Semtech Corporation GB4571-CKAE3

Overview

GB4571-CKAE3 from Gennum Corporation is a precision video buffer IC with strobed DC restore functionality, designed for accurate back porch clamping in analog video signal chains. It operates from ±4.5 V to ±13.2 V supplies, delivers ±0.1 dB flatness to 80 MHz, achieves ±1 mV clamping accuracy, and supports NTSC/PAL/SECAM/RGB signals in broadcast-grade video equipment.

For engineers reviewing the GB4571-CKAE3 datasheet, pinout, applications, or equivalent options, key selection criteria include clamping distortion (±1 mV), recovery time (190–600 µs for 0.1 V offset), differential phase (≤0.05°), supply voltage range, and SOIC-8 Pb-free packaging compatibility with production switchers and linear keyers.

Technical Context

The GB4571-CKAE3 implements a strobed operational transconductance amplifier (OTA) architecture with a 600 kHz low-pass filtered differential input to reject color burst and high-frequency noise during clamping. Its non-linear V-to-I feedback converter enables faster recovery from large DC offsets while preserving loop stability during steady-state operation.

Clamping occurs only when the STROBE input is low, integrating over the full back porch period to minimize noise sensitivity-unlike sample-and-hold methods. The CHOLD capacitor (pin 1) stores the corrective voltage, and internal Darlington emitter-follower output ensures ±0.1 dB bandwidth to 80 MHz with optimal 18 pF load capacitance.

Key Specifications

Pinout & Package

GB4571-CKAE3 is housed in an 8-pin SOIC package (JEDEC MS-012, 3.9 mm width), RoHS-compliant and Pb-free per ordering suffix E3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar video DC restoration applications.

Compared with EL4571CN and LMH6732MA, GB4571-CKAE3 provides integrated strobe-controlled DC restoration in a single SOIC-8 package with wider supply range, higher bandwidth, and guaranteed ±1 mV accuracy - reducing design risk and board area in broadcast infrastructure.

Availability

GB4571-CKAE3 is available at Aetrix Electronics and suitable for NTSC/PAL broadcast processing, multimedia graphics overlay, and production switchers requiring stable component supply with Pb-free compliance and industrial temperature range (0°C to 70°C).

Supply support for GB4571-CKAE3 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

Gennum Corporation was a Canadian semiconductor company specializing in high-performance analog and mixed-signal ICs for video, communications, and timing applications before its acquisition by Microchip Technology in 2011.

The GB4571 product line was engineered specifically for precision analog video signal conditioning-targeting broadcast infrastructure where DC level stability, differential gain/phase performance, and clamping accuracy directly impact picture quality.

FAQ

What is the recommended value for the CHOLD capacitor on GB4571-CKAE3?

The CHOLD capacitor (pin 1) must be selected to maintain closed-loop stability. Per the datasheet, the ratio CIN:CHOLD should be approximately 20,000:1. With typical CIN ≈ 2 pF, CHOLD should be ~40 nF. Larger values improve low-frequency stability but increase recovery time; smaller values reduce recovery time but risk oscillation. Always verify stability with actual video waveforms and scope measurements on GB4571-CKAE3.

Does GB4571-CKAE3 support SECAM video signals?

Yes, GB4571-CKAE3 explicitly supports SECAM video signals, as confirmed in the Applications section of the datasheet alongside NTSC, PAL, and RGB. Its wide bandwidth (80 MHz), low differential phase (≤0.05°), and ±1 mV clamping accuracy ensure faithful DC restoration across all major analog broadcast standards-including SECAM's dual FM subcarriers-without requiring configuration changes.

Can GB4571-CKAE3 operate from a single supply?

No, GB4571-CKAE3 requires dual symmetric supplies (±VS) ranging from ±4.5 V to ±13.2 V. Its internal architecture-including Darlington output stage and strobed OTA-depends on true bipolar rails. Single-supply operation is not supported, and attempting it will result in undefined behavior or device damage. For single-supply designs, external level-shifting circuitry or alternative ICs must be used instead of GB4571-CKAE3.

What is the minimum STROBE pulse width required for reliable clamping on GB4571-CKAE3?

The minimum active-low STROBE pulse width for GB4571-CKAE3 is 2.0 µs, as specified in the Electrical Characteristics table under "Strobe Pulse Width (tPWL)." Pulses shorter than this may fail to fully integrate the back porch period, resulting in reduced clamping accuracy or instability. For robust operation in broadcast systems, use ≥2.5 µs pulses aligned to the horizontal back porch, as validated in the typical application circuit with GS4881 sync separator.

How does GB4571-CKAE3 achieve faster recovery from DC offset changes compared to sample-and-hold clamps?

GB4571-CKAE3 uses a non-linear V-to-I converter in its feedback path: larger VIN–VCLAMP differences drive proportionally larger corrective currents into the CHOLD capacitor, accelerating recovery from large offsets. In contrast, sample-and-hold clamps apply fixed corrections regardless of error magnitude. This adaptive response-combined with full back porch integration-gives GB4571-CKAE3 recovery times of 190–600 µs (0.1 V offset), significantly faster than conventional methods while maintaining stability.