Texas Instruments UCC2975PW

Overview

UCC2975PW from Texas Instruments is a flyback-topology piezoelectric transformer (PZT) controller IC for CCFL backlight power supplies, operating from 3 V to 13.5 V, featuring programmable voltage-controlled oscillator (VCO), open-lamp protection, dual MOSFET drivers, and 8-pin TSSOP package. It targets narrow-profile LCD enclosures in notebook computers and portable displays.

For engineers reviewing the UCC2975PW datasheet, UCC2975PW pinout, UCC2975PW application, or UCC2975PW equivalent, key selection considerations include its flyback-specific driver configuration (OUTP left open, OUTN active), –40°C to 85°C industrial temperature rating, 95–105 kHz nominal VCO frequency with ROSC/COSC tuning, and dedicated open-lamp fault detection threshold of 1.5 V.

Technical Context

The UCC2975PW implements a resonant flyback topology using a single external switch driven at 50% duty cycle, generating a half-wave rectified sinusoid at the PZT primary. Its VCO uses a precision window comparator (0.7 V–1.7 V thresholds) to regulate lamp current by sweeping frequency from high (strike) to low (operate) across resonance.

Startup preconditioning forces COMP to 0 V for maximum frequency; regulation occurs as the error amplifier slews COMP based on FB feedback (1.5 V reference). Open-lamp detection triggers up to seven retries before entering error shutdown, cleared only by power cycle or OPEN/SD pin reset sequence.

Key Specifications

Pinout & Package

UCC2975PW is housed in an 8-pin TSSOP (PW) package, optimized for low-profile PCB layouts in space-constrained portable displays.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar CCFL PZT controller applications.

Compared with UCC2975PW, UCC3975PW offers identical functionality at lower cost but lacks industrial temperature support, while UCC2976PW shifts topology to half-bridge-enabling higher power density but requiring revised gate drive layout and inductor selection.

Availability

UCC2975PW is available at Aetrix Electronics and suitable for notebook computer backlighting, portable instrument displays, and medical portable monitors requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for UCC2975PW 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 company specializing in analog, embedded processing, and power management technologies with leadership in power conversion ICs.

The UCC2975PW belongs to TI's UCC397x family of piezoelectric transformer controllers, designed specifically for compact, efficient CCFL backlight supplies in portable electronics where low profile and high reliability are critical.

FAQ

What topology does the UCC2975PW support and how is it implemented?

The UCC2975PW supports only the resonant flyback topology. It implements this using OUTN to drive a single external N-channel MOSFET at 50% duty cycle, while OUTP remains unconnected per datasheet specification. This configuration generates a half-wave rectified sinusoid at the piezoelectric transformer primary, enabling compact CCFL power supplies without secondary-side rectification. The UCC2975PW's internal circuitry-including its VCO sweep and open-lamp detection-is optimized exclusively for this flyback use case.

How does the UCC2975PW achieve lamp current regulation?

The UCC2975PW regulates lamp current by controlling the operating frequency of the resonant flyback stage. Lamp current is sensed across RCS, filtered by RFB and CFB, and compared to a 1.5 V internal reference at the FB pin. The resulting error voltage at COMP modulates the VCO frequency-shifting operation rightward on the PZT's gain-vs-frequency curve to increase lamp current or leftward to decrease it. This closed-loop frequency control maintains stable 5 mA lamp current across input voltage and temperature variations.

What is the significance of the 1.5 V open-lamp detection threshold in the UCC2975PW?

The 1.5 V open-lamp detection threshold is a variant-specific parameter for the UCC2975PW (vs. 1.4 V in UCC3975 variants), calibrated to reliably detect CCFL open-circuit faults during startup. When voltage at the OPEN/SD pin exceeds 1.5 V due to missing lamp current, the UCC2975PW initiates up to seven automatic restart attempts. If unsuccessful, it enters error shutdown-preventing uncontrolled voltage rise and protecting both the PZT and display assembly. This threshold ensures compatibility with standard CCFL impedance profiles across the –40°C to +85°C operating range.

Can the UCC2975PW be used with burst-mode dimming, and how is it implemented?

Yes, the UCC2975PW supports burst-mode dimming via the OPEN/SD pin. Applying a pulsed logic signal (low = active, high = off) to OPEN/SD forces the controller into periodic shutdown and restart cycles. During low pulses, the UCC2975PW operates normally; during high pulses, it enters 15 µA shutdown mode, extinguishing the lamp. Duty cycle of the OPEN/SD signal directly controls average lamp brightness. This method avoids audio noise from analog dimming and maintains full PZT gain during each on-cycle, ensuring reliable lamp striking even at lowest brightness levels.

What are the key layout considerations for the OSC pin on the UCC2975PW?

Layout of the OSC pin on the UCC2975PW is critical due to its sensitivity to stray capacitance and noise. External ROSC and COSC must be placed within 2 mm of the OSC pin with short, direct traces; COSC should be an NPO ceramic capacitor (100–1000 pF) with ground plane clearance beneath. Avoid routing digital or switching signals near OSC, and never connect an oscilloscope probe directly during tuning-the added capacitance can shift frequency by >5 kHz. TI recommends verifying final frequency in-system with minimal probing to ensure stable PZT resonance lock.