Texas Instruments UCC3750N

Overview

UCC3750N from Texas Instruments is a dedicated source ringer controller IC for four-quadrant flyback-based telephone ring generators. It integrates a programmable sine-wave reference (20/25/50 Hz), dual synchronous rectifier drivers (GD2/GD3), primary-side PWM driver (GD1), charge-pump gate drive voltage generation (VCP ≥11 V), and DC current limiting with ±0.5 V threshold. It operates from a single 5 V supply and targets telecom line card applications requiring isolated AC+DC ringing signals.

For engineers reviewing the UCC3750N datasheet, UCC3750N pinout, UCC3750N application, or UCC3750N equivalent, this page delivers verified technical context, exact pin functions, real-world ringing topology integration, and validated alternative options - all grounded in TI's SLUS172C datasheet and DW/N package documentation.

Technical Context

The UCC3750N implements mode-aware PWM control using separate magnitude (MAG) and polarity (SIGN) paths derived from its error amplifier output, enabling stable four-quadrant operation across all power flow directions. Its internal 32 kHz crystal-locked sine generator feeds programmable frequency selection (FS0/FS1) and provides low-THD (≤2%) reference output centered at 3 V with ±0.15 V offset tolerance.

Control logic decodes operating mode (1–4) based on reference polarity and power flow direction, routing PWM to GD1 (mode 1/3), GD2 (mode 4), or GD3 (mode 2) while synchronizing rectifier switching via clock-derived signals. The charge pump (VS1/VS2/VCP) delivers ≥11 V gate drive from 5 V VDD, supporting high-side p-channel and low-side n-channel MOSFETs in isolated secondary-side placement.

Key Specifications

Pinout & Package

Dual-in-line (DIL-28) and SOIC-28 (DW/N) packages - 28-pin through-hole or surface-mount; pin-compatible with UCC2750 series; RoHS-compliant NIPDAU finish; MSL Level-2-260°C-1 year.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar source ringer controller applications.

Compared with UCC2750DW, the UCC3750N offers lower-cost commercial-temperature operation and identical feature set for indoor line cards; versus MAX14951, it provides full four-quadrant programmability and external MOSFET control at the cost of higher component count and layout complexity.

Availability

UCC3750N is available at Aetrix Electronics and suitable for telephone line card design, central office interface development, and legacy PBX retrofit projects requiring stable component supply and long-term manufacturability.

Supply support for UCC3750N 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies with over 50 years of innovation in industrial and communications ICs.

The UCC3750N belongs to TI's telecommunication power controller product line, designed specifically to replace discrete ringing solutions in analog telephone interface circuits with integrated, reliable, and standards-compliant ICs.

FAQ

What is the maximum allowable voltage on the VCP pin of the UCC3750N?

The absolute maximum forced voltage on the VCP pin of the UCC3750N is 13.2 V. Operating above this level risks permanent damage to the internal charge-pump circuitry. In normal operation, VCP delivers 11–14 V (at 10 mA load) when powered from 5 V VDD; external regulation must be clamped below 13.2 V. Always verify VCP ripple remains <500 mV peak-to-peak under full load to ensure stable gate drive.

Can the UCC3750N generate frequencies other than 20 Hz, 25 Hz, and 50 Hz?

Yes - the UCC3750N supports custom frequencies by replacing the 32 kHz crystal with another value (e.g., 16 kHz yields 10/12.5/25 Hz) or by driving XTAL1 with an external clock signal at a fixed multiple (e.g., 32 kHz × 640 = 20.48 MHz yields 32 kHz output). When FS0 and FS1 are both high, SINREF accepts external sine input, enabling arbitrary frequency injection with matching 3 V DC offset.

How does the UCC3750N implement four-quadrant operation without instability at zero-crossings?

The UCC3750N avoids instability by splitting the error amplifier output into magnitude (MAG) and polarity (SIGN) signals. MAG drives the PWM comparator against the oscillator ramp, while SIGN - combined with reference polarity - selects the correct output driver (GD1/GD2/GD3) and inverts feedback phase for modes 2 and 3. This hardware-decoupled approach ensures consistent loop gain polarity across all four quadrants, eliminating zero-crossing oscillation.

What is the purpose of the SWRLY pin on the UCC3750N?

The SWRLY pin on the UCC3750N outputs a logic signal that leads battery offset zero-crossings by ~5 ms, enabling zero-voltage switching of mechanical relays in telephone line interfaces. It sources up to 250 µA and is synchronized to the internal sine reference - critical for minimizing relay arcing, contact wear, and audible click noise in POTS line cards.

Is the UCC3750N compatible with both p-channel and n-channel secondary-side MOSFETs?

Yes - the UCC3750N supports both: GD2 provides logically inverted output optimized for p-channel synchronous rectifiers (e.g., IRF840), while GD3 delivers non-inverted drive for n-channel devices (e.g., MTP2P50E). The IC's isolated secondary-side placement and VCP-supplied gate drive eliminate level-shifting requirements, allowing direct connection to either FET type without external circuitry.