NXP Semiconductors MC44BC375UEF

Overview

MC44BC375UEF from Freescale Semiconductor is a PLL-tuned VHF audio/video high-integration modulator IC designed for channel 3/4 broadcast modulation in consumer video equipment. It integrates VHF carrier synthesis, on-chip 4.5/5.5 MHz sound subcarrier generation, programmable picture-to-sound ratio (14 dB or 16 dB), peak white clipping, and logic output port control - all in a single SO16NB package with no external varicaps or tank circuits required.

For engineers reviewing the MC44BC375UEF datasheet, MC44BC375UEF pinout, MC44BC375UEF application, or MC44BC375UEF equivalent, this page delivers verified technical context, exact pin functions, real-world modulation performance metrics (e.g., 76 dBµV RF output, <1% FM distortion), and validated alternatives for VCR, set-top box, and analog video modulator designs.

Technical Context

The MC44BC375UEF implements a dual-loop PLL architecture: a UHF oscillator (divided to VHF) locked to a 4 MHz crystal reference (31.25 kHz after /128 division), and a separate sound PLL generating 4.5 MHz or 5.5 MHz subcarriers. Channel selection (CH3/CH4) is controlled by the CHS pin, while PSS and SFS pins configure picture-to-sound ratio and sound frequency respectively.

Its modulator section accepts composite video (1 V_p-p, negative sync) and audio inputs, applies pre-emphasis (75 µs or 50 µs), performs FM audio and AM video modulation, and outputs a 75 Ω RF signal with transient inhibit during PLL lock-up (263 ms delay). The LOP pin provides open-collector switching (≤15 mA) for antenna control in power-save mode.

Key Specifications

Pinout & Package

MC44BC375UEF is housed in a 16-pin SOIC narrow-body (SO16NB) package per Freescale specification, with 1.27 mm pitch, 10.0 mm × 6.2 mm body size, and exposed pad not present. Pin 1 is marked by a dot/dimple adjacent to sprocket holes on tape-and-reel packaging.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar VHF audio/video modulator applications.

Compared with MC44BC374UEF and SA606DK, the MC44BC375UEF uniquely integrates full VHF modulator functionality - including PLL, sound oscillator, video clamp, peak clip, and RF output - reducing component count by >80% and eliminating factory alignment.

Availability

MC44BC375UEF is available at Aetrix Electronics and suitable for VCRs, set-top boxes, portable media players, and security camera transmitters requiring stable component supply and long-lifecycle support for legacy analog video interfaces.

Supply support for MC44BC375UEF 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 consumer electronics, automotive, and industrial markets.

The MC44BC375UEF belongs to Freescale's broadcast modulator product line, engineered specifically for cost-sensitive, high-volume analog video equipment requiring fully integrated, drop-in RF modulation with zero external tuning.

FAQ

What is the function of the PSave/LO pin on the MC44BC375UEF?

The PSave/LO pin on the MC44BC375UEF controls both power-save mode and the Logic Output Port (LOP). When driven LOW, it disables internal VCOs, mixers, and modulators-reducing supply current to 5 mA-and simultaneously forces the LOP pin to low voltage for antenna switching. In HIGH state, the device operates normally with full modulation capability. This dual-function pin simplifies system-level power sequencing and peripheral control without external logic.

Does the MC44BC375UEF require external components for crystal oscillator operation?

No, the MC44BC375UEF does not require external load capacitors or biasing components for its 4 MHz crystal oscillator. The internal oscillator circuit provides sufficient negative resistance (>1 kΩ) and built-in feedback to drive standard fundamental-mode crystals directly on the XTAL pin. Only a 4 MHz crystal is needed; no external capacitors, resistors, or inductors are required for basic operation.

How does the MC44BC375UEF handle video input signal levels and synchronization?

The MC44BC375UEF accepts a 1 V_p-p composite video input with negative-going sync pulses. It internally clamps the sync tip to establish DC reference and applies peak-white clipping to prevent overmodulation. The video input impedance is 500 kΩ, and the modulation depth is 85% at nominal input-adjustable downward via external resistive dividers. No external sync separator or clamping circuitry is needed.

Can the MC44BC375UEF be used for both NTSC and PAL video standards?

The MC44BC375UEF supports NTSC M/N (5.5 MHz sound, 14/16 dB picture-to-sound ratio) and NTSC J (4.5 MHz sound) via SFS and PSS pin configuration, but it is not designed for PAL standards. Its video bandwidth (−0.5 dB at 5 MHz), differential phase (±1°), and chroma performance align with NTSC specifications. For PAL applications, external filtering or alternate ICs meeting 4.43 MHz chroma and 5.5 MHz sound requirements would be necessary.

What is the purpose of the transient output inhibit feature in the MC44BC375UEF?

The transient output inhibit feature in the MC44BC375UEF disables video and sound modulation for 263 ms after power-on or exit from standby mode. This prevents spurious RF emissions during UHF PLL lock acquisition, ensuring clean channel switching and compliance with FCC Part 15 radiated emission limits. After the timeout, modulation resumes automatically-no software or external timing circuit is required.