SWRU629 September   2024

 

  1.   1
  2.   Description
  3.   Features
  4.   4
  5. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  6. 2Hardware
    1. 2.1 Wired Connections, Jumper Settings, Buttons, and LEDs
      1. 2.1.1  SWD Interface
      2. 2.1.2  I2C Connections
        1. 2.1.2.1 Default I2C Addresses
      3. 2.1.3  UART Signals
      4. 2.1.4  SD Card Interface
      5. 2.1.5  External Memory Interface
      6. 2.1.6  ADC Interface
      7. 2.1.7  Reset Pull-up Jumper
      8. 2.1.8  Push Buttons
      9. 2.1.9  LED Indicators
      10. 2.1.10 LaunchPad Header Pin Assignment
    2. 2.2 Power
      1. 2.2.1 VIO Selection
      2. 2.2.2 Measure the CC35xxE Current Draw
        1. 2.2.2.1 Low Current Measurement (LPDS)
        2. 2.2.2.2 Active Current Measurement
    3. 2.3 Clocking
    4. 2.4 Conducted RF Testing
    5. 2.5 Evaluation Setup
      1. 2.5.1 Wi-Fi Toolbox LP-EM-CC35X1 Hardware Setup
  7. 3Hardware Design Files
    1. 3.1 Schematics
    2. 3.2 PCB Layouts
    3. 3.3 Bill of Materials (BOM)
  8. 4Additional Information
    1. 4.1 Trademarks

2.1.6 ADC Interface

The CC35xxE features a 12-bit ADC with 8 channels. The LP-EM-CC35X1 enables use of 4 ADC channels with onboard buffers for impedance controlling. The two OPA2211 dual channel operational amplifiers (U7, U10), which are configured as impedance buffers for four ADC channels can be seen in Figure 2-12.

LP-EM-CC35X1 ADC Buffers Figure 2-12 ADC Buffers

The four ADC channels which are available on the LP-EM-CC35X1 are ADC2, ADC3, ADC4, and ADC5. A jumper is also provided to disconnect the power to U7 and U10 for current measurements of the CC35xx.

If users want to use the corresponding GPIOs which are used as the ADC channels without the buffers, then there is the possibility to route around the buffers by removing and placing certain 0 ohm resistors.

The GPIO configuration of the ADC channels and which resistors need to be changed for buffer reroute can be seen in Table 2-5.

Table 2-5 ADC GPIO Configuration
ADC Channel GPIO # (CC35xx) LaunchPad Header Pin # Needed Configuration For Unbuffered GPIO Use
ADC2 GPIO6 23 remove: R44, R52

place: R71

ADC3 GPIO5 24 remove: R73, R75

place: R79

ADC4 GPIO4 25 remove: R41, R50

place: R70

ADC5 GPIO3 26 remove: R72, R74

place: R78

The locations of the resistors mentioned in Table 2-5 can be seen in Figure 2-13.

As an example, if users want to use GPIO4 unbuffered, which is connected to LaunchPad header pin 26 on the LP-EM-CC35X1, then the following resistors need to be changed:

  • Remove R41 and R50
  • Place 0 ohm resistor (0201) R70
LP-EM-CC35X1 ADC Buffer Reroute Configuration Figure 2-13 ADC Buffer Reroute Configuration

The area of the LP-EM-CC35X1 schematic which encompasses the ADC buffers is shown in Figure 2-14.

LP-EM-CC35X1 ADC Buffers Schematic Figure 2-14 ADC Buffers Schematic