Sundance SMT399-160 - Manual (Page 11)

4.5 On-board crystal.
The AD9954 are clocked from a crystal (20MHz). The master DDS then passes the sampling
clock to the slave DDS to ensure synchronisation. Synchronisation can also be achieved when
cascading several SMT399-160 daughter modules. There is an automatic synchronisation
available from the DDS registers.
4.6 Output Variable Gain Amplifier.
Each output is driven by a Variable Gain Amplifier (VGA – AD8370 ), digitally controlled that
uses 8 bits to code the gain and provides a power-down mode. Two ranges of gains are
available: from –11 to +17dBs or from +6 to +34dBs.
4.7 Daughter sub-module interface.
The link between the main and the daughter sub-module is made via two Samtec connectors.
There is no fast signal travelling between both cards. The first connector passes control
signals and the second one passes a 3.3-volt and 5-volt supplies and a ground between sub-
modules.
The female differential connector is located on the main module. The Samtec Part Number
for this connector is QTH-060-01-F-D-DP-A.
The female power connector is located on the main module. The Samtec Part Number for this
connector is BKS-133-03-F-V-A
The male differential connector is located on the daughter card. The Samtec Part Number for
this connector is QSH-060-01-F-D-DP-A
The male power connector is located on the daughter card. The Samtec Part Number for this
connector is BKT-133-03-F-V-A
The mated height between the main module and the daughter card is 5 mm.
4.8 Cascading modules
Several SMT399-160s can be cascaded. All DDSs can be synchronised by linking the modules
via connectors J1 and J3, both are 2-mm 3-pin headers. J1 of the master module should be
connected to J3 of the slave module as follows:
SMT399-160
Master (J1)
SMT399-160
Slave (J3)
Crystal Out
(J1 – pin 1)
Crystal In
(J3 – pin 3)
Gnd
(J1 – pin 2)
Gnd
(J3 – pin 2)
Synch In
(J1 – pin 3)
Synch Out
(J3 – pin 1)
Figure 4 - Connections for cascading modules.
User Manual SMT399-160 Page 11 of 39 Last Edited: 24/05/2007 17:12:00