SPM6M080-010D_10 Datasheet, PDF (13/16 Pages) Sensitron – Three-Phase MOSFET BRIDGE, With Gate Driver and Optical Isolation

SENSITRON
SEMICONDUCTOR
TECHNICAL DATA
Datasheet 4118, Rev. D.2
SPM6M080-010D
e- Active Bias For Desaturation Detection Circuit:
The desaturation detection is done by diode D2 for the high side MOSFET Q1H, and by
diode D3 for the low side MOSFET Q1L. The internal detection circuit, input DSH for the
high-side and input DSL for the low-side, is biased by the local supply voltage VCC for the
low side and VBS for the high side. When the MOSFET is on the corresponding detection
diode is on. The current flowing through the diode is determined by the internal pull
resistor, R1 for the high side and R2 for the low side. To minimize the current drain from
VCC and VBS, R1 and R2 are set to be 100KΩ. Lower value of R1 will overload the
bootstrap circuit and reduce the bootstrap capacitor holding time.
To increase the circuit noise immunity, an active bias circuit is used to lower R1 and R2
when the corresponding MOSFET is off by monitoring the input voltage at both DSH, DSL
inputs. If the inputs at DSH drops below 7V the active bias is disabled. The active bias
circuits result in reducing R1 or R2 to about 110 Ω when the corresponding input is above
8V, as shown in Fig. 8. This active circuit results in higher noise immunity.
R1
R1
100KΩ
R1
110Ω
7V
8V
VDSH
Figure 8. Active Bias for DSH and DSL Internal Inputs
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