Product details

Function Clock generator Number of outputs 4 Output frequency (max) (MHz) 148.5 Core supply voltage (V) 3.3 Output supply voltage (V) 3.3 Input type LVCMOS Output type LVDS Operating temperature range (°C) -40 to 85 Features 3G/HD/SD video clock generator with audio clock Rating Catalog
Function Clock generator Number of outputs 4 Output frequency (max) (MHz) 148.5 Core supply voltage (V) 3.3 Output supply voltage (V) 3.3 Input type LVCMOS Output type LVDS Operating temperature range (°C) -40 to 85 Features 3G/HD/SD video clock generator with audio clock Rating Catalog
WQFN (RTA) 40 36 mm² 6 x 6
  • 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)
  • 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)

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.

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.

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Technical documentation

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Type Title Date
* Data sheet LMH1983 3G/HD/SD Video Clock Generator with Audio Clock datasheet (Rev. I) PDF | HTML 02 Dec 2014
Selection guide Broadcast and Professional Video Interface Solutions (Rev. E) 05 Apr 2017
Application note AN-2108 Generating 44.1 kHz Based Clocks with the LMH1983 (Rev. A) 26 Apr 2013
User guide LMH1983 Evaluation Kit Users Guide 25 Jan 2012
Design guide Broadcast Video Owner's Manual 17 Nov 2006

Design & development

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LMH1983 IBIS Model

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Reference designs

TIDA-00424 — Video Sync and Video Clock Generation and Distribution Reference Design

A video clock sub-system designed to perform video sync separation and derives synchronous video clocks for video and audio sub-systems.
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