74HC238 datasheet(8/18 Pages) NXP

8 / 18 page

74HC_HCT238_3

Product data sheet

Rev. 03 — 16 July 2007

8 of 18

NXP Semiconductors

74HC238; 74HCT238

3-to-8 line decoder/demultiplexer

[1]

tpd is the same as tPHL and tPLH.

[2]

tt is the same as tTHL and tTLH.

[3]

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

74HCT238

tpd

propagation delay

An to Yn; see Figure 6

[1]

VCC = 4.5 V

VCC = 5.0 V; CL =15pF

E3 to Yn; see Figure 6

[1]

VCC = 4.5 V

VCC = 5.0 V; CL =15pF

En to Yn or see Figure 7

[1]

VCC = 4.5 V

VCC = 5.0 V; CL =15pF

transition time

VCC = 4.5 V;

see Figure 6 and Figure 7

[2]

CPD

power dissipation

capacitance

per package;

VI = GND to VCC − 1.5 V

[3]

-76-

Table 7.

Dynamic characteristics

GND = 0 V; test circuit see Figure 8.

Symbol Parameter

Conditions

°C

−40 °C to +125 °C

Min

Typ

Max

(85

°C)

Max

(125

°C)

Unit

Measurement points are given in Table 8.

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

Fig 6.

Input (An, E3) to output (Yn) propagation delays and output transition times

001aag757

An, E3 input

Yn output

tTHL

tTLH

tPHL

tPLH

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