HD74LS123 datasheet(4/9 Pages) RENESAS

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HD74LS123

Rev.2.00, Feb.18.2005, page 4 of 8

Switching Characteristics

(VCC = 5 V, Ta = 25°C)

Item

Symbol

Inputs

Outputs

min.

typ.

max.

Unit

Condition

tPLH

—

tPHL

—

tPLH

—

tPHL

—

tPLH

—

Propagation delay

time

tPHL

CLR

—

Cext = 0, Rext = 5 k

Ω,

CL = 15 pF, RL = 2 k

Ω

t(out)min

—

116

200

Output pulse width

t(out)

A, B

4.5

µs

Cext = 1000 pF,

Rext = 10 k

Ω,

CL = 15 pF, RL = 2 k

Ω

Typical Application Data for HD74LS123

For pulse widths when Cext

≤ 1000 pF, See Figure 3.

The output pulse is primarily a function of the external capacitor and resistor. For Cext > 1000 pF, the output pulse

width (tw) is defined as: tw(out) = K

• R

ext

• C

ext; See Figure 4.

VCC

Rext (k

Ω)

Cext (pF)

tw(out) (ns)

Rext

to Rext/Cext

to Cext

Cext

–

Figure 2

Timing Component Connections

100

1,000

100

1,000

10,000

100,000

External capacitance Cext (pF)

Rext = 80k

Ω

40k

Ω

20k

Ω

10k

Ω

Rext = 160k

Ω

Figure 3

Typical Output Pulse Width (Cext

≤ 1000 pF)

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