EVM Stacking
3-3
EVM Operation
3.3
EVM Stacking
EVM stacking is possible if there is a need to evaluate two DAC8534 devices
in yielding a total of eight channel outputs. A maximum of two EVMs are
allowed, since the output terminal J4 dictates the number of DAC channels that
can be connected without colliding. Table 3 - 2 shows how the DAC output
channels are mapped into the output terminal J4, with respect to the jumper
position of W2, W11, W12, and W13.
Table 3 - 2. DAC Output Channel Mapping
Reference
Jumper Position
Function
1 - 2
DAC output A (V
OUT
A) is routed to J4 - 2.
W2
2 - 3
DAC output A (V
OUT
A) is routed to J4 - 10.
1 - 2
DAC output B (V
OUT
B) is routed to J4 - 4.
W11
2 - 3
DAC output B (V
OUT
B) is routed to J4 - 12.
1 - 2
DAC output C (V
OUT
C) is routed to J4 - 6.
W12
2 - 3
DAC output C (V
OUT
C) is routed to J4 - 14.
1 - 2
DAC output D (V
OUT
D) is routed to J4 - 8.
W13
2 - 3
DAC output D (V
OUT
D) is routed to J4 - 16.
In order to allow exclusive control of each stacked EVM, the DAC8534 must
have separate enable signals, EN. This is accomplished by routing the enable
signal of the first EVM through GPIO2 (P2/J2 pin 8), populating R27, and
disconnecting R28. The second EVM should use the GPIO3 (P2/J2 pin12) for
enable signal routing. Also, populate R28 and disconnect R27.
The LDAC signal can be shared to have a synchronous DAC output update.
If you prefer the LDAC signal be separated from each EVM, the same concept
described above should be implemented. Use GPIO0 and R25 for the first
EVM, and GPIO1 and R26 for the second EVM.
3.4
The Output Op Amp
The EVM includes an optional signal conditioning circuit for the DAC output
through an external operational amplifier, U2. Only one DAC output channel
can be monitored at any given time for evaluation since the odd-numbered
pins (J4 - 1 to J4 - 15) are tied together. The output op amp is set to a gain of
2 configuration by default. Nevertheless, the raw outputs of the DAC can be
probed through the even-numbered pins of J4, the output terminal. This
header also provides mechanical stability when stacking, or plugging into any
interface card. In addition, it provides easy access for monitoring up to eight
DAC channels when stacking two EVMs together. See section 3.3.
The following sections describe the different configurations of the output
amplifier, U2.