74HCT240 datasheet(8/18 Pages) NXP

8 / 18 page

74HC_HCT240_3

Product data sheet

Rev. 03 — 2 August 2007

8 of 18

NXP Semiconductors

74HC240; 74HCT240

Octal buffer/line driver; 3-state; inverting

[1]

tpd is the same as tPHL and tPLH.

[2]

ten is the same as tPZH and tPZL.

[3]

tdis is the same as tPHZ and tPLZ.

[4]

tt is the same as tTHL and tTLH.

[5]

CPD is used to determine the dynamic power dissipation (PD in µW):

PD =CPD × VCC2 × fi × N+ ∑ (CL × VCC2 × fo) where:

fi = input frequency in MHz;

fo = output frequency in MHz;

CL = output load capacitance in pF;

VCC = supply voltage in V;

N = number of inputs switching;

∑ (C

L × VCC

× f

o) = sum of outputs.

11. Waveforms

74HCT240

tpd

propagation delay

nAn to nYn;

see Figure 6

[1]

VCC = 4.5 V

VCC = 5.0 V; CL =15pF

ten

enable time

nOE to nYn; VCC = 4.5 V; see

Figure 7

[2]

-13

3038

tdis

disable time

nOE to nYn; VCC = 4.5 V; see

Figure 7

[3]

-13

2531

transition time

VCC = 4.5 V; see Figure 6

[4]

CPD

power dissipation

capacitance

per transceiver;

VI = GND to VCC − 1.5 V

[5]

-30-

Table 7.

Dynamic characteristics …continued

GND = 0 V; for load circuit see Figure 8.

Symbol Parameter

Conditions

°C

−40 °C to +125 °C Unit

Min

Typ

Max

(85

°C)

Max

(125

°C)

Measurement points are given in Table 8.

VOL and VOH are typical voltage output drop that occur with the output load.

Fig 6.

Input (nAn) to output (nYn) propagation delays and output transition times

mgu781

nAn input

nYn output

tPHL

tPLH

GND

VOH

VOL

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