
Spartan-3 FPGA Family: Functional Description
DS099 (v3.1) June 27, 2013
Product Specification
15
Differential standards employ a pair of signals, one the opposite polarity of the other. The noise canceling (e.g.,
Common-Mode Rejection) properties of these standards permit exceptionally high data transfer rates. This section
introduces the differential signaling capabilities of Spartan-3 devices.
Each device-package combination designates specific I/O pairs that are specially optimized to support differential
standards. A unique “L-number”, part of the pin name, identifies the line-pairs associated with each bank (see
Figure 40,page 112). For each pair, the letters ‘P’ and ‘N’ designate the true and inverted lines, respectively. For example, the pin
names IO_L43P_7 and IO_L43N_7 indicate the true and inverted lines comprising the line pair L43 on Bank 7. The VCCO
lines provide current to the outputs. The VCCAUX lines supply power to the differential inputs, making them independent of
the VCCO voltage for an I/O bank. The VREF lines are not used. Select the VCCO level to suit the desired differential standard
Table 8: Single-Ended I/O Standards
Signal Standard
(IOSTANDARD)
VCCO (Volts)
VREF for Inputs
Board Termination
Voltage (VTT) in Volts
For Outputs
For Inputs
GTL
0.8
1.2
GTLP
11.5
HSTL_I
1.5
–
0.75
HSTL_III
1.5
–0.9
1.5
HSTL_I_18
1.8
–0.9
0.9
HSTL_II_18
1.8
–0.9
0.9
HSTL_III_18
1.8
–1.1
1.8
LVCMOS12
1.2
–
LVCMOS15
1.5
–
LVCMOS18
1.8
–
LVCMOS25
2.5
–
LVCMOS33
3.3
–
LVTTL
3.3
–
PCI33_3
3.0
–
SSTL18_I
1.8
–0.9
0.9
SSTL18_II
1.8
–0.9
0.9
SSTL2_I
2.5
–
1.25
SSTL2_II
2.5
–
1.25
Notes:
1.
Banks 4 and 5 of any Spartan-3 device in a VQ100 package do not support signal standards using VREF.
2.
The VCCO level used for the GTL and GTLP standards must be no lower than the termination voltage (VTT), nor can it be lower than the
voltage at the I/O pad.
3.
See
Table 10 for a listing of the single-ended DCI standards.