[Introduction]In the previous article, as a premise to introduce the effect of the driver source pin, we learned about the Voltage during switching operation in a conventional packaged MOSFET without a driver source pin (hereinafter referred to as “conventional MOSFET”). . In this article, together we will understand the operation of a MOSFET with a driver source pin and the effect of the driver source pin.
Key takeaways from this article
・Have driver source pins to eliminate the influence of VLSOURCE on VGS_INT.
・A driver source pin is provided to increase the turn-on speed.
In the previous article, as a premise for introducing the effect of the driver source pin, we looked at the voltage during switching operation in a conventional packaged MOSFET without a driver source pin (hereafter referred to as “conventional MOSFET”). In this article, together we will understand the operation of a MOSFET with a driver source pin and the effect of the driver source pin.
Differences with and without driver source pins and their effects
The lower left figure is a conventional MOSFET driver circuit, and the lower right figure is a MOSFET driver circuit with a driver source pin. The difference is the connection method of the return line of the drive circuit. In the past, the MOSFET was connected to the source (Source) pin, while the MOSFET with the driver source pin was connected to the driver source pin (Driver Source) pin. Its source is a separate Power Source pin. Also, each blue arrow represents the voltage in the switching operation.
As shown by the blue arrows, both voltages are the same during switching operation. Again, after the MOSFET is applied with VG and turned on, ID increases and LSOURCE produces VLSOURCE in the direction of (I) in the figure. Since the current IG flows into the gate pin, a voltage drop VRG_EXT(I) is generated due to RG_EXT.
As described above, the voltages generated by both are the same. However, in the case of conventional MOSFETs, VLSOURCE and VRG_EXT(I) are included in the drive circuit network during turn-on, so the on-chip required for MOSFET turn-on operation The voltage of VGS_INT will decrease, eventually resulting in lower turn-on speed. In the case of a driver source pin, the ID will flow to the power (Power Source) pin, not to the driver source (Driver Source) pin, this part is not included in the driver circuit network, so the VLSOURCE pair can be eliminated. Effects of VGS_INT.
If driver source pin is available, it can be removed
item (=VLSOURCE), it can be seen that this part of the voltage will not affect VGS_INT. This is the effect of the driver source pin, which increases the turn-on speed.
In the next article, we will look at the effect of the driver’s SOURCE pin by working with waveforms.