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# CD4051B-Q1: Capability for Full rail operation

Part Number: CD4051B-Q1
Other Parts Discussed in Thread: CD4051B

Hi Team,

I want to know if CD4051B-Q1 can deal with rail to rail signal(0~5V signal) under following condition or not.
I'm expecting that I can get we can get same voltage level signal from CD4051B's output.

VDD = 5V
VEE = VSS = 0V
Signal range : 0~5V

Do you have any data or equation to estimate how much drop will be appeared at output side?

The Datasheet says as below, so I believe the signal level is almost same(some drop might exist due to Ron and though current)

>The analog signal (through the TG) may swing from VEE to VDD

Regards,

Takashi Onawa

• Takashi-san,

The CD4051B-Q1 datasheet recommended supply voltage range can be 5V.  This device is a transmission gate FET switch so that means it has an NFET in parallel with a PET so it will have rail to rail operation and support signal voltages 0 to Vdd.

The voltage drop across the switch in a DC application will be due to the on-state resistance Ron.  At Vdd = 5V, typically the Ron is 470 ohms.  The equation to calculate the voltage drop with be the current passing through the switch times the on-state resistance.  As you can see below the on-state resistance will vary with temperature and input voltage.

Thank you,

Thanks for your prompt response on this.

OK, I understood it can work as rail to rail. And Ron has some temperature and voltage dependency as above.

One quick question.
What kind of issue will come out if VDD voltage drops 5% from the 5V?
The Min recommendation rage is 5V as you mentioned above, but the power supply might be varied +/-5% due to load condition.

Regards,
Takashi Onawa
• Takashi-san,

We cannot recommend using the device outside the recommended operating conditions.

As VDD decreases on-state resistance increases as you can see in the Ron chart below.

Thank you,