JAJSJV7C december 2020 – may 2023 TPS272C45
PRODUCTION DATA
Table 10-3 shows the requirements for the load current sense in this application. The KSNS value is specified for the device and can be found in the Specifications section.
PARAMETER | EXAMPLE VALUE |
---|---|
Current sense ratio (KSNS) | 1200 |
Largest diagnosable load current | 2.4 A |
Smallest diagnosable load current | 50 mA |
Full-scale ADC voltage | 5 V |
ADC resolution | 10 bit |
The load current measurement up to 2.4 A ensures that even in the event of a overcurrent but below the set current limit, the MCU can register and react by turning off the FET while the low level of 50 mA allows for accurate measurement of low load currents and enable the distinction open load faults from nominal load currents.
The RSNS resistor value can be selected such that the largest diagnosable load current puts the SNS pin voltage (VSNS) less than the ADC full-scale. With this design, any ADC value that shows full scale (FS) can be considered a fault. Additionally, the RSNS resistor value must ensure that the smallest diagnosable load current does not cause VSNS to fall below at a least a few LSB of the ADC. With the given example values, a 2.4-kΩ sense resistor satisfies both requirements shown in Table 10-4.
LOAD (A) | SENSE RATIO | ISNS (mA) | RSNS (Ω) | VSNS (V) | % of 5-V ADC |
---|---|---|---|---|---|
2.4 | 1200 | 2.0 | 2400 | 4.8 | 96% |
0.024 | 1200 | 0.02 | 2400 | 0.048 | 0.96% (9 LSB) |