2:8 fanout at 267 MHz — PCIe clock distribution without PLL jitter
The SY75578LMG is a 2:8 fanout clock buffer from Microchip's Precision Edge® family, designed to distribute a PCIe reference clock without adding PLL-induced jitter — there is no internal PLL, so the output jitter tracks the input source. It accepts HCSL or LVDS inputs and outputs eight HCSL copies at up to 267 MHz, covering PCIe Gen1 (100 MHz), Gen2 (100 MHz), and Gen3 (100 MHz) base clock rates with margin. The differential input-to-output path is transparent — the input is AC-coupled, and the output is HCSL with a controlled swing that meets the PCIe reference clock specification without external termination resistors.
Industrial temperature range and supply tolerance
The supply range is 3.135 V to 3.465 V — a 3.3 V nominal rail with ±5 % tolerance stays inside this window, but a 3.0 V rail does not; the board must regulate to 3.3 V. Single-circuit design (one buffer channel) with a 2:8 input-to-output ratio means two independent clock inputs each fan out to four outputs, or one input fans out to all eight when the second input is unused.
32-QFN with exposed pad — thermal and layout notes
Packaged in a 32-VFQFN with exposed pad, 5x5 mm body. The pad also serves as the low-inductance return path for the HCSL outputs — a poor ground connection raises output jitter above the datasheet limit.