Hello
My customer is currently having problems fully understanding the operation of SD24
They are reasonably comfortable with the SD16_A because they use it in current designs.
The SD24 of the MSP430I2040 is what they are having most trouble understanding.
Attached is a rough summary of some of what is puzzling to then, could you help answer these questions ?
2018-06-27 MSP430 Sigma-Delta Questions.xlsx
Thanks
Bob
Hello Bob,
Thanks for posting these questions to E2E.
Question 1: Does the above table mean you can apply negative voltages?
The MSP430i2040 has differential inputs, so yes, you can apply negative inputs (assuming they fall inside the absolute and common-mode input ranges shown in Table 5-21).
Question 2: Does +/-928mV mean the differential O/P can span 2 x 928mV = 1.856V? How is that achieved from the internal 1.2V reference?
Yes and no, although it really comes down to terminology. By "span" here, you're referring to the Full-Scale Range (FSR) for the specified performance (80% of max FSR). This is defined as the range of the differential inputs, not the difference between the inputs. For GAIN = 1, the difference between the inputs can range from +928mV down to -928mV. However, keep in mind that the absolute value of the difference never exceeds |928mV|. This is how the internal 1.2V reference can be used.
A simple example would be to put a book between your hands (difference) and swing your hands back and forth from left to right back to left (FSR).
Question 3: Is our interpretation for SD16_A correct?
I didn't look at the MSP430F2013, but for MSP430i2040, refer to Table 13-1 and Figure 13-7 in the User's Guide for more details about conversion modes and results.
I hope this helps.
Regards,
James
MSP Customer Applications
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