Sundance SMT712 - Manual (Page 24)

User Manual SMT712 Page 24 of 89 Last Edited: 11/12/2012 10:36:00
4.5.10 Power dissipation
The PXI Express chassis receiving the SMT712 module should provide enough forced
air flow in order to dissipate the heat generated by the module. The air flow must be
going against gravity or upwards, as specified in the PXI Specification.
The FPGA is fitted with a heatsink to keep it within an appropriate range of
temperature (no more than 85 ºC) when using the default firmware provided.
Nevertheless the board requires some forced cooling. It is recommended to use a
PXIe-1062Q chassis or equivalent from National instrument as it already integrates a
built-in regulated cooling system. Measurements have been made using a PXIe-
1062Q on the maximum fan speed setting and the standard firmware with both
DACs clocked at 2,3GHz (both DDR2 memory banks used as a pattern generator):
In an ambient temperature of 25 ºC, the FPGA die temperature stays close to 60 ºC.
In an ambient temperature of 30 ºC, the FPGA die temperature stays close to 70 ºC.
In order to improve the heat dissipation is a system, some slot blockers can be used
(from National Instrument), which redirect the air flow of non-used slots to where it
is needed. Keeping the FPGA die temperature below 70-75 ºC ensures constant
performance in time.
The temperature of the FPGA die is available within the register to read-back so it
can be monitored.
It is also specified that a 3U PXI Express module should not dissipate more than 30
Watts of heat.
The following picture shows the direction of the forced air flow across a 3U PXI
Express module:
Figure 11 - Forced airflow for a 3U module.
A PXI Express rack has a capacity of dissipating 30 watts of heat per slot using
forced air-cooling system via typically two 110-cfm fans with filter.
4.5.11
JTAG
A connector (J8) is specifically dedicated for FPGA and CPLD detection and
programming. Both the CPLD and the FPGA are part of the JTAG chain. A 14-