LMH1983 3G/HD/SD Video Clock Generator with Audio Clock | TI.com

LMH1983 (ACTIVE) 3G/HD/SD Video Clock Generator with Audio Clock


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The LMH1983 is a highly-integrated programmable audio/video (A/V) clock generator intended for broadcast and professional applications. It can replace multiple PLLs and VCXOs used in applications supporting SMPTE serial digital video (SDI) and digital audio AES3/EBU standards. It offers low-jitter reference clocks for any SDI transmitter to meet stringent output jitter specifications without additional clock cleaning circuits.

The LMH1983 features automatic input format detection, simple programming of multiple A/V output formats, genlock or digital free-run modes, and override programmability of various automatic functions. The recognized input formats include HVF syncs for the major video standards, 27 MHz, 10 MHz, and 32/44.1/48/96 kHz audio word clocks.

The dual-stage PLL architecture integrates four PLLs with three on-chip VCOs. The first stage (PLL1) uses an external low-noise 27 MHz VCXO with narrow loop bandwidth to provide a clean reference clock for the next stage. The second stage (PLL2, 3, 4) consists of three parallel VCO PLLs for simultaneous generation of the major digital A/V clock fundamental rates, including 148.5 MHz, 148.5/1.001 MHz, and 98.304 MHz (4 × 24.576 MHz). Each PLL can generate a clock and a timing pulse to indicate top of frame (TOF).

When locked to reference, an internal 10-bit ADC will track the loop filter control voltage. When a loss of reference (LOR) occurs, the LMH1983 can be programmed to hold the control voltage to maintain output accuracy within ±0.5 ppm (typical) of the previous reference. The LMH1983 can be configured to re-synchronize to a previous reference with glitch-less operation.


  • Four PLLs for Simultaneous A/V Clock Generation
    • PLL1: 27 or 13.5 MHz
    • PLL2: 148.5 or 74.25 MHz
    • PLL3: 148.5/1.001 or 74.25/1.001 MHz
    • PLL4: 98.304 MHz / 2X (X = 0 to 15)
  • 3 x 2 Video Clock Crosspoint
  • Flexible PLL Bandwidth to Optimize Jitter Performance
    and Lock Time
  • Soft Resynchronization to New Reference
  • Digital Holdover or Free-run on Loss of Reference
  • Status Flags for Loss of Reference and Loss of PLL Lock
  • 3.3 V Single Supply Operation
  • I2C Interface with Address Select Pin
    (3 States)


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Part number Order Rating Operating temperature range (C)
LMH1983 Order now Catalog     -40 to 85    
LMH1981 Order now Catalog     -40 to 85