ADS7066: data acquisition phase and necessity of input drive amplifier

Hello!

Thank you for posting on TI's E2E Forum!

Also thank you for referencing a the referring E2E post. To answer your questions: 

1. Yes, the acquisition phase will be extended so long as the CS remains low. If the throughput speed is not a priority then CS can be left low to extend the acquisition phases to fit the systems needs.  

2. Great follow up question! Technically yes, depending on the input source and if allowed enough time it could be done without an input amplifier.  We have this tech note going speaking about just this Optimizing Sensor Measurement: Driving a SAR ADC Input Without a Driver Amplifier. It goes through the calculations when the option to extend the acquisition phase (and slowing down sampling rate) in order to remove the need of an input driver amplifier.

If interested, you could share schematic and if any sampling speed limitations for review and I could make recommendations.

Best regards, 

Yolanda 

Hi, Yolanda!

Thank you for your reply.
I'm relieved to see that my understanding is correct.

Let me confirm something further.

If I extend the cycle time by changing the OSC_SEL and CLK_DIV[3:0] registers as shown in Table 7-3 of the datasheet, will the acquisition time be extended since the conversion time is fixed?

Best regards,

Hello!

I am glad to hear that its a relief! and I am happy to able to confirm your additional questions. 

Yes, when using the averaging module, the internal oscillator will be used to initiate all the conversions. Since the conversion time is independent of this, configuring OSC_SEL & CLK_DIV can be used to extend the acquisition phase of each cycle. 

t_cycle_osr - t_conv = t_acq

If I could ask, will all the channels of the ADS7066 be used to measure NTC thermistors, or is it just the one? 

Best regards, 

Yolanda 

Thank you for your response! Glad I could help

Best regards, 

Yolanda