BCD Counter 7490

The BCD Counter 7490 is a 74-series decade counter IC that counts clock pulses from 0 to 9 and gives the count in binary-coded decimal (BCD) on four outputs. Inside it has a divide-by-2 and a divide-by-5 section, which you link to count to 10, plus inputs to reset the count to 0 or set it to 9. It is a classic chip for digital electronics labs, counters and clocks.

BCD Counter 7490 Specifications

• Function: decade (divide-by-10) counter with BCD outputs QA–QD
• Internal stages: divide-by-2 (input A, output QA) and divide-by-5 (input B, outputs QB–QD)
• Control inputs: two reset-to-0 inputs R0(1), R0(2) and two set-to-9 inputs R9(1), R9(2)
• Clock: counts on the falling (high-to-low) edge
• Package: 14-pin DIP, through-hole
• Supply: 5 V, VCC on pin 5 and GND on pin 10

BCD Counter 7490 Applications

• Digital counters and frequency dividers (÷2, ÷5 and ÷10)
• Driving 7-segment displays through a BCD decoder such as the 7447 or 7448
• Digital clocks, timers and event counters
• Logic and digital electronics lab experiments

What's in the Box

• 1 × 7490 BCD decade counter IC

Tip: For a normal 0–9 BCD count, connect output QA (pin 12) to input B (pin 1) and feed the clock into input A (pin 14). Note the unusual power pins: VCC is pin 5 and GND is pin 10, not the corner pins used by most 74-series chips. Tie the reset and set-to-9 inputs to GND so the counter runs.

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