Hi sir
May I ask the internal AD conversion analog voltage input range of MSP430F4793 whether the Vfsr value reference is relative to AVSS or 1/2vcc?
Hi,
please see the details on the input range specification in the device datasheet. For your convenience I am pasting the table in here.
Furthermore you can find as well in the datasheet the specification for the built-in reference voltage source and the range in case of use of an external reference. Please consider also the device's User's Guide for further details on the SD16 operation.
Best regards
Peter
Hi Peter,
1、What I want to confirm is the relationship between A1.5, A1.6 and Vs+ and Vs-.
2、What reference voltage is ± 0.6v of ±Vfsr based on?
3、What is the logical relationship between Vs+, Vs- and AVcc/2? What is the range of Vs+ Vs-?Can we set Vs+ to 1.8v and Vs- to 0V?
Hi Peter，
1、I would like to know the guidelines of Vs+ and Vs- set by A1.5 and A1.6. Please inform me. Thank you
2、Does ±Vfsr=± 0.6v mean that the maximum differential pressure is 0.6v based on the reference voltage? So what's the reference voltage?
3、What is the logical relationship between Vs+, Vs- and AVcc/2?Is it feasible to set Vs+ to 1.8v and Vs- to 0V? If not, please let us know why. Thank you
Hi,
many thanks for the further clarification of your questions. I think you have to be careful not mixing here different things with one another.
to your 1st question:
From the user's perspective there is not much to care about +Vs and -Vs with the inputs A1.5-A1.7. As described in the User's Guide, these are all internal signal sources for the ADC. A1.5 is connected to an integrated resistive voltage divider, which gives you the possibility to measure the device supply voltage without any additional external components. If the device is supplied from a battery without an LDO, this means you can measure the battery voltage. A1.6 is connected to the internal temperature sensor, which allows you to measure the chip temperature. Due to the low power consumption and thus low heating up of the device itself, it is usually very close to the ambience temperature. Finally A1.7 is a short on the positive and negative input. This allows you to measure the offset of the PGA, as in ideal case the result should be 0.
to your 2nd question:
As described in the section of the User's Guide, which you pasted in, in this very section right about the formula for the calculation of the Vfsr you can see the example is based on the built in reference of 1.2V
to your 3rd question:
As in my original post and the datasheet specification of the applicable input voltage ranges, the input voltage is dependent on the following factors:
a) Used voltage reference. This can be either the built in reference. In this case typ. 1.2V, or an external reference, which can be, as specified in the datasheet 1.5V max.
b) Selected Gain of the PGA.
c) ADC mode selection Bipolar mode or Unipolar mode.
As according to the formula +Vfsr = (1.5V/2)/1 = 0.75V, plus as described in the UG and datasheet, the input voltage should not exceed 80% of the maximum applicable voltage, you'll never be able to apply 1.8V directly.
Best regards
Peter
Hi peter,
Thanks very much！
My new question is:
Standard and method of MSP430F4793 ADC interface borrowing signal and reference voltage.
For example 1: I connect 3.6v reference voltage to A0.0+, and A0.0- connect signal (2~3V) to test the temperature, is it feasible? Or what are the criteria for an ADC's plus or minus interface?
For example 2: I connect A1.0+ to signal (2~3V), A1.0- connect to AVss reference voltage to detect voltage, is it feasible? Or what are the criteria for an ADC's plus or minus interface?
Looking forward to your reply. Thank you
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