| ??? 11/26/08 10:58 Modified: 11/26/08 11:19 Read: times |
#160313 - I cannot see a differential mode Responding to: ???'s previous message |
Ap said:
The following datasheet says to wire internal ADC in differential mode. I cannot see a differential mode of ADC. You apply only unsymmetrical input signals to the ADC. Ap said:
If taking AGND as VRef- as common , is a Vref+ of 2.5V to 4.7V (at VDD=5V) still required or a signal of 0~5V ?. A Vdd of 5.12 as can be seen above is mandatory? As stated in the datasheet analog input voltage connected to micro must not be higher than Vref+ +0.3V. So, when powering the OPamp by AVdd, which is equal to Vdd, you should choose Vref+ = Vdd to avoid trouble! By the way, there's no need to connect Vref- and Vref+ explicitely to the micro. Have a look at figure 11-1 of datasheet. A hint: Ap, if you make changes to your schemes, please create for each change a new scheme and store it individually in your user page. Do not override older schemes, otherwise later visitors of this thread cannot understand what was going on. Also, store your scheme as gif-file and you can save lots of user page space. This will also result in a faster image buildup. Kai |
