HD74ALVCH162721
3.3-V 20-bit Flip Flops with 3-state Outputs
ADE-205-184B (Z)
3rd. Edition
December 1999
Description
The HD74ALVCH162721's twenty flip flops are edge triggered D-type flip flops with qualified clock
storage. On the positive transition of the clock (CLK) input, the device provides true data at the Q outputs,
provided that the clock enable (
CLKEN) input is low. If CLKEN is high, no data is stored. A buffered
output enable (
OE) input can be used to place the twenty outputs in either a normal logic state (high or low
level) or a high impedance state. In the high impedance state, the outputs neither load nor drive the bus
lines significantly. The high impedance state and increased drive provide the capability to drive bus lines
without need for interface or pullup components. The output enable (
OE) input does not affect the internal
operation of the flip flops. Old data can be retained or new data can be entered while the outputs are in the
high impedance state. Active bus hold circuitry is provided to hold unused or floating data inputs at a valid
logic level. All outputs, which are designed to sink up to 12 mA, include 26
resistors to reduce
overshoot and undershoot.
Features
V
CC
= 2.3 V to 3.6 V
Typical V
OL
ground bounce < 0.8 V (@V
CC
= 3.3 V, Ta = 25
C)
Typical V
OH
undershoot > 2.0 V (@V
CC
= 3.3 V, Ta = 25
C)
High output current
12 mA (@V
CC
= 3.0 V)
Bus hold on data inputs eliminates the need for external pullup / pulldown resistors
All outputs have equivalent 26
series resistors, so no external resistors are required.
HD74ALVCH162721
4
Absolute Maximum Ratings
Item
Symbol
Ratings
Unit
Conditions
Supply voltage
V
CC
0.5 to 4.6
V
Input voltage
*1
V
I
0.5 to 4.6
V
Output voltage
*1, 2
V
O
0.5 to V
CC
+0.5
V
Input clamp current
I
IK
50
mA
V
I
< 0
Output clamp current
I
OK
50
mA
V
O
< 0 or V
O
> V
CC
Continuous output current
I
O
50
mA
V
O
= 0 to V
CC
V
CC
, GND current / pin
I
CC
or I
GND
100
mA
Maximum power dissipation
at Ta = 55
C (in still air)
*3
P
T
1
W
TSSOP
Storage temperature
Tstg
65 to 150
C
Notes:
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage
to the device. These are stress ratings only, and functional operation of the device at these or
any other conditions beyond those indicated under "recommended operating conditions" is not
implied. Exposure to absolute maximum rated conditions for extended periods may affect device
reliability.
1. The input and output negative voltage ratings may be exceeded if the input and output clamp
current ratings are observed.
2. This value is limited to 4.6 V maximum.
3. The maximum package power dissipation is calculated using a junction temperature of 150
C
and a board trace length of 750 mils.
Recommended Operating Conditions
Item
Symbol
Min
Max
Unit
Conditions
Supply voltage
V
CC
2.3
3.6
V
Input voltage
V
I
0
V
CC
V
Output voltage
V
O
0
V
CC
V
High level output current
I
OH
--
6
mA
V
CC
= 2.3 V
--
8
V
CC
= 2.7 V
--
12
V
CC
= 3.0 V
Low level output current
I
OL
--
6
mA
V
CC
= 2.3 V
--
8
V
CC
= 2.7 V
--
12
V
CC
= 3.0 V
Input transition rise or fall rate
t /
v
0
10
ns / V
Operating temperature
Ta
40
85
C
Note:
Unused control inputs must be held high or low to prevent them from floating.
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