Spartan-IIE 1.8V FPGA Fa mily: DC and Switching Characteristics
DS077-3 (v1.0) No vember 15, 2001 www.xilinx.com Modul e 3 of 4
Preliminary Product Specification 1-800-255-7778 11
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Calculation of TIOOP as a Func tion of
Capacitance
TIOOP is the prop agation d elay from the O Input of the IOB
to the pad. The value s for T IOOP a re bas ed on the standard
capacitive load (CSL) for each I/O standard as listed in the
table C onsta nts f or Calcula ting TIOOP, b elow.
F or other capacitive l oads, use the formulas below to calcu-
late an adjusted propagation delay, TIOOP1.
TIOOP1 = TIOOP + A dj + ( C LOAD – CSL) * FL
Where:
Adj i s se lected from IOB Output Delay
Adjustments for Different Stand ards,
page 10, according to the I/O standard used
CLOAD is the capacitive load for the design
FLis the capac itanc e scaling factor
Delay Measurement Methodology
Standard VL(1) VH(1) Meas.
Point VREF
Typ(2)
LVTTL 0 3 1.4 -
LVCMOS2 0 2.5 1.125 -
PCI33_3 Per PCI Spec -
PCI66_3 Per PCI Spec -
GTL VREF – 0.2 VREF + 0. 2 V REF 0.80
GTL+ VREF – 0.2 V REF + 0.2 VREF 1.0
HSTL Class I VREF – 0.5 V REF + 0.5 VREF 0.75
HSTL Class III VREF – 0.5 V REF + 0.5 VREF 0.90
HSTL Class IV VREF – 0.5 VREF + 0. 5 V REF 0.90
SSTL3 I and II VREF – 1.0 V REF + 1.0 V REF 1.5
SSTL2 I and II VREF – 0.75 VREF + 0.75 VREF 1.25
CTT VREF – 0.2 VREF + 0.2 V REF 1.5
AGP VREF –
(0.2xVCCO)VREF +
(0.2xVCCO)VREF Per AGP
Spec
LV DS 1. 2 – 0.125 1.2 + 0.125 1.2
LV PECL 1.6 – 0.3 1.6 + 0.3 1.6
Notes:
1. Input waveform switches between VL and VH.
2. Meas urements are made at VREF Typ, Maximum, and
Minimum. Wors t- case values are r eported.
3. I/O parameter measurements are made wit h the capacitance
value s shown in the foll owing table, Constants for
Calcul ating TIOOP. Refer to Application Note XAPP179 for
appropriate te rminat ions.
4. I/O standard measurements are refl ected in the IBIS model
informati on except where the IBIS f ormat precludes i t.
Constants for Calcul ating TIOOP
Standard CSL(1)
(pF) FL
(ns/pF)
LVTTL Fast Slew Rate, 2 mA drive 35 0.41
LVTTL Fast Slew Rate, 4 mA drive 35 0.20
LVTTL Fast Slew Rate, 6 mA drive 35 0.13
LVT TL Fast Slew Rate, 8 mA dr ive 35 0.079
LVT TL Fast Slew Rate, 12 mA dr ive 35 0.044
LVT TL Fast Slew Rate, 16 mA dr ive 35 0.043
LVT TL Fast Slew Rate, 24 mA dr ive 35 0.033
LVTTL Slow Slew Rate, 2 mA driv e 35 0.41
LVTTL Slow Slew Rate, 4 mA driv e 35 0.20
LVTTL Slow Slew Rate, 6 mA drive 35 0.100
LVTTL Slow Slew Rate, 8 mA drive 35 0.086
LVTTL Slow Slew Rate, 12 mA drive 35 0.058
LVTTL Slow Slew Rate, 16 mA drive 35 0.050
LVTTL Slow Slew Rate, 24 mA drive 35 0.048
LVCMOS2 35 0.041
LVCMOS18 35 0.050
PCI 33 MHz 3.3V 10 0.050
PCI 66 MHz 3.3V 10 0.033
GTL 0 0.014
GTL+ 0 0.017
HSTL Class I 20 0.022
HSTL Class III 20 0.016
HSTL Class IV 20 0.014
SSTL2 Class I 30 0.028
SSTL2 Class II 30 0.016
SSTL3 Class I 30 0.029
SSTL3 Class II 30 0.016
CTT 20 0.035
AGP 10 0.037
Notes:
1. I/ O par ameter measuremen ts are made with the cap acitance
v alu es show n abov e . Refer to Appli cation Note XAPP179 for
appropriate t erminat ions.
2. I/O standard measurements are reflected in the IBIS model
information except wher e the IBIS for mat precludes it.