Kinetis KL2x ADC参考电源（已解决）

只看该作者 · 2014-5-28 21:58

本帖最后由 FSL_TICS_A 于 2014-6-3 16:32 编辑

规格书478页上说明可以有两种选择：
Selectable voltage reference: external or alternate。

480页简单的描述了一下。
28.2.3 Voltage Reference Select
..... 概括来说就是此芯片可以选择两种模式VREFH and VREFL / VALTH and VALTL ,
通过ADCx_SC2寄存器来选择......

492页：通过ADCx_SC2寄存器来选择
28.3.6 Status and Control Register 2 (ADCx_SC2)
Voltage Reference Selection
Selects the voltage reference source used for conversions.
00 Default voltage reference pin pair, that is, external pins VREFH and VREFL

01 Alternate reference pair, that is, VALTH and VALTL . This pair may be additional external pins or
internal sources depending on the MCU configuration. See the chip configuration information for
details specific to this MCU

外部参考源external pins VREFH and VREFL大家都知道。
但是Alternate reference pair, that is, VALTH and VALTL 呢？规格书说与芯片配置有关，如何配置呢？
整个规格书都没有说明，难道压根就没打算让用户选择VALTH and VALTL ？

只看该作者 · 2014-5-29 09:30

楼主请参照第三章，这是一个综合性的章节。
3.7.1.4 ADC Analog Supply and Reference Connections
This device includes dedicated VDDA and VSSA pins.
This device contains separate VREFH and VREFL pins on 48-pin and higher devices.
These pins are internally connected to VDDA and VSSA respectively, on 32-pin devices.

3.7.1.5 ADC Reference Options
The ADC supports the following references:
• VREFH/VREFL - connected as the primary reference option
• VDDA - connected as the VALT reference option