IRS2330SPBF Datasheet, PDF (18/39 Pages) International Rectifier – 3-PHASE-BRIDGE DRIVER

IRS233(0,2)(D)(S&J)PbF
V_B1
V_CC
V_B2
V_B3
Figure 17: Internal bootstrap MOSFET connection
Figure 18: Bootstrap MOSFET state diagram
A bootstrap MOSFET is suitable for most of the PWM modulation schemes and can be used either in parallel with the external
bootstrap network (i.e., diode and resistor) or as a replacement of it. The use of the integrated bootstrap as a replacement of
the external bootstrap network may have some limitations. An example of this limitation may arise when this functionality is
used in non-complementary PWM schemes (typically 6-step modulations) and at very high PWM duty cycle. In these cases,
superior performances can be achieved by using an external bootstrap diode in parallel with the internal bootstrap network.
Bootstrap Power Supply Design
For information related to the design of the bootstrap power supply while using the integrated bootstrap functionality of the
IRS233(0,2)D family, please refer to Application Note 1123 (AN-1123) entitled “Bootstrap Network Analysis: Focusing on the
Integrated Bootstrap Functionality.” This application note is available at www.irf.com.
For information related to the design of a standard bootstrap power supply (i.e., using an external discrete diode) please refer
to Design Tip 04-4 (DT04-4) entitled “Using Monolithic High Voltage Gate Drivers.” This design tip is available at www.irf.com.
Separate Logic and Power Grounds
The IRS233(0,2)(D) has separate logic and power ground pin (VSS and VSO respectively) to eliminate some of the noise
problems that can occur in power conversion applications. Current sensing shunts are commonly used in many applications
for power inverter protection (i.e., over-current protection), and in the case of motor drive applications, for motor current
measurements. In these situations, it is often beneficial to separate the logic and power grounds.
Figure 19 shows a HVIC with separate VSS and VSO pins and how these two grounds are used in the system. The VSS is
used as the reference point for the logic and over-current circuitry; VX in the figure is the voltage between the ITRIP pin and
the VSS pin. Alternatively, the VSO pin is the reference point for the low-side gate drive circuitry. The output voltage used to
drive the low-side gate is VLO-VSO; the gate-emitter voltage (VGE) of the low-side switch is the output voltage of the driver
minus the drop across RG,LO.
www.irf.com
18