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SWITCHING CHARACTERISTICS, 5-V NOMINAL SUPPLY

TB5D1M, TB5D2H

SLLS579C – SEPTEMBER 2003 – REVISED JANUARY 2008

THIRD STATE—A TB5D1M (or TB5D2H) driver produces pseudo-ECL levels, and has a third-state mode, which

is different than a conventional TTL device. When a TB5D1M (or TB5D2H) driver is placed in the third state, the

base of the output transistors is pulled low, bringing the outputs below the active-low level of standard PECL

devices. [For example: The TB5D1M low output level is typically 2.7 V, while the third state output level is less

than 0.1 V.] In a bidirectional, multipoint, bus application, the driver of one device, which is in its third state, may

be back driven by another driver on the bus whose voltage in the low state is lower than the third-stated device.

This could come about due to differences in the driver's independent power supplies. In this case, the device in

the third state controls the line, thus clamping the line and reducing the signal swing. If the difference voltage

between the independent driver power supplies is small, this consideration can be ignored. Again using the

TB5D1M driver as an example, a typical supply voltage difference between separate drivers of > 2 V can exist

without significantly affecting the amplitude of the signal.

over recommended operating conditions unless otherwise noted

parameter

test conditions

min

max

unit

1.2

2

ns

Figure 3

1.2

2

Capacitive delay

0.01

0.03

ns/pF

Propagation delay time,

7

12

high-level-to-high-impedance output

Propagation delay time,

7

12

low-level-to-high-impedance output

ns

Figure 3

Propagation delay time,

5

12

high-impedance-to-high-level output

Propagation delay time,

4

12

high-impedance-to-low-level output

0.15

0.3

0.15

1.1

ns

Figure 3

0.1

1

0.3

Rise time (20% - 80%)

0.7

2

ns

Figure 3

Fall time (80% - 20%)

0.7

2

(1)

All typical values are at 25C and with a 5-V supply.

(2)

(3)

when both devices operate with the same supply voltage, at the same temperature, and have identical packages and test circuits.

(4)

4

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