The CD74HC4051 is an 8-channel analog multiplexer: three select pins choose which of eight analog signals reaches one output, with about 70 Ω on-resistance at a 4.5 V supply and a switch voltage range of 0 to 10 V. It lets one ADC pin read up to eight sensors, such as a line-follower array. Figures are from the Texas Instruments CDx4HC405x datasheet SCHS122O.
Key specifications
| Channels | 8 (1 of 8 select) |
|---|---|
| Control voltage | 4.5–5.5 V |
| Switch voltage | 0–10 V |
| On-resistance | 70 Ω typ at 4.5 V |
| Switching | break-before-make |
| Temperature | −40 to 125 °C |
What the datasheet promises
| Item | Datasheet value |
|---|---|
| Function | Digitally controlled analog multiplexer and demultiplexer; the 4051 is the 8-channel member of the family |
| Control voltage | 4.5 to 5.5 V |
| Switch voltage | 0 to 10 V; analog input up to ±5 V with a split supply |
| On-resistance | 70 Ω typical at VCC − VEE = 4.5 V; 40 Ω typical at 9 V |
| Switching | Break-before-make, low crosstalk between switches |
| Direction | Bidirectional: any analog pin can be input or output |
| Enable | When high, all switches are off |
| Logic inputs | LSTTL compatible on the HCT parts; CMOS compatible |
| Temperature | −40 °C to +125 °C (CD74 parts) |
The 70 Ω on-resistance sets how it behaves with a high-impedance source: the ADC input sees the source resistance plus the switch, and a settling delay is needed after each channel change. If the voltage is changed and read too soon, the reading carries over from the previous channel.
Using it on a robot
- Tie the enable pin low and VEE to ground for a single supply; the signals must then stay between 0 V and the supply.
- Wait a short settling time after setting the select pins before sampling the ADC.
- Keep the logic supply within the 4.5 to 5.5 V control range; on a 3.3 V board check the HCT versus HC levels before connecting.
- For better resolution than the board’s own ADC, read the common output with the ADS1115.
Sources and further reading
- Texas Instruments CDx4HC405x analog multiplexer datasheet (SCHS122O) — the voltages, on-resistance and switching behaviour above.
Last reviewed: November 2026. Limits are from the Texas Instruments datasheet; breakout boards vary. No price is quoted because it has not been checked.
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