DAC8565: Spike when power on

Shaofeng Luo

Part Number: DAC8565
Other Parts Discussed in Thread: DAC80504

Hi team

Customers are testing DAC8565 recently, but they found that each output would have a ~1.3V spike when powering on, lasting about several hundred us. Do you have any insight about this? We have no waveforms now due to the confidentiality.

over 4 years ago

0 Akhilesh K over 4 years ago

TI__Mastermind 19096 points

Hi,

Can you please post the waveform, without that its very difficult to suggest any solution. Any load connected to DAC outputs?

Also can you ask your customer, how are they powering up the DAC? Also whats the status of digital pins before power applied to DAC?

Most of the time, this behavior depends on the output stage circuit of the DAC. Unless I can see the waveform, I cannot judge whether this is due to the DAC's internal architecture creating this spike or external factors.

Regards,

0 Shaofeng Luo over 4 years ago in reply to Akhilesh K

TI__Intellectual 1680 points

Hi AK

Thanks for your quick reply, the waveform is as below, yellow is VCC, blue is VOUT, and there is no external circuit, just one 104 Cap for VCC. BTW, RSTSEL is pulled down to GND via 10kohm, it's low during powering on. So it's strange, could you help to test and see is it normal for this device? Thanks!

+1 Akhilesh K over 4 years ago in reply to Shaofeng Luo

TI__Mastermind 19096 points

Hi,

As I mentioned earlier, this is a typical glitch during power on in some of the DAC's due to the internal pre-charge output buffer not turned on. Precharge buffer is powered with VCC and it requires minimum threshold to turn on the output stage properly.

See below video to understand this effect and how we can mitigate using external circuits. Please note most of the newer generation DAC's doesn't have this behavior as it is taken care in the design itself.

https://training.ti.com/lessons-precision-dacs-power-glitch

Regards,

0 Shaofeng Luo over 4 years ago in reply to Akhilesh K

TI__Intellectual 1680 points

Hi AK

It's very clear, thanks! DAC80504 should be more suitable for new design, right?

0 Akhilesh K over 4 years ago in reply to Shaofeng Luo

TI__Mastermind 19096 points

Hi,

Yes, DAC80504 will be good choice here with very low power on glitch in the order of 40mV to 60mV.

Regards,

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DAC8565: Spike when power on