SBAU421B June   2023  – December 2023 TMCS1123

 

  1.   1
  2.   TMCS1123xEVM
  3.   Trademarks
  4. 1General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines
  5. 2Overview
    1. 2.1 Kit Contents
    2. 2.2 Related Documentation From Texas Instruments
  6. 3Hardware
    1. 3.1 Features
    2. 3.2 Circuitry
      1. 3.2.1 Bypass Capacitors
      2. 3.2.2 Output Filter
      3. 3.2.3 Overcurrent Set Point and Overcurrent Circuitry
      4. 3.2.4 Load Connectors
      5. 3.2.5 TMCS1123 Isolated Current-Sense Amplifier
  7. 4Operation
    1. 4.1 Measurements
    2. 4.2 Advanced Measurement Tips
  8. 5Schematics, PCB Layout, and Bill of Materials
    1. 5.1 Schematics
    2. 5.2 PCB Layout
    3. 5.3 Bill of Materials
  9. 6Revision History

3.2.3 Overcurrent Set Point and Overcurrent Circuitry

J1_x is a 1x3 header that allows the user to customize the input voltage reference of the overcurrent set point in a number of ways. Configuration options available include:

Option 1: Short J1_x pins 1 and 2 with the supplied shorting plug

This option provides the reference point with a voltage set through the potentiometer R5_x. R4_x is a 5.6-kΩ resistor that forms a voltage divider with the potentiometer that provides an output voltage. Use the following equations to calculate the overcurrent reference voltage presented to the VOC pin:

Equation 1. VOC=R4RPOT+R4×VS
Equation 2. for RPOT, max, VS=5.5V,  VOC=R4RPOT+R4×VS=5.60kΩ100kΩ+5.60kΩ×5.5V=0.291V≈0.3V
Equation 3. for RPOT, min, VS=5.5V,  VOC=5.60kΩ1kΩ+5.60kΩ×VS=0.85×VS

Note that the presence of the 5.6-kΩ resistor keeps the minimum output voltage available at approximately 0.3 V for the maximum device supply voltage of 5.5 V. This provides a quick method on board for analyzing nearly the entire voltage range of VOC. Check VOC with a digital multimeter (DMM) for the desired voltage, adjusting RPOT higher or lower until the desired voltage is achieved. See the TMCS1123 data sheet for information on how to calculate VOC for a given overcurrent set point.

Option 2: Short J1_x pins 2 and 3 with the supplied shorting plug

This option provides the reference point with the voltage produced by a resistor divider formed between R6_x and R7_x. This resistor divider is set to approximately 90% of VS by default (see Equation 4), but can be customized for evaluation between any resistor pair in 0805 package within data sheet specifications.

Equation 4. VOC=R7R6+R7×VS=88.7kΩ98.7kΩ×VS=0.9×VS

Option 3: Do not populate the shorting plug

By not populating the shorting plug, the reference input VOC remains floating from any hardwired PCB input. This node can then be driven directly by the "VOC" test point on the board to directly drive specific external voltage the user considers in their application.

The point set by any of the above methods are presented to an internal comparator, which is constantly monitored against the output voltage VOUT. In the event that VOUT > VOC, the active low nOC pin activates, pulling low to indicate that the system has reached the overcurrent point. Resistor R1_x acts as the pullup resistor for the active low nOC node.