HD74AC HITACHI [Hitachi Semiconductor], HD74AC Datasheet - Page 19

• Manufacturer Part Number: HD74AC
• Description: HD74AC Series Common Information
• Manufacturer: HITACHI [Hitachi Semiconductor]

Definition of Specifications
1. Power Dissipation-Test Philosophy
In an erfort to reduce confusion about measuring C
has been adopted, which specifies the test setup for each type of device. This allows a device to be
exercised in a consistent manner for the purpose of specification comparison. All device measurements are
made with V
If the device is tested at a high enough frequency, the static supply current can be ignored. Thus at 1 MHz,
the following formula can be used to calculate C
18
Gates: Switch one input. Bias the remaining inputs such that the output switches.
Latches: Switch the Enable and D inputs such that the latch toggles.
Flip-Flops: Switch the clock pin while changing D (or bias J and K) such that the output (s) change each
Decoders: Switch one address pin which changes two outputs.
Multiplexers: Switch one address pin with the corresponding data inputs at opposite logic levels so that
Counters: Switch the clock pin with other inputs biased such that the device counts.
Shift Registers: Switch the clock pin with other inputs biased such that the device counts.
Transceivers: Switch one data input. For bidirectional devices enable only one direction.
Parity Generator: Switch one input.
Priority Encoders: Switch the lowest priority input.
Load Capacitance: Each output which is switching should be loaded with the standard 50 pF. The
C
PD
= I
CC
clock cycle. For parts with a common clock, exercise only one flip - flop.
CC
= 5.0 V at 25 C, with 3-state outputs both enabled and disabled.
/ (V
the output switches.
CC
) (1
equivalent load capacitance, based upon the number of outputs switching and their
respective frequency, is then subtracted form the measured gross C
obtain the device’s actual C
) – Equivalent Load Capacitance
Definition of Specifications
PD
PD
:
PD
, a JEDEC standard test procedure (7A Appendix E)
value.
PD
number to