The Chorus™ Automotive SiT91281 is a low jitter, automotive grade clock generator engineered for applications where reliability and environmental robustness are critical. It comes with a single clock domain, 4 configurable differential or 8 single-ended low skew outputs, and FailSafe™ technology that includes clock safety monitors and programmable alarms.
The SiT91281 integrates SiTime’s MEMS resonator, eliminating the need for an external oscillator or resonator. This integrated MEMS improves system reliability by eliminating traditional clock generators’ dependence on quartz and its associated issues like high failure rates and matching requirements.
The device is configurable in output frequency, output driver types (differential and LVCMOS) and individual output enables through the serial interface. Internal monitoring features help improve system Functional Safety metrics by using the general purpose I/O (GPIO) pins and device registers to report fault conditions to a safety manager MCU.
The SiT91281 is compliant with PCIe Generation 1-6 including configurable spread-spectrum clocking.
User-defined, pre-programmed and user-programmable non-volatile memory (NVM) enables a high degree of flexibility. Configurable GPIO pins support state changes such as individual output enable selection.
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| "Specs" | "Value" |
|---|---|
| Frequency Stability (ppm) | ±50 ppm (-40°C to 125°C), ±20 ppm (-40°C to 105°C) |
| Operating Temperature Range (°C) | -40 to 105, -40 to 125 |
| Package Type (mm²) | 4x4 mm, 24-pin QFN |
| Number of Outputs | 8 single-ended, 4 differential |
| Output Type | LVDS, LPHCSL, LVPECL, HCSL, LVCMOS |
| Output Frequency Range | 1 to 700 MHz (differential), 1 to 220 MHz (LVCMOS) |
| Phase Jitter (rms) | 150 fs (typ.) |
| PCIe Support | Gen 1 to Gen 6 |
| Voltage Supply (V) | 1.8, 2.5, 3.3 |
| Availability | Sampling |
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4x4 mm, 24-pin QFN Clock Generator package
- Frequencies from 1 MHz to 700 MHz
- Fully integrated MEMS-based clock source
- Configurable clock domain and 4 differential outputs or 8 single-ended outputs
- AEC-Q100 Grade 1, -40°C to 125°C
- Excellent frequency stability:
- ±50 ppm (-40°C to 125°C)
- ±20 ppm (-40°C to 105°C)
- Contact SiTime for ±30 ppm (-40°C to 125°C)
- Clock fault monitors (Loss of Lock, Loss of MEMS clock, Output Driver Errors, Die Temperature)
- Supply voltage of 1.8 V to 3.3 V
- Configurable spread-spectrum clock generation
- Low phase jitter, 200 fs maximum (12 kHz-20 MHz)
- PCIe Gen 1 to 6 compliant
- I2C or SPI serial interface for register reads and configuration
- Resistant to shock/vibration
- QFN 24 pin 4 x 4 mm, 0.5 mm pitch (wettable flank) package
- ADAS Computers
- Zonal ECU / Domain ECU
- LiDAR & Radar
- Automotive High-Speed Networking
- SerDes
- Infotainment
- Digital Cockpit Systems
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