Lime-GPSDO v1.0 hardware description

Lime-GPSDO Board Key Features

The Lime-GPSDO development board provides high stability clock source for timing sensitive applications. Clock frequency is being constantly monitored inside MAX10 FPGA and tuned by PPS signal from GNSS module.

Lime-GPSDO v1.0

For more information on the following topics, refer to the respective documents:

• MAX10 device family, refer to Intel documentation link
• N20B GNSS module resources link

Lime-GPSDO board features:

• USB Interface
  • Silicon labs USBXpress Family USB-to-UART bridge CP2102N.
• FPGA Features
  • MAX10 10M16SAU169C8 device in 169-pin UBGA
  • 16K logic elements
  • 549 Kbits embedded memory (M9K) and 2368 Kbits of user Flash Memory
  • 45 embedded 18x18 multipliers
  • 1 PLLs
• FPGA Configuration
  • JTAG mode configuration
• Memory Devices
  • 4Mbit FLASH
  • 128Kbit (16K x 8) EEPROM
• Connections
  • microUSB2.0 (type B)
  • SMA connectors for clock IN/OUT, time pulse output and GNSS antenna
  • FPGA GPIO header (0.05” pitch)
  • FPGA JTAG connectors (0.05” pitch and side connector)
  • 5V DC power jack and pinheader
  • Backup battery connector for GNSS receiver
  • Clock output pinheader
  • External UART connector
  • External I2C connector
• Clock System
  • 30.72MHz VCOCXO:
    • Frequency calibration ±0.5ppm;
    • Frequency stability over temperature in still air ±20ppb;
    • Frequency slope ΔF/ΔT in still air ±1.2ppb/°C
  • Possibility to tune VCOCXO by onboard DAC
  • Possibility to use GNSS PPS signal as a reference when tuning VCOCXO frequency
• Board Size without connectors 50.50mm x 80mm (1.99” x 3.15”)

Board Overview

Lime-GPSDO board version 1.0 picture with highlighted major components and connections presented in Figure 1 and Figure 2. There are three connector types – data and debugging (USB2.0, FPGA GPIO and JTAG), power (DC jack and external supply pinheader), clock source output, GNSS antenna and time pulse output.