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Negative Bias Image of onsemi's Negative Bias Chart Comparison

Silicon carbide MOSFET VGS thresholds tend to be lower than silicon junction MOSFETs. As the temperature goes up, the VGS threshold goes down. For example, onsemi’s NTH4L022N120M3S 1200 V, 22 mΩ silicon carbide MOSFET specifies a 2.72 V VGS threshold at +25ºC. However, at the maximum junction temperature of +175ºC, the VGS threshold can drop as low as 1.5 V. This low VGS threshold can be an issue during turn-off because the VGS can experience some ringing around 0 V, accidently turning on the silicon MOSFET during turn-off, which is a bad thing. To mitigate against this issue, the gate driver offers negative bias during turn-off. So instead of the VGS stopping at 0 V during turn-off, the gate driver turns off below 0 V; then any ringing will not trip the VGS threshold. The NCP51561 supports a negative bias voltage as low as minus 5.1 V.

PTM Published on: 2023-05-16