SN74AUC2G04: Dual LED Drive using SN74AUC2G04 inverter

Deepak c

Prodigy 100 points

Part Number: SN74AUC2G04
Other Parts Discussed in Thread: SN74AUP2G17, SN74LVC2G34, SN74LVC2G04

Hi,

I am using 2 Pin Bicolor LED where reversing polarity change its color.

Supply Voltage :3.3V

LED Specifications are

Forward Voltage: 2V

Max Current: 20mA

Can we use Dual inverter gate (SN74AUC2G04) for driving LED?

Datasheet Link:

https://www.ti.com/lit/ds/symlink/sn74auc2g04.pdf?HQS=dis-mous-null-mousermode-dsf-pf-null-wwe&ts=1658745537682&ref_url=https%253A%252F%252Fwww.mouser.in%252F

I have made configurations like below.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 278110 points

AUC devices are not designed for 3.3 V. Use a family like AUP or LVC.

You can use either inverters (74xx2G04, 74xx2G14) or plain buffers (74xx2G17, 74xx2G34).

Without a separate resistor, the current is limited only by the output impedance of the gate itself. AUP devices (e.g., SN74AUP2G17) have about 50 Ω, for a total resistance of about 100 Ω when going through two gates, with a resulting current of about 10 mA. LVC devices are too strong and always need a current-limiting resistor.

0 Deepak c over 2 years ago in reply to Clemens Ladisch

Prodigy 100 points

Hi Clemens,

Thanks for suggestions.

Based on availability, i have found SN74LVC2G34 which has good output current.

Can you please help how did i know output impedance? I am not getting in Datasheet.

Also, LED module has inbuilt resistor.

Also there is a statement that "Supports 5V VCC Operation" but i have 3.3V supply, can i still use this series?

0 Deepak c over 2 years ago in reply to Deepak c

Prodigy 100 points

I have checked my Library where we have readymade footprint of SN74LVC2G04DBVR

Can we use this as well? Also please help me with Series resistor for this?

0 Clemens Ladisch over 2 years ago in reply to Deepak c

Guru 278110 points

See [FAQ] What is the output voltage (VOH or VOL) when the output current is X or the supply voltage is Y?

The statement that 5 V is supported does not rule out support for other voltages.

As mentioned above, an inverter in the LVC family will work.

If the LED module has a built-in resistor, then it is likely that you do not need an external one. But I cannot be specific without seeing the datasheet.

0 Deepak c over 2 years ago in reply to Clemens Ladisch

Prodigy 100 points

Hi Clemens,

Please find attached datasheet

https://www.mouser.in/datasheet/2/26/Apem_09152017_QS-1158415.pdf

Can you please confirm now?

0 Sebastian Muriel over 2 years ago in reply to Deepak c

TI__Genius 14910 points

Hi Deepak,

Deepak c said:
Can you please help how did i know output impedance? I am not getting in Datasheet.

You can calculate the output impedance from the electrical characteristics table.

For example at a Vcc of 3V:

Rout = (Vcc- VOH)/IOH= 3V - 2.4V / 16mA = 37.5 Ohms

Deepak c said:
Also there is a statement that "Supports 5V VCC Operation" but i have 3.3V supply, can i still use this series?

Yes you can still use these devices, they support a supply voltage from 1.65V to 5.5V.

Deepak c said:
Can we use this as well? Also please help me with Series resistor for this?

You could use the SN74LVC2G04 or the SN74LVC2G34.

I don't see any mention of an internal resistor in the datasheet you attached, I would suggest using a series resistor of 150Ohms at the output of our device to keep the current below 20mA.

Regards,

Sebastian

0 Clemens Ladisch over 2 years ago in reply to Deepak c

Guru 278110 points

The model that you have marked does not have a built-in resistor.

A resistor of 68 Ω, 100 Ω, or 150 Ω would result in a reasonable current.

0 Deepak c over 2 years ago in reply to Sebastian Muriel

Prodigy 100 points

Hi Sebastian,

Thanks for details.

For resistors- If we want to operate 2-3.3VDC, then Then current limiting resistor is not required as they have internal resistors.

Also, Based on my understanding i have drafted drive for LED.

Can you please confirm it is correct?

0 Clemens Ladisch over 2 years ago in reply to Deepak c

Guru 278110 points

This circuit is correct.

The QS10xYYRG02 devices have no internal resistor.

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SN74AUC2G04: Dual LED Drive using SN74AUC2G04 inverter