IRFB18N50K_RC, SiHFB18N50K_RC Vishay Siliconix R-C Thermal Model Parameters DESCRIPTION The parametric values in the R-C thermal model have been derived using curve-fitting techniques. R-C values for the electrical circuit in the Foster/tank and Cauer/filter configurations are included. When implemented in P-SPICE, these values have matching characteristic curves to the single-pulse transient thermal impedance curves for the MOSFET. These RC values can be used in the P-SPICE simulation to evaluate the thermal behavior of the MOSFET junction temperature under a defined power profile. These techniques are described in application note AN609, “Thermal Simulation of Power MOSFETs on the P-SPICE Platform”. R-C THERMAL MODEL FOR TANK CONFIGURATION T (Junction) RT1 RT2 RT3 RT4 CT1 CT2 CT3 CT4 T (Ambient) R-C VALUES FOR TANK CONFIGURATION THERMAL RESISTANCE (°C/W) Junction to Ambient Case Foot RT1 N/A 54.0854 m N/A RT2 N/A 123.7768 m N/A RT3 N/A 248.6800 m N/A RT4 N/A 133.4578 m N/A THERMAL CAPACITANCE (Joules/°C) Junction to Ambient Case Foot CT1 N/A 4.1414 m N/A CT2 N/A 150.3016 m N/A CT3 N/A 150.2554 m N/A CT4 N/A 24.7654 m N/A Note N/A indicates not applicable This document is intended as a SPICE modeling guideline and does not constitute a commercial product datasheet. Designers should refer to the appropriate datasheet of the same number for guaranteed specification limits. Document Number: 90422 Revision: 16-Apr-10 www.vishay.com 1 IRFB18N50K_RC, SiHFB18N50K_RC Vishay Siliconix R-C THERMAL MODEL FOR FILTER CONFIGURATION T (Junction) RF2 RF1 CF1 CF2 RF3 RF4 T (Ambient) CF4 CF3 GND R-C VALUES FOR FILTER CONFIGURATION THERMAL RESISTANCE (°C/W) Junction to Ambient Case RF1 N/A 57.9136 m Foot N/A RF2 N/A 187.5157 m N/A RF3 N/A 134.3644 m N/A RF4 N/A 180.2063 m N/A THERMAL CAPACITANCE (Joules/°C) Junction to Ambient Case CF1 N/A 2.2453 m Foot N/A CF2 N/A 14.4841 m N/A CF3 N/A 44.1958 m N/A CF4 N/A 99.7504 m N/A Note N/A indicates not applicable www.vishay.com 2 Document Number: 90422 Revision: 16-Apr-10 IRFB18N50K_RC, SiHFB18N50K_RC Vishay Siliconix Document Number: 90422 Revision: 16-Apr-10 www.vishay.com 3