Using the MAX11311 Internal and External Temperature Sensor


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Keywords: Programmable, ADCs, DACs, Digital I/Os, Analog Switches
APPLICATION NOTE 6311
USING THE MAX11311 INTERNAL AND EXTERNAL TEMPERATURE SENSOR TO ACTIVATE MOTORS AND FANS
Abstract: The MAX11311 is a 12-port PIXI™ device that is a programmable mixed I/O with 12-bit ADC, 12bit DAC, analog switches, and GPIO. This application note describes how to design the MAX11311 with control loops. The Atmel ATMEGA328 can communicate with the MAX11311 through the SPI interface. Included in the application note are complete schematics and firmware.
Introduction
The MAX11311 integrates a PIXI™ 12-bit, multichannel, analog-to-digital converter (ADC) and a 12-bit, multichannel, buffered digital-to-analog converter (DAC) into a single integrated circuit (IC). In this application note, we use a MAX11311 LiveLab Demo board to demonstrate how the internal and external temperatures sensors are used to activate the DC motor, LED, alarm, and three fans (two for external temperature sensors, and the other for internal temperature sensor with a Peltier cooling device beneath the device).
Figure 1 shows the MAX11311 LiveLab Demo board, and Figure 2 shows the MAX11311 block diagram.
We focus on four demo scenarios. With the provided schematics and firmware, designers can customize to their requirements using their own hardware.

Figure 1. MAX11311 LiveLab Demo board. Figure 2. MAX11311 block diagram.

Schematics and Source/Demo Files Download the following items to get started:
MAX11311 LiveLab Demo Schematics Microcontroller Source Files MAX11311 Demo Files
Development Process
With the 12 ports available on the PIXI, the flowchart in Figure 3 provides an idea on how to start designing with the PIXI.
Figure 3. MAX11131 development process flowchart.
What Should the Board Demonstrate?
Here we consider four demo scenarios. Note that Px is one of the 12 ports on PIXI. Demo 1: INT temperature regulated by Peltier junction with BLDC fan mounted underneath PIXI.
P0: DAC BLDC fan cooling INT temperature, output level 4V, voltage range 0 to 10V P1: DAC Peltier TEC cooling INT temperature, internal reference, output level 1.5V, voltage range 0 to 10V P2: GPO LED alarm INT temperature, output level 3.3V P8: GPO buzzer INT temperature, output level 10V Demo 2: EXT1 temperature regulated by BLDC fan. P3: DAC BLDC fan cooling EXT1 temperature, internal reference, output level 4V, voltage range 0V to 10V

P4: GPO LED alarm EXT1 temperature, output level 3.3V P5: ADC trim pot set point EXT1 temperature, internal reference, voltage range 0V to 10V P8: GPO buzzer EXT1 temperature, output level 10V Demo 3: EXT2 temperature regulated by BLDC fan.
P6: DAC BLDC fan cooling EXT2 temperature, internal reference, output level 4V, voltage range 0V to 10V P7: GPO LED alarm EXT2 temperature, output level 3.3V P9: GPO buzzer EXT2 temperature, output level 10V Demo 4: Periodic timer run 3VDC motor.
P9: DAC 3VDC motor emitter follower, internal reference, output level 0V, voltage range 0 to 10V P10: ADC trim pot speed 3VDC motor, # of samples 1, internal reference, voltage range 0 to 10V P11: ADC trim pot reserved duty cycle 3VDC motor, # of samples 1, internal reference, voltage range 0 to 10V By listing the ideas, we can map the discrete components into the PIXI equivalent, determine the pinout for the PIXI, and set parameters for the components.
Transferring Our Ideas to the Configuration Software The MAX11300 configuration software is a tool to simplify a design. It sets up the registers within the PIXI accordingly. Once the register (.csv) and programming (.h) files are created, the software developer has a foundation to start programming the device.
Within the configuration software, the following component fields are allowed in the design (see Figure 4).
Single Ended ADC Differential ADC DAC DAC with ADC Monitoring GPI GPO Level Translator B-Directional Level Xltr GPI Controlled Analog Switch Software Controlled Analog Switch
Each component is drag-and-dropped to the panel. Connections are made by left-clicking the mouse and dragging from port to input/output of the component, and vice versa. Figure 4 shows the PIXI demo board design. Within each component, parameters can be accessed using the right-click of the mouse and selecting Properties or by selecting the Properties tab on the right edge of the GUI. See Figure 5 for parameters of DAC with ADC Monitoring. Repeat each port on the PIXI until the desired connections and parameters are set.

Figure 4. MAX11131 configuration software design.
Figure 5. Properties for DAC with ADC Monitoring parameters window. Within the General Parameter Configuration menu option, the user can adjust voltages, DAC, ADC, interrupt mask, and general control. In this design, Figure 6 shows the configuration. Only applicable voltages are allowed. Refer to the IC data sheet for voltage ranges.

Figure 6. General Parameter Configuration menu window.
Within the Temperature Sensor Configuration menu item, the temperature interrupt mask and threshold can be set. In this design, Figure 7 shows the configuration. Only applicable temperatures are allowed. Refer to the IC data sheet for temperature ranges.

Figure 7. Temperature Sensor Configuration menu window. Within the User Notes menu item, users can write a description for each PIXI port.

Figure 8. User Notes menu window.
Once the design and parameters are set properly, it is time to save the design. Use the File ® Save As menu item and save as an .mpix file. See Figure 9.

Figure 9. Saving the .mpix file (File → Save As).
Register files for the design can be saved as a .csv file using File ® Generate Register menu item. See Figure 10.

Figure 10. Saving register files as .csv (File → Generate Register).
C header files can be saved using the File → Generate C Header File menu item. See Figure 11. This file follows Figure 14 found in the MAX11311 IC data sheet (PIXI port configuration flow chart).

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Using the MAX11311 Internal and External Temperature Sensor