| 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 |
- 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.
