ADS1014-Q1: modular frequency and sampling rate configuration

Marvin Gasis Arcangel

Part Number: ADS1014-Q1
Other Parts Discussed in Thread: ADS1014, , ADS1114-Q1, ADS1015

Hi Team,

Can you please help with the question below?

On the datasheet Page 10/44

1. Why the 1-MHz internal oscillator has to be divided by the factor of 4? Is it because of the internal modulator was designed to run at a frequency of 250kHz. ?

2. If the modular frequency is 250KHz, according to Nyquist theorem which says 'a periodic signal must be sampled at more than twice the highest frequency component of the signal'. So in this case, the maximum frequency that could be sampled is Fmod/2 (250kHz/2) = 125KHz for ADS1014?

3. It is to be understood that there are several rates for data conversions such as 128 SPS, 250 SPS, 490 SPS, 920 SPS, 1600 SPS, 2400 SPS, or 3300 SPS. This can be configured by the given register in DR[2:0]. Configuring this will also change the Fmod rate at the input sampling.

4. According to Table 7.6 on page 22, Bit 7:5 Field DR[2:0] description says the binary bits for a maximum of 860 SPS only. How do we can set it for 3300 SPS and other SPS mentioned in Question 3?

Thank you.

Regards,

Marvin

over 1 year ago

0 Angel Rodriguez de San Miguel Bermudez over 1 year ago

TI__Expert 4750 points

Hi Marvin,

1. Yes, the internal modulator runs at a frequency of 250kHz.

2. That is correct, the highest frequency that can be sampled according to the Nyquist theorem is Fmod/2. Any frequencies higher than this would fold back and show up in the actual frequency band of interest below half the sampling frequency as an alias, which is why input filtering should be used to prevent unwanted higher frequencies to be wrongly captured.

3. No, the Fmod rate at the input sampling remains the same, what changes is the oversampling ratio (OSR) which is the (modulator clock/data rate) when different output data rates are selected.

4. Set bits DR[2:0] to 111 for a 3300SPS data rate, see table attached.

This table comes from the ADS1014 data sheet which is the correct table

ADS101x Ultra-Small, Low-Power, I2C-Compatible, 3.3-kSPS, 12-Bit ADCs With Internal Reference, Oscillator, and Programmable Comparator datasheet (Rev. E)

The ADS1014-Q1 data sheet used the DR[2:0] table for the ADS1114-Q1 which was a mistake we are working on getting fixed.

Best Regards,

Angel

0 Marvin Gasis Arcangel over 1 year ago in reply to Angel Rodriguez de San Miguel Bermudez

TI__Genius 9885 points

Hi Angel,

Thanks!

About question number 1, I have a follow-up. if let it be in 1MHz, What are the pros and cons of that design? Would be great if you could explain that in detail.

Thanks again.

Regards,

Marvin

0 Angel Rodriguez de San Miguel Bermudez over 1 year ago in reply to Marvin Gasis Arcangel

TI__Expert 4750 points

Hi Marvin,

The internal modulator frequency is 250kHz for this device, it is not a configurable parameter.

You can find out more about how delta-sigma ADCs work by watching out TI precision Labs series.

Analog-to-digital converters (ADCs) | TI.com

Refer to the 'SAR and delta-sigma: Basic operation' in the 'SAR and delta-sigma: Understanding the difference (4)' section for a detailed explanation.

Regards,

Angel

0 Marvin Gasis Arcangel over 1 year ago in reply to Angel Rodriguez de San Miguel Bermudez

TI__Genius 9885 points

Hi Angel,

Thank you.

I have another question, do we have an example/reference design for 4 to 20mA measurement using this device?

I looked at our reference library but I did not find any (or I may missed something). I wonder if you can share some

Thanks!

Regards,

Marvin

0 Angel Rodriguez de San Miguel Bermudez over 1 year ago in reply to Marvin Gasis Arcangel

TI__Expert 4750 points

Hi Marvin,

Available design and development resources for the ADS1014 can be found here ADS1014 data sheet, product information and support | TI.com

The EVM for the ADS1015 might be a useful tool ADS1015EVM-PDK Evaluation board | TI.com, the schematic for the EVM can be found at the end of the user's guide. The ADS1015 is the 4-channel version of the ADS1014.

Best Regards,

Angel

0 Marvin Gasis Arcangel over 1 year ago in reply to Angel Rodriguez de San Miguel Bermudez

TI__Genius 9885 points

Hi Angel,

I have a follow-up question about the input voltage protection. Referring to the 7.1 Absolute Maximum Rating where it says the input voltage should not be more than VDD + 0.3V otherwise it will cause permanent damage to the device. Now I want to know about the possible way it can get damaged.

For example, I have a temperature sensor with 0 - 5V, I can give a Voltage of 5V~5.5V to VDD from an external supply, right? if the sensor currently giving a 2.5V, and suddenly the VDD cable has been pulled out. In this situation, VDD is getting 0V or floating while Analog input lines have 2.5V. Will this cause damage to the device?

0 Angel Rodriguez de San Miguel Bermudez over 1 year ago in reply to Marvin Gasis Arcangel

TI__Expert 4750 points

Hi Marvin,

Yes, you can provide 5V-5.5V from an external power supply to VDD and it will work fine for your input range without causing any damage.

If you are applying a voltage to the input pins, and your VDD cable is disconnected, the device may be damaged since you would be violating the absolute max rating of VDD + 0.3 V since VDD would be at 0V and your input pin at 2.5V.

It is not a guarantee that the device will be damaged, but it is likely. The device should be operated within the recommended operating conditions to guarantee proper functionality.

Best Regards,

Angel

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ADS1014-Q1: modular frequency and sampling rate configuration