Device Architecture
2-108 Revision 4
ADC Input Multiplexer
At the input to the Fusion ADC is a 32:1 multiplexer. Of the 32 input channels, up to 30 are user
definable. Two of these channels are hardwired internally. Channel 31 connects to an internal
temperature diode so the temperature of the Fusion device itself can be monitored. Channel 0 is wired to
the FPGA’s 1.5 V VCC supply, enabling the Fusion device to monitor its own power supply. Doing this
internally makes it unnecessary to use an analog I/O to support these functions. The balance of the MUX
inputs are connected to Analog Quads (see the "Analog Quad" section on page 2-83). Tabl e 2- 4 0 defines
which Analog Quad inputs are associated with which specific analog MUX channels. The number of
Analog Quads present is device-dependent; refer to the family list in the "Fusion Family" table on page I
of this datasheet for the number of quads per device. Regardless of the number of quads populated in a
device, the internal connections to both VCC
and the internal temperature diode remain on Channels 0
and 31, respectively. To sample the internal temperature monitor, it must be strobed (similar to the AT
pads). The TMSTBINT pin on the Analog Block macro is the control for strobing the internal temperature
measurement diode.
To determine which channel is selected for conversion, there is a five-pin interface on the Analog Block,
CHNUMBER[4:0], defined in Ta b le 2 - 3 9 .
Table 2-40 shows the correlation between the analog MUX input channels and the analog input pins.
Table 2-39 • Channel Selection
Channel Number CHNUMBER[4:0]
0 00000
1 00001
2 00010
3 00011
.
.
.
.
.
.
30 11110
31 11111
Table 2-40 • Analog MUX Channels
Analog MUX Channel Signal Analog Quad Number
0 Vcc_analog
1 AV0 Analog Quad 0
2AC0
3AT0
4 AV1 Analog Quad 1
5AC1
6AT1
7 AV2 Analog Quad 2
8AC2
9AT2
10 AV3 Analog Quad 3
11 AC3
12 AT3
13 AV4 Analog Quad 4
14 AC4
15 AT4