The SMT-FMC116 is an FMC digitiser module equipped with one, two, three or four LTC217x ADCs with speeds up to 125Msps @ 14-bit resolution. It uses an HPC FMC connector and complies with ANSI/VITA 57.1. The simplified block diagram is presented in Figure 1.
In addition to ADCs, it is equipped with a clock distribution unit, which allows the selection of sampling clocks based on several clock sources (front panel input, FMC input or internal clock reference) and additional functional elements such as board management/monitoring and power distribution.
ADC and Analog Input Path
The LTC2175-14/LTC2174-14/LTC2173-14 are 4-channel, simultaneous sampling 14-bit A/D converters designed for digitising high frequency, wide dynamic range signals. The digital outputs are serial LVDS (with optional internal termination) to minimise the number of data lines. Each channel outputs two bits at a time (2-lane mode), resulting in data rates of up to 1 Gbps on a single data lane. The receiver used on the carrier must be able to accommodate such a data stream.
Analog Input path consists of a true differential operational amplifier for DC-coupled version or transformer for AC-coupled one. In both cases, the accepted input signal levels are 2 Vpp. The analogue input bandwidth on board is limited to 100 MHz (> Nyquist frequency).
The board is equipped with several input connectors to provide interfaces for the user. This includes:
- Clock: MMCX connector dedicated for single-ended external input clock. The signal can be routed (via clock distribution unit) to ADCs (as main clock) and to user application level via dedicated pins of the HPC FMC connector.
- Trigger: MMCX connector for external trigger input – the signal is buffered and connected to the FMC connector for use on the user application level.
- Analog Input: Samtec’s ACCELERATE® ARF6-RA Right Angle connector connects analogue signals to the board. The connector and the mating cable provide sufficient analogue performance. The selection of break-out boards offered by Sundance allows easy integration with any user application/system.
All internal power supplies are derived from 12V and 3.3V FMC, using high-performance, low-noise DC/DC converters and LDOs. The board does not limit VADJ supply voltage to fit a wide range of carrier boards on the market.
Board management consists of standard elements required by FMC specification (ID EPROM and Power management interface) extended by additional temperature sensors on the management I2C bus for constant monitoring with over-temperature protection.
The board uses HPC FMC with the fastest lines running at 1 Gbps (ADC data lines). 4-channels, 8-channels and 12-channels versions are also compatible with the LPC interface, however, Power Good Monitoring and c2m_clk lines are unavailable for user application.