SDAA080 September   2025 TPS2HCS08-Q1 , TPS2HCS10-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2High Side Switch Current Sense and Open Load Detection
    1. 2.1 Current Sense in High-side Switches
    2. 2.2 Open-Load Detection in High-side Switches
  6. 3Smart eFuse Current Sense and Open Load Detection
    1. 3.1 Open Load Detection in eFuses
    2. 3.2 Open-Load Current Sense Scaling
    3. 3.3 ADC Input Scaling
    4. 3.4 OL_ON and ADC Input Scaling Programming Procedure
  7. 4Normal vs. Open-Load Scaling Test Results
  8. 5Design Considerations
  9. 6Summary
  10. 7References

4 Normal vs. Open-Load Scaling Test Results

Below is an example system where TPS2HCS08-Q1 supplies power to a variable load, such as a zonal controller that has multiple output rails and low power modes. The nominal full-power current sense accuracy is recorded, then the default current sense accuracy is compared to the current sense accuracies using KSNS2 and KSNS2 with an 8x ADC scaling, respectively, are compared.

This test uses the data sheet-recommended RSNS value of 698Ω. The equation to calculate the output current from the resulting ADC code is as follows:

Equation 1. IOUT=[KSNS*VADCREFHI/[1023*RSNS*ISNSSCALE]]*ADC_RESULT (Equation 1)

Where:

KSNS = 5000 for KSNS1; 1400 for KSNS2

ISNS_SCALE = 1 for no ADC Scaling; 8 for ADC Scaling

VADCREFHI = 2.81V typ.

RSNS = 698Ω

Table 4-1 through Table 4-3 detail the current sense accuracy at 10A, 100mA, 10mA, and 0mA with each KSNS and ADC scaling factor applied. Table 4-1 shows the results in terms of ADC codes, Table 4-2 in terms of calculated output current, and Table 4-3 in terms of accuracy.

Table 4-1 Current Sense ADC Codes
KSNS1KSNS2KSNS2 and ADC Scaling
10A506N/AN/A
100mA4118E
10mA019
0mA006
Table 4-2 Current Sense Output
KSNS1KSNS2KSNS2 and ADC Scaling
10A9.956AN/AN/A
100mA78.8mA93.7mA97.8mA
10mA0mA0.689mA6.2mA
0mA0mA0mA4.1mA
Table 4-3 Current Sense Accuracy
KSNS1KSNS2KSNS2 and ADC Scaling
10A0.44%N/AN/A
100mA21.2%6.3%2.2%
10mAN/A93.11%38%
0mA0%0%N/A

Overall, there are two main trends that require the use of OL_ON mode and ADC scaling. The first is that the accuracy is significantly improved at lower currents using these two features. The second is that, at 100mA and below, the 10-bit ADC's resolution using KSNS1 is 19.7mA. However, using KSNS2 with 8x ADC scaling, the ADC's resolution becomes 0.688mA, allowing for a much smaller differentiation between low currents.