ADS8584S: Power consumption at frequencies lower than 330kSPS

Hi Magda,

The datasheet only specifies the typical and maximum current at the highest throughput, we do not have the curve/data of power consumption at 20ksps sampling rate. However, I can measure the AVDD current on the ADS8588SEVM which is 8-channel and 200ksps version, you can compare the measured IAVDD at 20ksps with the IAVDD at 200ksps. If I can find an ADS8548S sample, I will check ADS8548S for you. Let me know if this is good solution for you. Thanks.

Best regards,

Dale

Hi Dale, 

Thank you for your reply. 

Ideally an ADS8584S would be the best to do the measurement. Otherwise, could you sample just 4 channels on the ADS8588SEVM board rather than all 8? 

Best,

Magda

Hi Magda,

I can disconnect one CONVST signal from the controller card and just use one of CONVST signals for 4-channel operation, however I will have to find an ADS8588S sample and get my colleague's help to solder it to an empty EVM board because I do not have an existing EVM for a test. Another solution may be the best solution, I will request ADS8584S sample and then solder it to an empty EVM directly for this test. The measurement will be accurate because this is the device you want to use, however it will probably take a week to get new ADS8584S sample. Let me know if you would wait for that. 

Best regards,

Dale

Either will work, Dale. I need a good estimate, not a precise figure. Thank you very much for your help!

Magda

Hi Magda,

I will get it back to you late next week after the holiday. Thanks.

Best regards,

Dale

Hi Magda,

Please see the test result (IAVDD) in the following table, thanks for your patience.

Best regards,

Dale

Hi Dale,

Many thanks for your reply and data. 

I'm a bit puzzled though. According to the datasheet, at 330kSPS the typical current is 10.9mA, applying VDD=5 V, (external reference), This would correspond to 54.5mw, as listed in the data sheet. You measured 13.4mA at 20kSPS.or 23% higher. Why would this be? If at all I'd expect about the same, if VDD is independent of sampling frequency. I need to think more about this.

Thank you again,

Magda

Hi Magda,

The ADC I measured is ADS8588S, there is no way to completely disable the 4 channels on the ADS8588S, so the CONVSTB was disconnected in the test and actually the last 4 channels on the ADC are still active in static status. The ADS8584S only has 4 channels and there is no any other active channel on the ADC, and this is the reason why you see 10.9mA typical on ADS8584S vs. 17.7mA typ on ADS8588S IAVDD at highest throughput. My test result can only give you an idea that the measured IAVDD matches the specifications in the datasheet, and also how much lower IAVDD at 20ksps vs. 200ksps on the same ADC.

If you really want to check ADS8584S at 20ksps throughput, please let me know and we have to wait for the sample.

Best regards,

Dale

Hi Dale, 

Thank you again for your prompt reply and info. I see your point. No need to check further the ADS8584S, I see now that a lower sampling frequency will not drastically reduce the power consumption since the analog current and voltage are the major contributors. I'm looking for lower power ADCs with PGA. My signal is under 5V amplitude. Any recommendations?

Best,

Magda

Hi Magda,

Most SAR ADCs do not have an internal PGA. I have few questions for you which can help me narrow it down.

1. Do you consider a delta-sigma ADC?
2. Is simultaneous-sampling ADC required?
3. Based on your information, you are looking for single-ended input and 0-5V range, and also 20ksps/ch 4-ch ADC. Please correct me if my understanding is incorrect.

Thanks.

Best regards,

Dale

Hi Dale,

Thank you for your reply.

I'm still waiting for some answers from my client, but here is what I have for now as far as requirements

1. 8 channel ADC - sampling rate per channel: 200 kHz

2. a 4 channel ADC  - sampling rate  per channel: 20kHz

3. single-ended input

4. minimum 16 bit data resolution

5. either SAR or delta-sigma should work 

6. PGA 

Need final confirmation for: 

a.. simultaneous sampling

8. analog input range (-5V, 5V)

Low power consumption is very important.

Best,

Magda

Hi Dale, 

Here are the requirements

1. One 8 channel ADC - sampling rate per channel: 200 kHz

2. One 4 channel ADC  - sampling rate  per channel: 20kHz

3. Single-ended inputs for all

4. Minimum 16-bit data resolution

5. Either SAR or delta-sigma should work 

6. PGA 

7. Simultaneous sampling

8. Analog input range (-5V, 5V)

9. SPI or I2C protocol - both OK.

Low power consumption is critical.

Best,

Magda

Hi Magda,

Our simultaneous-sampling Delta-sigma ADCs(e.g. ADS131M08) can support your 20kHz data rate and all other requirements, but it can not support +/-5V.  Also, we do not have a simultaneous-sampling Delta-sigma ADC to support 200ksps/ch. Please see this link for 8-ch simultaneous-sampling delta-sigma ADC.

Our HV SAR ADCs including ADS8588S/8584S meet your all requirements, only except  power consumption. What's your power consumption or supply current requirement?

Thanks&regards,

Dale

Thank you for the info, Dale. The combined  ADCs should ideally consume no more than 100mW, but the other features prevail. I guess for now I will stick with ADS8588S/8584S.

Best,

Magda

Hi Magda,

Thanks for your feedback, let me know if you need any further support and have any questions,

Regards,

Dale