ywguo wrote on Jun 14th, 2013, 8:47am:Hi Saket,
Why do you worry about glitches? That is a discrete-time system.
How is the non-ideality introduced in the ΔV
BE equation?
If there is big interference in your system, you need anti-aliasing filter. I don't know whether there was anti-aliasing filter in Tuthill's work because he didn't mention it.
Quote:Is this the reason why Sigma-Delta Modulators are used in Temperature Sensors? Can SAR ADCs be used instead?
I don't understand your question. That author did use SAR ADC instead of ΣΔ modulator for his temperature sensor.
Best Regards,
Yawei
Hi Yawei, thanks for your response. For a while I thought I wasn't going to get any
The reason I worry about glitches is if I decide to use an SAR ADC. Glitches at the output could lead to erroneous results, although it can be argued that if enough time is given for the output to settle, it should be ok.
More worrisome is the absence of an anti-aliasing filter. The wideband thermal noise will alias back in sampled data systems. Given that ∆Vbe increases by only 200-300uV per degree Kelvin, this noise could be an issue. That is why I asked about the need for anti-aliasing filters.
The non-ideality is introduced when an offset voltage is subtracted from the amplified ∆Vbe. Since the offset voltage comes from the bandgap, the amplified output will contain the bandgap error.
Finally, I wanted some comments on the use of the ADC. Usually a ΣΔ ADC is used in temperature sensors. Tuthill's paper mentions an SAR ADC. What is the advantage that a ΣΔ ADC has over other architectures? Why is it the preferred choice for temperature sensors?
Also, on a related note, are there any continuous time implementations for a ΔVbe based Temperature sensor? Put another way, can the noise and bandgap errors be within limits to get a ±2 degrees precision?