74LVC2T45GD datasheet(25/36 Pages) PHILIPS

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74LVC_LVCH2T45

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Product data sheet

Rev. 4 — 20 August 2010

25 of 36

NXP Semiconductors

74LVC2T45; 74LVCH2T45

Dual supply translating transceiver; 3-state

14.4 Enable times

Calculate the enable times for the 74LVC2T45; 74LVCH2T45 using the following

formulas:

• tPZH (DIR to A) = tPLZ (DIR to B) + tPLH (B to A)

• tPZL (DIR to A) = tPHZ (DIR to B) + tPHL (B to A)

• tPZH (DIR to B) = tPLZ (DIR to A) + tPLH (A to B)

• tPZL (DIR to B) = tPHZ (DIR to A) + tPHL (A to B)

In a bidirectional application, these enable times provide the maximum delay from the

time the DIR bit is switched until an output is expected. For example, if the 74LVC2T45;

74LVCH2T45 initially is transmitting from A to B, then the DIR bit is switched, the B port of

the device must be disabled before presenting it with an input. After the B port has been

disabled, an input signal applied to it appears on the corresponding A port after the

specified propagation delay.

74LVC2T45GD 数据表(PDF) 25 Page - NXP Semiconductors