IDT5T9010
INDUSTRIALTEMPERATURERANGE
2.5VPROGRAMMABLESKEWPLLCLOCKDRIVER TERACLOCK
PROGRAMMABLESKEW
Output skew with respect to the REF[1:0] and REF[1:0]/VREF[1:0] input by the nF[2:0]/FBF[2:0] control pins. In order to minimize the number of
is adjustable to compensate for PCB trace delays, backplane propaga- control pins, 3-level inputs (HIGH-MID-LOW) are used, they are in-
tion delays or to accommodate requirements for special timing relation- tended for but not restricted to hard-wiring. Undriven 3-level inputs
ships between clocked components. Skew is selectable as a multiple of a default to the MID level. The Control Summary Table shows how to
time unit (tU) which ranges from 250ps to 1.25ns (see Programmable select specific skew taps by using the nF[2:0]/FBF[2:0] control pins.
Skew Range and Resolution Table). There are 18 skew/divide configu-
rations available for each output pair. These configurations are chosen
EXTERNALDIFFERENTIALFEEDBACK
By providing a dedicated external differential feedback, the IDT5T9010
An internal loop filter moderates the response of the VCO to the
gives users flexibility with regard to skew adjustment. The FB and FB/ phase detector. The loop filter transfer function has been chosen to
VREF2 signals are compared with the input REF[1:0] and REF[1:0]/VREF[1:0] provide minimal jitter (or frequency variation) while still providing accu-
signals at the phase detector in order to drive the VCO. Phase differ- rate responses to input frequency changes.
ences cause the VCO of the PLL to adjust upwards or downwards
accordingly.
PROGRAMMABLESKEWRANGEANDRESOLUTIONTABLE
FS = LOW
1/(16 x FNOM)
50 to 125MHz
FS = HIGH
1/(16 x FNOM)
100 to 250MHz
Comments
TimingUnitCalculation(tU)
VCOFrequencyRange(FNOM)(1,2)
SkewAdjustmentRange(3)
MaxAdjustment:
±8.75ns
±157.5°
±43.75%
tU =1.25ns
tU =0.833ns
tU =0.625ns
—
±4.375ns
±157.5°
ns
PhaseDegrees
% of Cycle Time
±43.75%
—
Example 1, FNOM = 50MHz
Example 2, FNOM = 75MHz
Example 3, FNOM = 100MHz
Example 4, FNOM = 150MHz
Example 5, FNOM = 200MHz
Example 6, FNOM = 250MHz
—
tU =0.625ns
tU =0.417ns
tU =0.313ns
tU =0.25ns
—
—
NOTES:
1. The device may be operated outside recommended frequency ranges without damage, but functional operation is not guaranteed.
2. The level to be set on FS is determined by the nominal operating frequency of the VCO and Time Unit Generator. The VCO frequency always appears at nQ[1:0] outputs when
they are operated in their undivided modes. The frequency appearing at the REF[1:0] and REF[1:0]/VREF[1:0] and FB and FB/VREF2 inputs will be FNOM when the QFB and QFB
are undivided and DS[1:0] = MM. The frequency of the REF[1:0] and REF[1:0]/VREF[1:0] and FB and FB/VREF2 inputs will be FNOM /2 or FNOM /4 when the part is configured for
frequency multiplication by using a divided QFB and QFB and setting DS[1:0] = MM. Using the DS[1:0] inputs allows a different method for frequency multiplication (see Divide
Selection Table).
3. Skew adjustment range assumes that a zero skew output is used for feedback. If a skewed QFB and QFB output is used for feedback, then adjustment range will be greater.
For example if a 4tU skewed output is used for feedback, all other outputs will be skewed –4tU in addition to whatever skew value is programmed for those outputs. ‘Max adjustment’
range applies to all output pairs where ±7tU skew adjustment is possible and at the lowest FNOM value.
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