SLVUDD8 September   2025 LM50 , LM50-Q1

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  8. 2Hardware
    1. 2.1 Overview
    2. 2.2 Perforations
    3. 2.3 Status LEDs and Subregulator
    4. 2.4 Programming Header
    5. 2.5 Pushbutton Switch
    6. 2.6 RC Filter
  9. 3Software
    1. 3.1 Software Download
      1. 3.1.1 Online Software
      2. 3.1.2 Offline Software
    2. 3.2 Home Tab
    3. 3.3 Data Capture Tab
    4. 3.4 Collateral Tab
  10. 4Hardware Design Files
    1. 4.1 LM50HVEVM Schematic
    2. 4.2 PCB Layout
    3. 4.3 Bill of Materials (BOM)
  11. 5Additional Information
    1. 5.1 Trademarks
  12. 6Related Documentation

2.6 RC Filter

On the sensor breakout board, R13 and C20 can be used for an optional RC circuit to filter the voltage output of the LM50HV. R13 is already installed on the board, but is a 0Ω jumper so acts as a short. C20 is not installed by default. The user can desolder R13, solder on a different resistor in the place of R13, and solder on a capacitor for C20 to create an RC filter.

The user must be aware to not use a capacitor value greater than 900nF for C20. The LM50HV has a maximum capacitive load of 1uF, however C19 on the controller portion of the EVM is a 100nF cap that is loaded onto the output voltage line. C19 prevents the voltage from dropping on the microcontroller ADC input, so C19 must not be removed. The ADC pin of the MSP430F5528 has 15pF of capacitive loading as well, although this is considered negligent when working on the scale of hundreds of nF.

To maintain output stability, phase margin (PM) must not be allowed to drop below 65°. When choosing a resistor and capacitor for an RC filter, refer to the data sheet to find resistor and capacitor values to keep the PM above 65° (see Section 6). C19, the 100nF capacitor placed near the ADC on the MCU side of the PCB, does count as part of the total capacitance for the PM calculation. For example if the user wants a filter with 200nF and 950Ω, the user must install a 100nF capacitor for C20.