Agilent 5991-4656EN Internal Gate Resistance Measurement Using the B1505A - Application Note c20140829 [8] free download

File name 5991-4656EN Internal Gate Resistance Measurement Using the Agilent B1505A - Application Note c201408

Keysight Technologies Internal Gate Resistance Measurement Using the B1505A Application Note Introduction Power MOSFET and IGBT internal gate resistance is an important device paramteter, since it can limit the maximum switching frequency or determine the driving loss in switching converters and inverters. For the lower totem pole transistor of the converter output, it is also important to minimize the internal gate resitance to prevent device self turn-on. Device self turn-on is caused by transient currents injected into the gate terminal of the lower totem pole transistor through capacitive coupling when the upper totem pole transistor turns on (refer to igure 1). Since this phenomena can cause device destruction, controlling internal gate resistance variations is as important as minimizing the absolute gate resistance value. Unfortunately, most data sheets only show typical values for the internal gate resitance. Since the internal gate resitance has a strong temperature dependence, measuring it for many devices under actual use conditions is necessary to understand its true value and temperature behavior. Internal gate resistance is typically measured at a speciic frequency using an LCR meter. The Keysight Technologies, Inc. B1505A power device analyzer/curve tracer has an LCR meter module option for power device capacitance measurement. This module therefore gives the B1505A the ability to also measure internal gate resistance. This application note explains how to measure internal gate resistance using the B1505A and also shows an actual example measurement. Driving Loss D G High Side MOS FET S Vin Controller IC D G Low Side MOS FET Vout S Self -Turn -On FIGURE 1. Driving loss and self-turn-on induced by internal gate resistance in a DC-DC converter 03 | Keysight | Internal Gate Resistance Measurement Using the B1505A - Application Note Measurement Fundamentals Figure 2 shows the simpliied cross section of a trench gate type power MOSFET. Cgd is the gate to drain capacitance, Cgs is the gate to source capacitance, and Cds is the drain to source capacitance. In addition to these capacitances, the gate to channel capacitance (Cgc) is also shown. The internal gate resistance, Rg(int), is in series with Cgd, Cgs and Cgc.