74LS191 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 74LS191 is synchronous, reversible up/down counters having a complexity of 58 equivalent gates.
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
191.pdf
74LS191 features
- Synchronous Up/Down Mudulo-16 Binary Counter, Count is Updated with Low-to-High Clock Transition
- Synchronous Counting
- High Speed up to 25MHz
- Individual Preset Inputs
- Standard TTL Switching Voltages
74LS191 pinout
| Pin | Name | Description |
|---|---|---|
| 1 | B | Data Input Of Counter B |
| 2 | QB | Output Of Counter QB |
| 3 | QA | Output Of Counter QA |
| 4 | CTEN' | Clock Enable |
| 5 | D/U' | Down/Up (Active Low) |
| 6 | QC | Output Of Counter QC |
| 7 | QD | Output Of Counter QD |
| 8 | GND | Ground |
| 9 | D | Data Input Of Counter D |
| 10 | C | Data Input Of Counter V |
| 11 | LOAD' | Load Pin (Active Low) |
| 12 | MAX/MIN | Maximum/Minimum |
| 13 | RCO' | Ripple Carry Output (Active Low) |
| 14 | CLK | Clock Pin |
| 15 | A | Data Input Of Counter A |
| 16 | VCC | Positive Supply |
74LS191 applications
- Frequency counters
- Digital clocks
- Analog to digital converters
- With some changes in their design, counters can be used as frequency divider circuits
- In time measurement
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