SN74HC4060-Q1: low temperature fault

Hi,

This is what I am understanding on the working of this device.

You are using the HC4060 which is a binary counter with an OR gate which will always output a high once the yellow signal or pin 1 of the or gate goes high.

You are seeing the yellow signal pulse if the power to both devices is quickly turned on or off is that correct?

Are the remainder of the pins of HC4060 unused?

What does pin 11 the clock input of HC4060 connect to? Can you provide a scope shot of this signal as well when the error occurs? The falling edge on pin 11 causes the binary counter to increment. I don't need to see the green signal as the LVC1G32 is operating correctly, when the yellow signal goes high.

Another thing to note is that your rising edges are very slow and unhealthy for the device as well as cause massive current consumption. The datasheet specs a rising edge that is at least 1us when the Vcc is 2V.

Thanks!

-Karan

Hi Karan,

Sorry, before the information I described is a little wrong. I will describe it again and also add the information that you asked.

The following problems were found during the test.(Yellow: power, Green: 4 pin, Blue: 5 pin, Pink: 7 pin)

1.When the temperature is -40 °C, the low-voltage power-on and power-off test is performed.

> When the power is off after a long time (about 20s or longer) and then power on, the measured waveform is shown in Figure 1. No collision will be reported.

> When the power-off time is short (at this time power supply voltage has reduced to 0) and then power on, the measured waveform is shown in Figure 2. When the collision fault is reported, you can see that the input of IC3903 has a spike and the voltage is about 1.6V - 1.8V, the output of IC3903 is high, as shown in Figure 2;

2.  When the temperature is adjusted to 25 ° C, the test waveform is shown in Figure 3.

4.The pin11 is connected to the 32.76kHz crystal oscillator. The waveform is as follows: yellow is the chip power supply, green is the counter 4 pin, blue is the counter 5 pin, pink is the counter 11 pin.

Thanks & Best Regards,

Sherry

Karan,

Sherry has update issue description. Please look into this issue. There is one voltage pulse at SN74HC4060-Q1 pin5 output at -40C. Customer has checked that when temperature is 25C and -10C, there is no voltage pulse at pin5 output.

This issue seems something related with device temperature, pin5 will output a pulse at -40C. We checked the device return record, no issue is reported.

Could you do some analysis for the output structure and possible reason to cause this? The project is close to SOP, please help on this.

Thanks.

Johnny

Hi Sherry,

This is what I believe is happening. The device is powering up very slowly. So when Vcc is about 1V, the switching threshold is at 500mV. This means that those small oscillations at the clock input might be causing the counter to increment. The clock input is not disabled because your clear pin is low during this whole time. Then when the clear pin jumps high, the outpus will go low. It is not the device but I believe your crystal oscillator that is becoming noisier at the low temperature. Can you provide a scope shot of the counter 11 pin when operation is normal and incorrect again but zoomed at the incident point so we can see the noise? And my assumption is when you wait a long period of time it allows the crystal oscillator time to turn off. (I don't have too much knowledge on crystal oscillators).

Here is what I see:

The solution would be to make sure CLR pin stays high and doesn't go low as it visibly does in those scope shots, or to make sure your CLK input pin is low or grounded at startup.

Thanks!

-Karan

Hi Karan,

our device's working voltage range is 2-6V. When the fault occurs, the voltage is 1V, our device can't work normally, right?

Thanks & Best Regards,

Sherry

Hi Sherry,

Any Updates?

Thanks!

-Karan

Hi Karan,

The customer's schematic is as below. The clear pin will be pulled up once power up, but the power UAUX has a rise time as the second picture.

This fault occurs around 1V which is outside of the normal voltage range, but the fault is related to the temperature. Because the fault doesn't occur when the temperature is 25℃ or higher. Do you have any idea about why the fault occurs at the negative temperature?

Thanks & Best Regards,

Sherry

Hi Karan,

I will send to you the email.

Thanks & Best Regards,

Sherry