HD74LS251

Rev.3.00, Jul.15.2005, page 4 of 5

Testing Method

Test Circuit

W

Y

S

Same as Load Circuit 1.

Output

Input

P.G.

Ω

5k

Ω

Load circuit 1

Output

B

C

A

4.5V

Notes:

1.

2.

All diodes are 1S2074(H).

Waveform

Enable

Waveform 1

Waveform 2

1.3V

1.3V

1.3V

1.3V

0.5V

0.5V

0V

0V

0V

3V

3V

4.5V

10%

10%

90%

90%

1.5V

1.5V

Notes:

1.

≤ 15 ns, t

THL

≤ 6 ns, PRR = 1 MHz, duty cycle = 50%

2.

Waveform 1 is for an output with internal conditions such that the output is low except when

disabled by the output control.

3.

Waveform 2 is for an output with internal conditions such that the output is high except when

disabled by the output control.