). Mode selection is determined by BCLKR logic level and FSR state. All modes operate with 8 kHz frame sync and support bit clock frequencies from 64 kHz to 4.096 MHz. Timing diagrams for each mode are documented in Freescale's MC145481/D datasheet Figure 2.

What is the purpose of the VAG and VAG Ref pins on the MC145481ENR2?

VAG (Pin 20) provides a mid-supply analog ground reference (VDD/2) for all internal analog circuitry; it must be decoupled to VSS with 0.01 µF. VAG Ref (Pin 1) bypasses the on-chip VAG generation circuitry and requires a 0.1 µF capacitor to VSS. Together, they isolate analog ground from digital noise - critical when external analog signals are referenced to VSS. In power-down mode, VAG becomes high-impedance and VAG Ref is pulled to VDD.

Can the MC145481ENR2 drive a 600 Ω telephone line directly?

No - the MC145481ENR2's PO+/PO– outputs are optimized for 300 Ω loads (±1.772 V peak, +7 dBm), matching SLIC or hybrid transformer inputs. Driving 600 Ω directly would reduce output level by 6 dB and risk distortion. For 600 Ω line termination, an external line driver (e.g., MC3419 SLIC) or impedance-matching transformer is required. The MC145481ENR2 is designed as a codec-filter front-end, not a full line driver.