HD74LS251 Datasheet, PDF (4/6 Pages) Hitachi Semiconductor – 1 of 8 Data Selectors/Multiplexers(with strobe and three-state outputs)

HD74LS251
Testing Method
Test Circuit
4.5V
P.G.
Zout = 50Ω
Input
V_CC
Load circuit 1
RL
S
Output
S1
D0
D1
W
D2
D3
5kΩ
D4
S2
CL
D5
D6
D7
Output
A
B
Y
Same as Load Circuit 1.
C
Notes: 1. C_L includes probe and jig capacitance.
2. All diodes are 1S2074(H).
Waveform
Enable
t_THL
90%
1.3V
10%
t_ZL
Waveform 1
S1 closed,
S2 open _1.3V
t_ZH
Waveform 2
1.3V
S1 open, S2 closed
t_TLH
3V
90%
3V
1.3V
10%
0V
0V
4.5V
V_OL
V_OH
0V
t_LZ
S1 and,
S2 closed
1.5V
V_OL
t_HZ
0.5V
V_OH
0.5V
S1 and, S2 closed
1.5V
Notes:
1. Input pulse; t_TLH ≤ 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.
Rev.3.00, Jul.15.2005, page 4 of 5