CD74HC4067: CD74HC4067M96

Avaneesh Tripathi

Prodigy 10 points

Part Number: CD74HC4067
Other Parts Discussed in Thread: CD74HCT4067

Hi there,

I am using Part No. "CD74HC4067M96" in my circuit as per the suggested circuit dig.

where,

Pin 24 Is VCC_5V
Pin 1 Is MUX out
Pin 12 and Pin 15 Is Ground

MUX is working fine but sometimes whenever I switch on the circuit the circuit start heating and the IC temperature rises drastically but sometimes it works Normally without any heating.

Please suggest me the reason of this issue and Possible way to remove the same issue

over 3 years ago

0 Tyler McGuire over 3 years ago

TI__Expert 3515 points

Hi Avaneesh,

What voltage level are you using to drive the S pins? How much continuous current are you passing through the mux on the signal path?

The CD74HC4067 should never reach a junction temperature that is dangerous for the part if the datasheet is followed.

Thanks,
Tyler

0 Avaneesh Tripathi over 3 years ago in reply to Tyler McGuire

Prodigy 10 points

Hi Tyler,

We are using 3V3 Voltage level on S pins . Besides of VCC ,GND , and Select Line Pins all Pins are signal pins which are suppose to flow small signals having very Low Continuous Current

The main issue is sometimes it works perfectly without any heating but sometimes it gets Hot while turning on the Power (VCC_5V).

Please suggest me the cause of this fault and how to overcome from the same ?

0 Clemens Ladisch over 3 years ago in reply to Avaneesh Tripathi

Guru 316640 points

The input voltage must be above V_IH. In practice, the signal level should be identical with V_CC.

Input voltages between V_IL and V_IH indeed cause increased power consumption and potential damage; see [FAQ] How does a slow or floating input affect a CMOS device?

The CD74HCT4067 has TTL-compatible inputs that support 3.3 V signals.

How much current is flowing through the I/common pins?

0 Tyler McGuire over 3 years ago in reply to Avaneesh Tripathi

TI__Expert 3515 points

Hi Avaneesh,

The 3.3V used on the S pins is likely below the V_IH (between the 4.5V and 6V levels) and the device is heating up because of shoot-through current. This happens because both CMOS MOSEFTS are turned on allowing current to flow from VCC to ground. CD74HC4067 logic levels from datasheet:

The FAQ Clemens linked is a good resource as well as the application report: Preventing excess current consumption on analog switches

A solution would be to use the VCC voltage level (5V) on the S pins or select a device that has a lower V_IH like the CD74HCT4067:

Thanks,
Tyler

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CD74HC4067: CD74HC4067M96