JAJSDD3B June 2017 – January 2019 TPS53681
PRODUCTION DATA.
This section describes designing the thermal compensation network. The NTC thermistor is used to compensate thermal variations in the resistance of the inductor winding. The winding is usually copper. And as such has a resistance coefficient of 3900 PPM/°C. Alternatively, the NTC thermistor characteristic is very non-linear and requires two or three resistors to linearize them over the range of interest. Figure 73 shows a typical DCR circuit.
Equation 8 calculates the voltage across the CSENSE capacitor when it exactly equals the voltage across RDCR.
where
Ensure that CSENSE is a capacitor type which is stable over temperature, use X7R or better dielectric (C0G preferred). Because calculating these values by hand can be time-consuming, TI offers a spreadsheet using the Excel Solver function available to provide calculation assistance. Contact your local TI representative to get a copy of the spreadsheet.
This example uses a simple design process to enable input shunt sensing, so no DCR network is needed. Insert a 0.5-mΩ shunt resistor in series between the input inductor and the input bulk capacitors.