• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 45 subscribers
  • Views 199 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS122C04EVM:EVMの測定結果について

Yoichi Taguchi
Prodigy 10 points
Part Number: ADS122C04EVM


ADS122C04EVMで(AVDD+AVSS)/2の設定で測定すると

チャネル: ADC0
サンプル:2048
平均: 17.9
標準開発: 22.3
パッケージ変換: 134
エノブ: 19.5
NFB: 16.9

の結果でした。 

データシートと違いがあります。

この結果は正しいですか、それとも異常ですか。

 もし異常だとしたら何が起きて居ると考えられますか。

教えてください。

スクリプトは以下の通りです。

This XML file does not appear to have any style information associated with it. The document tree is shown below.
 <script>
<name>Voltage Measurement Ain0-Ain1 short PGA:1 </name>
<description>This script uses the EVM voltage divider to measure voltages to 24V using the internal reference. Voltage is supplied to J6 pins 5(+) and 1(-). Measurement at AIN0/AVSS.</description>
<command_list>
<command>
<command_string>WREG 00 E0</command_string>
<description>Use the AIN0/AVSS input at PGA gain of 1 and PGA disabled</description>
</command>
<command>
<command_string>WREG 01 08</command_string>
<description>Use reference (AVDD-AVSS) at 20sps</description>
</command>
<command>
<command_string>WREG 02 00</command_string>
<description>Current sources off</description>
</command>
<command>
<command_string>WREG 03 00</command_string>
<description>IDAC routing disabled</description>
</command>
<command>
<command_string>REGMAP</command_string>
<description>Read back the register settings</description>
</command>
<command>
<command_string>DELAY 500</command_string>
<description>Delay to make sure register readback is complete</description>
</command>
</command_list>
</script>
  • 0
    TI__Guru** 113765 points

    Hi Yoichi Taguchi,

    Welcome to the E2E forum! The forum is English language only, so in the future please translate you questions in English first and then post.  You are actually using the wrong script.  To compare results you should be using the script called 'Basic Startup with Internal Reference, PGA Enabled and Shorted Inputs'.  The script you are using is for an external voltage measurement and an external reference.

    The result you are seeing is based on the selected voltage reference, the input voltage, data output rate and number of conversions.  The method of computation for the information given in the noise table is provided within the text of section 7.1 of the datasheet.  The number of conversions for each given data rate is not fixed but is computed by time to limit the effects of drift.  The period of collection is approximately 750ms.  The conversion time at 20sps data output rate is 50ms which would then be 15 samples instead of 2048 to be able to match the datasheet noise table.

    You also need to make sure that you are using the internal reference, and that the internal short is connected (AVDD-AVSS)/2.  The setup for this measurement is in the script I named earlier.

    If you want to modify a script, do not try to edit in an external program or editor.  Please use the script editor built into the GUI.

    Best regards,

    Bob B