DS692 Datasheet, PDF (19/41 Pages) Xilinx, Inc – Radiation-Hardened

Radiation-Hardened, Space-Grade Virtex-5QV FPGA Data Sheet: DC and AC Switching Characteristics
Output Delay Measurements
Output delays are measured using a Tektronix P6245 TDS500/600 probe (< 1 pF) across approximately 4 inches of FR4
microstrip trace. Standard termination was used for all testing. The propagation delay of the 4-inch trace is characterized
separately and subtracted from the final measurement, and is therefore not included in the generalized test setups shown in
Figure 6 and Figure 7.
X-Ref Target - Figure 6
V_REF
FPGA Output
R_REF
X-Ref Target - Figure 7
V_MEAS
(voltage level when taking
delay measurement)
C_REF
(probe capacitance)
DS692_06_031510
Figure 6: Single-Ended Test Setup
FPGA Output
+
C_REF
R_REF V_MEAS
–
DS692_07_031510
Figure 7: Differential Test Setup
Measurements and test conditions are reflected in the IBIS models except where the IBIS format precludes it. Parameters
V_REF, R_REF, C_REF, and V_MEAS fully describe the test conditions for each I/O standard. The most accurate prediction of
propagation delay in any given application can be obtained through IBIS simulation, using the following method:
1. Simulate the output driver of choice into the generalized test setup, using values from Table 31.
2. Record the time to V_MEAS.
3. Simulate the output driver of choice into the actual PCB trace and load, using the appropriate IBIS model or capacitance
value to represent the load.
4. Record the time to V_MEAS.
5. Compare the results of steps 2 and 4. The increase or decrease in delay yields the actual propagation delay of the PCB
trace.
Table 31: Output Delay Measurement Methodology
Description
I/O Standard Attribute
LVTTL (Low-Voltage Transistor-Transistor Logic)
LVCMOS (Low-Voltage CMOS), 3.3V
LVCMOS, 2.5V
LVCMOS, 1.8V
LVCMOS, 1.5V
LVCMOS, 1.2V
PCI (Peripheral Component Interface), 33 MHz, 3.3V
LVTTL (all)
LVCMOS33
LVCMOS25
LVCMOS18
LVCMOS15
LVCMOS12
PCI33_3 (rising edge)
PCI33_3 (falling edge)
R_REF
( Ω)
1M
1M
1M
1M
1M
1M
25
25
C_REF⁽¹⁾
( pF )
0
0
0
0
0
0
10⁽²⁾
10⁽²⁾
V_MEAS
(V)
1.4
1.65
1.25
0.9
0.75
0.6
0.94
2.03
V_REF
(V)
0
0
0
0
0
0
0
3.3
DS692 (v1.3.1) January 16, 2015
Product Specification
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