HD74HC490
HD74HC490 is Dual 4-bit Decade Counters manufactured by Hitachi Semiconductor.
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 munication 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
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- High Speed Operation: tpd (Clock to QA) = 13 ns typ (CL = 50 p F) 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 Clear H L L Set-To-9 L H L Outputs QA L H Count QB L L QC L L QD L H
BCD Count Sequence
Outputs Count 0 1 2 3 4 5 6 7 8 9 QD L L L L L L L L H H QC L L L L H H H H L L QB L L H H L L H H L L QA L H L H L H L H L H
Pin Arrangement
1Clock 1Clear 1QA Output 1 Setto-9 1QB Outputs 1QC 1QD GND
1 2 3 4
CK CLR QA CLR QA
16 VCC 15 2Clock 14 2Clear 13 12
CK QB Set-to-9 QC
2QA Output 2 Setto-9
5 6 7 8
11 2QB 10 2QC 9 2QD Outputs
Set-to-9
(Top view)
DC Characteristics
Ta = 25°C Item Input voltage Symbol VIH Ta =
- 40 to +85°C Max
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- 0.5 1.35 1.8
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- 0.1 0.1 0.1 0.33 0.33 ±1.0 40 µA µA I OL = 4 m A I OL = 5.2 m A Vin = VCC or GND Vin = VCC or GND, Iout = 0 µA V I OH =
- 4 m A I OH =
- 5.2 m A Vin = VIH or VIL I OL = 20 µA V Vin = VIH or VIL I OH =
- 20 µA V Unit V Test Conditions
VCC (V) Min Typ Max Min 2.0 4.5 6.0 1.5
- 3.15
-...
