ABT22V10A5 データシートの表示（PDF） - Philips Electronics

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ABT22V10A5

5V high-speed universal PLD device with live insertion capability

Philips Electronics 

Philips Semiconductors

5V high-speed universal PLD device

with live insertion capability

Product specification

ABT22V10A5, A7

Metastable Characteristics

Philips provides complete data on the ABT22V10A5’s metastable

characteristics. While the ABT22V10A5 does not employ Philips

patented metastable immune flip-flop, its metastabel characteristics

are still quite favorable relative to competitive devices. For

information on metastable immune PLDs, refer to the datasheets for

the ABT22V10-7 for 5V applications or the LVT22V10-7 for 3.3V

designs.

Design Example

Suppose a designer wants to use the ABT22V10A5 for

synchronizing asynchronous data that is arriving at 10MHz (as

measured by a frequency counter), in a 5V system that has a clock

frequency of 50MHz, at an ambient temperature of 25°C. The next

device in the sytem samples the output fo the ABT22V10A5 5.5ns

after the clock edge to ensure that any metastable conditions that

occur have time to resolve to the correct state. The MTBF for this

situatio can be calcuclated by using the equation below:

MTBF = e(tȀ/τ)/T0FCF1

In this formula, FC is the frequency of the clock, F1 is the average

input event frequency, and tȀ is the time after the clock pulse that the

output is sampled (tȀ > TCO). T0 and τ are device parameters

provided by the semiconductor manufacturer (refer to Table 1 for the

ABT22V10A5 metastability specifications). T0 and τ are derived

from tests and can be most nearly be defined as follows: τ is a

function of the rate at which a latch in a metastable state resolves

that condition. T0 is a function of the measurement of the propensity

of a latch to enter a metastable state. T0 is also a normalization

constant which is a very strong function of the normal propagation

dely of the device.

In this situation, the F1 will be twice that data frequency, or 20MHz,

because input events consist of both low and high transitions. Thus

in this case FC is 50MHz, F1 is 20MHz, τ is 85.6ps, tȀ is 5.5ns, and

T0 is 4.55 seconds. Using the above formula, the actual MTBF for

this situation is 1.76 × 1012 seconds, or 55,889 years for the

ABT22V10A5.

Table 1. Typical Values for τ and T0 at various VCC’s and Temperatures

0°C

+25°C

VCC

5.25V

τ

72.00ps

T0

7.20E+01

τ

96.70ps

T0

4.59E–01

5.00V

72.80ps

2.06E+02

85.60ps

4.55E+00

4.75V

68.70ps

9.97E+03

81.70ps

4.85E+01

τ

105.00ps

100.00ps

99.80ps

+75°C

T0

1.43E–01

8.37E–01

1.29E+00

1996 Dec 16

7

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