Semtech Corporation GS1531-CB

Overview

GS1531-CB from Gennum is a multi-rate HD/SD serial digital video serializer with integrated ClockCleaner™ reclocking, SMPTE 292M/259M-C and DVB-ASI compliance, 1.485 Gb/s HD output, 270 Mb/s SD output, and 20-bit/10-bit parallel input support for broadcast-grade video transmission systems.

For engineers reviewing the GS1531-CB datasheet, pinout, applications, or equivalent options, this device serves as a standards-compliant serializer for HD-SDI, SD-SDI, and DVB-ASI interfaces-requiring precise jitter tolerance (≤300 ps input PCLK jitter rejection), programmable loop bandwidth (down to 100 kHz), and configurable data processing including TRS insertion, line number calculation, and EDH packet generation.

Technical Context

The GS1531-CB integrates a PLL-based ClockCleaner™ reclocker with user-adjustable loop bandwidth (via LB_CONT analog voltage) enabling >300 ps input jitter rejection while maintaining SMPTE-spec output jitter. It supports three operational modes-SMPTE (with NRZ→NRZI encoding and scrambling), DVB-ASI (with K28.5 sync insertion and 8b/10b encoding), and Data-Through-with automatic standard detection.

Parallel input accepts 20-bit demultiplexed or 10-bit multiplexed video data at 148.5/74.25/27/13.5 MHz, synchronized to PCLK; serial output drives 75 Ω coaxial cable via dual SDO/SDO differential outputs with auto-slew rate selection (HD/SD) and mute-on-loss-of-clock functionality. Internal flywheel enables TRS timing lock either to embedded TRS signals or external H/V/F timing inputs.

Key Specifications

Pinout & Package

GS1531-CB is housed in an 11 mm × 11 mm Pb-free QFN-84 package with exposed thermal pad (package code CB per Gennum ordering info). Pin assignments follow the documented 10×9 grid layout with dedicated power domains (CORE_VDD/CORE_GND, IO_VDD/IO_GND, CD_VDD/CD_GND, CP_VDD/CP_GND, PD_VDD/PD_GND) and functional grouping for parallel data, control, host interface, and serial output.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multi-standard video serializer applications.

Compared with GS1531-CB, GS1532-CB offers extended thermal operation and stronger DVB-ASI error resilience without changing PCB layout, while THS8200IPFP provides lower-cost SDI interfacing but omits critical broadcast features like TRS insertion, EDH, and jitter-tolerant ClockCleaner™ architecture.

Availability

GS1531-CB is available at Aetrix Electronics and suitable for HD-SDI camera interfaces, SD-SDI distribution amplifiers, and DVB-ASI transport encoders requiring stable component supply across broadcast equipment lifecycles.

Supply support for GS1531-CB 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 fabless semiconductor company specializing in high-speed serial interface ICs for professional video, broadcast, and communications markets before its acquisition by Semtech in 2012.

The GS1531-CB belongs to Gennum's HD-LINX® II family of broadcast-qualified serializers, designed specifically for SMPTE and DVB-ASI infrastructure where jitter immunity, metadata insertion, and multi-standard flexibility are mandatory.

FAQ

What video standards does the GS1531-CB support natively?

The GS1531-CB natively supports SMPTE 292M (HD-SDI), SMPTE 259M-C (SD-SDI), and DVB-ASI standards through dedicated encoding paths. In SMPTE mode, it performs NRZ→NRZI conversion and scrambling; in DVB-ASI mode, it inserts K28.5 sync characters and applies 8b/10b encoding. The GS1531-CB detects input standard automatically and configures its internal pipeline without host intervention.

How does the ClockCleaner™ function reduce jitter in the GS1531-CB?

The GS1531-CB's ClockCleaner™ uses an integrated PLL with user-adjustable loop bandwidth (as low as 100 kHz via LB_CONT pin) to filter input PCLK jitter. It tolerates >300 ps peak-to-peak jitter on PCLK while delivering serial output jitter within SMPTE 292M limits (<125 ps typical). This allows the GS1531-CB to regenerate clean serial streams from noisy or long-trace parallel clocks - a key requirement in broadcast camera and router designs.

Can the GS1531-CB insert TRS, EDH, and line numbers into the serial output stream?

Yes - when IOPROC_EN/DIS is asserted HIGH, the GS1531-CB can insert TRS (timing reference signals), EDH (error detection and handling) packets, SMPTE 352M payload identifiers, line numbers, CRC checksums, and ANC data checksums. These functions are enabled/disabled individually via host interface registers or globally via control pins. The GS1531-CB also supports illegal code remapping and blanking control for full broadcast compliance.

What is the role of the RSET pin on the GS1531-CB?

The RSET pin on the GS1531-CB sets the amplitude of the serial digital output (SDO/SDO) by controlling the cable driver's current source. Connecting a 281 Ω ±1% resistor from RSET to CD_VDD configures the GS1531-CB for 800 mV_p-p output into a 75 Ω load - meeting SMPTE 292M/259M-C amplitude specifications. Adjusting RSET allows fine-tuning of output swing for different cable lengths or termination conditions.

Does the GS1531-CB require an external VCO, and if so, which one is recommended?

Yes - the GS1531-CB requires an external VCO for its PLL, with Gennum specifying the GO1555 (preferred for new designs) or GO1525. The GS1531-CB provides dedicated VCO_VCC, VCO_GND, and differential VCO inputs, and generates the control voltage (LF) and charge pump supplies (CP_VDD/CP_GND) to drive the external oscillator. The GO1555 delivers the 1.485 GHz fundamental frequency needed for HD-SDI operation.