The 7490, is a 4-bit decade counter IC from the 74xx TTL series. It consists of a divide-by-two and a divide-by-five counter, allowing it to count from 0 to 9 in binary (mod-10). It features asynchronous clear and preset inputs for control. Commonly used in digital clocks, frequency counters, and timers, it outputs binary-coded decimal (BCD) values.
| Number of Stages | 4 |
|---|---|
| Supply Voltage | 2V to 6V |
| Max Output Current | ±25 mA |
| Propagation Delay | ~22 ns |
| Operating Temperature | -40°C to +85°C |
📄 SN74HC90N datasheet (1311 kB)
| Pin Number | Name | Description |
|---|---|---|
| 1 | CLKB | Clock Input B (for divide-by-5 stage) |
| 2 | R0(1) | Reset Input 1 (sets counter to 0 when both R0(1) and R0(2) are high) |
| 3 | R0(2) | Reset Input 2 (sets counter to 0 when both R0(1) and R0(2) are high) |
| 4 | R9(1) | Reset Input 1 (sets counter to 9 when both R9(1) and R9(2) are high) |
| 5 | R9(2) | Reset Input 2 (sets counter to 9 when both R9(1) and R9(2) are high) |
| 6 | NC | No Connection |
| 7 | GND | Ground |
| 8 | QD | BCD Output D (2³, weight 8) |
| 9 | QC | BCD Output C (2², weight 4) |
| 10 | QB | BCD Output B (2¹, weight 2) |
| 11 | QA | BCD Output A (2⁰, weight 1) |
| 12 | CLKA | Clock Input A (for divide-by-2 stage) |
| 13 | NC | No Connection |
| 14 | VCC | Supply Voltage |