HIT HD74HC490 Datasheet
HD74HC490
Dual 4-bit Decade Counters
Description
This circuit contains eight master-slave flip-flops and additional gating to implement two individual 4-bit
decade counters. Each decade counter has individual clock, clear and set-to-9 inputs. BCD count
sequences of any length up to divide-by-100 may be implemented with a single HD74HC490. Buffering
on each output is provided to ensure that suceptibility to collector communication is reduced significantly.
The counters have paralle outputs from each counter state so that submultiples of the input count frequency
are available for system timing signals.
Features
• High Speed Operation: tpd (Clock to QA) = 13 ns typ (CL = 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: VCC = 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
Function Table
Clear/Set-To-9
Inputs Outputs
Clear Set-To-9 Q
HLLLLL
LHHLLH
L L Count
A
Q
B
Q
C
Q
D
HD74HC490
BCD Count Sequence
Outputs
Count Q
D
Q
C
0L L L L
1L L L H
2L L H L
3L L H H
4L H L L
5L H L H
6L H H L
7L H H H
8H L L L
9H L L H
Pin Arrangement
Q
B
Q
A
1Clock
1Clear
1Q
Output
1 Set-
to-9
1Q
1QC
Outputs
1QD
GND
V
1
2
A
3
4
B
5
6
7
8
CLR
A
Q
CK
QB
QC
QD
Set-to-9
CLR
QA
CK
QB
QC
Set-to-9
QD
16
15
14
13
12
11
10
9
CC
2Clock
2Clear
A
2Q
Output
2 Setto-9
2Q
B
2QC
2QD
Outputs
(Top view)
2
HD74HC490
DC Characteristics
Ta = –40 to
Ta = 25°C
Item Symbol V
Input voltage V
IH
(V) Min Typ Max Min Max Unit Test Conditions
CC
2.0 1.5 — — 1.5 — V
4.5 3.15 — — 3.15 —
6.0 4.2 — — 4.2 —
V
IL
2.0 — — 0.5 — 0.5 V
4.5 — — 1.35 — 1.35
6.0 — — 1.8 — 1.8
Output voltage V
OH
2.0 1.9 2.0 — 1.9 — V Vin = VIH or VILIOH = –20 µA
4.5 4.4 4.5 — 4.4 —
6.0 5.9 6.0 — 5.9 —
4.5 4.18 — — 4.13 — IOH = –4 mA
6.0 5.68 — — 5.63 — IOH = –5.2 mA
V
OL
2.0 — 0.0 0.1 — 0.1 V Vin = VIH or VILIOL = 20 µA
4.5 — 0.0 0.1 — 0.1
6.0 — 0.0 0.1 — 0.1
4.5 — — 0.26 — 0.33 IOL = 4 mA
6.0 — — 0.26 — 0.33 IOL = 5.2 mA
Input current Iin 6.0 — — ±0.1 — ±1.0 µA Vin = VCC or GND
Quiescent supply
I
CC
6.0 — — 4.0 — 40 µA Vin = VCC or GND, Iout = 0 µA
current
+85°C
3
Loading...