74LS221 Dual Mono Multivibrator Schmitt Trigger
Package SOIC Series 74LS
74LS221 overview
The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. The 74LS221 device is a dual multivibrator with performance characteristics virtually identical to those of the ’121 devices. Each multivibrator features a negative-transition-triggered input and a positive-transition-triggered input, either of which can be used as an inhibit input.
Key specifications
Supply Voltage
4.75 - 5.25Vdc
Maximum Clock Frequency
40Mhz
Power Dissipation
2mW/gate @100kHz
Minimum Output Current
8mA
Propagation Delay
10nS
Fan Out (TTL Loads)
20
Datasheet
221.pdf
74LS221 features
- Dual, Highly Stable One-Shot
- Pinout Identical to 74LS123
- Hysteresis Inputs
- Direct Reset Terminated Output Pulse
- Standard TTL Switching Voltages
74LS221 pinout
| Pin | Name | Description |
|---|---|---|
| 1 | 1A | Input 1 Of Schmitt Trigger 1 |
| 2 | 1B | Input 2 Of Schmitt Trigger 1 |
| 3 | 1 CLR | Clear Pin 1 |
| 4 | 1Q | Output Of Schmitt Trigger 1 |
| 5 | 2Q | Output Of Schmitt Trigger 2 |
| 6 | 2 C(ext) | External Capacitor 2 |
| 7 | 2 R(ext)/C(ext) | External Capacitor/Resistor 2 |
| 8 | GND | Ground |
| 9 | 2A | Input 1 Of Schmitt Trigger 2 |
| 10 | 2B | Input 2 Of Schmitt Trigger 2 |
| 11 | 2 CLR | Clear Pin 2 |
| 12 | 2Q' | Invert Output Of Schmitt Trigger 2 |
| 13 | 1Q' | Invert Output Of Schmitt Trigger 1 |
| 14 | 1 C(ext) | External Capacitor 1 |
| 15 | 1 R(ext)/C(ext) | External Capacitor/Resistor 1 |
| 16 | VCC | Positive Supply |
74LS221 applications
- Increase the noise immunity in a circuit with only a single input threshold
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