rtd IDAN-SK-SYNC25104HRS, User Manual, Page: 15 / 31

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SYNC25104HR/
SYNC35104HR
User’s Manual
Table 5: SyncBus lane assignments
SyncBus lane Description
0 1 PPS signal
1 SI5395 output 1
2 SI5395 output 0
3 10MHz
CN6: Any Frequency Output
CN6 is a 16-pin header which connects to 4 outputs of the SI5395 clock synthesizer chip. The outputs can be configured by the Silabs CBPro
software and the configuration file can be downloaded to the chip by the supplied software. The outputs are DC coupled. Note that it is
theoretically possible to use these outputs as single ended, it is recommended to use them for differential signaling only. For single-ended
signals use CN10 and CN11. Table 6 lists the pinout of the connector, the names correspond to the outputs of SI5395. When interfacing to this
connector it is recommended to minimize the length of cable and route it inside a shielding metal enclosure. If it is necessary to run the cable
several feet or further, it is recommended to use shielded cable (eg. SFTP).
Table 6: CN6 Any frequency output
Pin Name Pin # Pin # Pin Name
Output 5- 2 1 Output 5+
GND 4 3 GND
Output 4- 6 5 Output 4+
GND 8 7 GND
Output 3- 10 9 Output 3+
GND 12 11 GND
Output 2- 14 13 Output 2+
GND 16 15 GND
CN7: GPS Antenna Connector
The SYNC35104HR/25104HR provides an MCX connector for the GPS antenna. The 3.3V antenna bias can be turned on or off using JP2.
CN8: Time Mark Input
The LEA-M8F module can also be used for precise time measurements using the Time mark input. Rising edges of these signals are time-
stamped with respect to the receiver’s active time-base. Time-stamps are reported in the UBX-TIM-TM2 message. CN8 connects to
FREQ_PHASE_IN1 of the u-blox GNSS receiver module.
CN9: 1PPS Output
CN9 is a 1PPS output which is buffered by a low propagation delay buffer. The output is DC coupled, has 50Ω impedance, its level is 3.3Vpp.
The total delay from the GNSS receiver’s output pad to the connector is 1.94ns typical 2.44ns maximum.
CN10 and CN11: Any Frequency Outputs
CN10 and CN11 are coaxial sockets which connect to SI5395 clock synthesizer chip. The outputs can be configured by the Silabs CBPro
software and the configuration file can be downloaded to the chip by the supplied software. The outputs are DC coupled and the level is 3.3Vpp
when using LVCMOS output buffer setting (recommended) and the output is not terminated. If differential signaling is required use CN6.
CN12: 10MHz Output
CN12 is a buffered output of the oven-controlled crystal oscillator (OCXO). This output is DC coupled, has 50Ω impedance, and the level is
3.3Vpp.
CN7-CN12 are MMCX connectors:
Connector Part #: Amphenol 908-22106 Example Mating Connector: Amp 901-9877-RFX
CN13: Serial I/O Connector
CN12 is an RS-232 interface that is connected to the GPS receiver. Table 7 has the pin-out. RX and TX lines are connected according to the
DCE pinout (ie. RX is a driven output, TX is an input). RI, DCD and DSR pins are connected together and driven by 1pps signal. This can be
used by various software to synchronize the internal clock of the CPU. This serial port is also routed to the USB-serial converter. The TX output
of the GPS receiver is permanently connected to the RX input of the USB-serial converter, and the RX pin of CN12. The GPS RX however has
a signal switch which is activated whenever a byte is transmitted from the USB. When there is no transmission from the bus, the RX is switched
to the RS232 TX input. RTS and DTR pins are not used and are pulled to GND with 10k. CTS is not connected.