SLVSG43A December 2023 – November 2024 TPSI3100-Q1
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
The TPSI3100-Q1 has an internal nominal voltage reference (VREF) of 0.31V. This reference is shared by the fault and alarm comparator negative inputs.
The alarm event should be detected when the load current, ILOAD, reaches 4A nominal. The required shunt resistor can be computed as:
For this design, RSHUNT = 75mΩ, is used. From this, the nominal alarm current, IALM, detected can be computed:
The fault event should be detected when the load current, ILOAD, reaches 8A nominal. This corresponds to a voltage drop across the shunt resistor of VSENSE_FLT:
Since the fault comparator threshold of the TPSI3100-Q1 is also the nominal voltage reference (VREF) of 0.31V, a resistor divider is required to scale the VSENSE_FLT voltage to the comparator input threshold (VREF). The divider ratio (DIV) required can be calculated from:
For this design, the divider (DIV) was selected as 0.5. Therefore, R1 = R2. This leads to a nominal overcurrent of:
The power dissipated in the shunt resistor while remaining at the alarm condition can be computed as:
Similarly, the power dissipated in the shunt resistor at the overcurrent condition can be computed as:
A power rating for the shunt resistor should be chosen that is sufficient to handle these power conditions compared to those experienced during normal loading. If the system can take necessary action in a timely manner upon an alarm condition, a 2W power rated resistor is deemed sufficient. An overcurrent event causes the driver to be disabled quickly by the TPSI3100-Q1, and the overload current exists for short duration. A more conservative approach is to select a 5W power rated resistor.