CD4051B:Current supported by switching channels

user4531622

Part Number: CD4051B
Other Parts Discussed in Thread: MUX508, SN74CBT3251, TCA6408A, TCA6507

Hello,

Do I need to know the current supported by the channels of the integrated circuit CD4051B? Because I couldn't identify it in the data sheet.

My thanks, to whom I help.

over 6 years ago

0 Fan.Wang over 6 years ago

TI__Intellectual 2900 points

Hello,

Are you looking for how much continuous current CD4051 can conduct? Even 10mA will be too high across temperature

0 user4531622 over 6 years ago in reply to Fan.Wang

Prodigy 80 points

Thanks for the rapid response Fan. Wang.

For normal operating conditions (25 º C/+ 5v), does the channel current remain low of 10mA?

0 Fan.Wang over 6 years ago in reply to user4531622

TI__Intellectual 2900 points

Hello,

For normal operating condition, the channel current, from CH0 to COM for example, should be lower than 10mA and this requirement should be guranteed by your design.

If you can post your tentative schematic and explain what you would like to achive, we can quickly help you review if CD4051B is the best fit :-)

0 user4531622 over 6 years ago in reply to Fan.Wang

Prodigy 80 points

I have to perform the scan of 3 displays "FYQ-3641AS", but I would like to reduce the number of pins used by the microcontroller. However, the available space for PCI is small.

0 Fan.Wang over 6 years ago in reply to user4531622

TI__Intellectual 2900 points

Thanks for the system information.

Do you think MUX508 can also serve your request? And it has higher current conducting rating.

0 user4531622 over 6 years ago in reply to Fan.Wang

Prodigy 80 points

Ola,
Segue o circuito que estou trabalhando.

0 user4531622 over 6 years ago in reply to user4531622

Prodigy 80 points

In this circuit, I performed the test with all one-digit segments permanently connected, where current consumption reached 70mA. In this case will overload the MUX508?

0 Fan.Wang over 6 years ago in reply to user4531622

TI__Intellectual 2900 points

Hello,

Do you mean 70mA per channel? To me, a simple LED segment like yours is normally around 15mA.

0 user4531622 over 6 years ago in reply to Fan.Wang

Prodigy 80 points

Hello,
Yes, each segment consumes 15mA.
However, I want to insert the multiplexer into the common pin of each digit of the monitors (reducing the number of microcontroller pins), in this way the possibility of energizing the 7 segments plus the decimal point is valid. Thus, it can consume 120mA if 15mA per segment.

I found the ci 74CBT3251, which supports 128mA per channel. It should work, right?

0 Fan.Wang over 6 years ago in reply to user4531622

TI__Intellectual 2900 points

Hello,

SN74CBT3251 is an 8:1 multiplexer. It will never allow you to energize 7 segments.

In your case, I would use TCA6408A or TCA6507. Both have I2C interface and it can save your microcontroller IO.

If your LEDs are just on and off, TCA6408A is easy. If you want to use PWM control LED intensity and some fancy dimming feature, TCA6507 is the right one.

0 user4531622 over 6 years ago in reply to Fan.Wang

Prodigy 80 points

Hello,
Fan Wang please could you please explain to me why the SN74CBT3251 CI is not fit for my application?
According to the scheme that I put, connecting this IC to the common pins of each display, the current for each channel would reach 120mA, where the SN74CBT3251 CI allows up to 128mA per channel.

0 Fan.Wang over 6 years ago in reply to user4531622

TI__Intellectual 2900 points

Hello,

SN74CBT3251 datasheet can handle 128mA continuous current at 25C without permanently damging the device. I am assuming your application might require temperature much higher than 25C. maybe 55C?

In addition, 8 LED segments consume 15mA (typical) * 8 = 120mA. In other words, only 6.7% ((128mA - 8mA)/120mA) variation is allowed, whose margin is very tight to me.

Please feel free to correct me if any of my assumptions are not valid in your system.

0 user4531622 over 6 years ago in reply to Fan.Wang

Prodigy 80 points

Hello.
Thanks for the reply Fan Wang.
I understand your concern and it really is possible to raise the temperature to 55 ° C. I will re-evaluate the project with the above mentioned CIs.

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CD4051B:Current supported by switching channels