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TIBPAL16L8-5C Datasheet, PDF (24/30 Pages) Texas Instruments – HIGH-PERFORMANCE IMPACT-X E PAL CIRCUITS | |||
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TIBPAL16R4-5C, TIBPAL16R6-5C, TIBPAL16R8-5C
HIGH-PERFORMANCE IMPACT-X ⢠PAL® CIRCUITS
SRPS011D â D3359, OCTOBER 1989 â REVISED SEPTEMBER 1992
By using the described test circuit, MTBF can be determined for several different values of ât (see Figure 9).
Plotting this information on semilog scale demonstrates the metastable characteristics of the selected flip-flop.
Figure 11 shows the results for the TIBPAL16â-5C operating at 1 MHz.
10 9
10 yr
10 8
1 yr
10 7
1 mo
10 6
1 wk
10 5
1 day
10 4
1 hr
10 3
10 2
1 min
10 1
10 s
fclk = 1 MHz
fdata = 500 kHz
0 10 20 30 40 50 60 70
â t â Time Difference â ns
Figure 11. Metastable Characteristics
From the data taken in the above experiment, an equation can be derived for the metastable characteristics at
+ * other clock frequencies.
The metastable equation: 1
MTBF
fSCLK x fdata x C1 e ( C2 x Dt)
The constants C1 and C2 describe the metastable characteristics of the device. From the experimental data,
these constants can be solved for: C1 = 4.37 X 10â3 and C2 = 2.01
+ * * Therefore
1
MTBF
fSCLK x fdata x 4.37 x 10 3 e ( 2.01 x Dt)
definition of variables
DUT (Device Under Test): The DUT is a 5-ns registered PLD programmed with the equation Q : = D.
MTBF (Mean Time Between Failures): The average time (s) between metastable occurrences that cause a
violation of the device specifications.
fSCLK (system clock frequency): Actual clock frequency for the DUT.
fdata (data frequency): Actual data frequency for a specified input to the DUT.
C1: Calculated constant that defines the magnitude of the curve.
C2: Calculated constant that defines the slope of the curve.
trec (metastability recovery time): Minimum time required to guarantee recovery from metastability, at a given
MTBF failure rate. trec = ât â tpd (CLK to Q, max)
ât: The time difference (ns) from when the synchronizing flip-flop is clocked to when its output is sampled.
The test described above has shown the metastable characteristics of the TIBPAL16R4/R6/R8-5C series. For
additional information on metastable characteristics of Texas Instruments logic circuits, please refer to TI
Applications publication SDAA004, âMetastable Characteristics, Design Considerations for ALS, AS, and LS
Circuits.ââ
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