CD4015B: Not getting the expected outputs for the given Clock and Data inputs

Santhosh Kumar S

Part Number: CD4015B

Hello Everyone.

I'm using CD4015B Shift register in my design as shown in the attached image. Pin 9 is connected to 1MHz clock. For data input, we are giving inverted signal of the Q4.

We are expecting a 250kHz pulses in each outputs Q1, Q2, Q3 & Q4. But we dont see an expected outputs signals.

We are getting all outputs as 1V DC.

I have also connected 4.7K Pullup at the Data input pin and tried it (thinking at the initial point the input will be floating and hence I'm not getting the output). But still the outputs are same.

Can anyone please look at my design and help me if there are any problem in the design or suggest me what all I can do to rectify this issue.

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316690 points

All unused inputs of CMOS devices must have a valid logic level, i.e., VCC or GND.

Is there any load on the outputs? They should be at 0 V, unless there is a pull-up.

0 Santhosh Kumar S over 1 year ago in reply to Clemens Ladisch

Prodigy 200 points

1. Yes unused inputs are connected like below image.

2. Yes. Each outputs are connected to pin no. 16 of Four different ICs i.e. UCC28950PW.

0 Clemens Ladisch over 1 year ago in reply to Santhosh Kumar S

Guru 316690 points

The outputs should driver either high or low. I cannot explain why there would be 1 V. How exactly are you measuring this?

Please check that the supply pins have the correct voltage. Try another chip.

0 Santhosh Kumar S over 1 year ago in reply to Clemens Ladisch

Prodigy 200 points

Does the device expects pull up to vcc at the data input pin? (Anyway, we tried that also even though we don't have pullup in the design, we connected 4.7k pullup to Vcc and checked the output)

I'm measuring using the oscilloscope probe pointing directly at the output pins with respect to AGND.

We also verified the voltage at the supply pin it is 5V. Also, the clock at the CLK pin it is 1MHz.

Not sure what else I can do. May be I have to try another chip as you told.

Regards,

Santhosh

+1 Malcolm Lyn over 1 year ago in reply to Santhosh Kumar S

TI__Mastermind 26010 points

Hi Santhosh,

I'd try another chip to see if you replicate the result or if the chip currently being used is just damaged.

Best,

Malcolm

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CD4015B: Not getting the expected outputs for the given Clock and Data inputs