ZHCSFM4B september 2016 – december 2021 UCC21521
PRODUCTION DATA
- 1 特性
- 2 應(yīng)用
- 3 說明
- 4 Revision History
- 5 Pin Configuration and Functions
-
6 Specifications
- 6.1 Absolute Maximum Ratings
- 6.2 ESD Ratings
- 6.3 Recommended Operating Conditions
- 6.4 Thermal Information
- 6.5 Power Ratings
- 6.6 Insulation Specifications
- 6.7 Safety-Related Certifications
- 6.8 Safety-Limiting Values
- 6.9 Electrical Characteristics
- 6.10 Switching Characteristics
- 6.11 Insulation Characteristics Curves
- 6.12 Typical Characteristics
- 7 Parameter Measurement Information
- 8 Detailed Description
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Application
- 9.2.1 Design Requirements
- 9.2.2
Detailed Design Procedure
- 9.2.2.1 Designing INA/INB Input Filter
- 9.2.2.2 Select External Bootstrap Diode and its Series Resistor
- 9.2.2.3 Gate Driver Output Resistor
- 9.2.2.4 Gate to Source Resistor Selection
- 9.2.2.5 Estimate Gate Driver Power Loss
- 9.2.2.6 Estimating Junction Temperature
- 9.2.2.7 Selecting VCCI, VDDA/B Capacitor
- 9.2.2.8 Dead Time Setting Guidelines
- 9.2.2.9 Application Circuits with Output Stage Negative Bias
- 9.2.3 Application Curves
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
- DW|16
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- DW|16
訂購信息
9.2.2.2 Select External Bootstrap Diode and its Series Resistor
VDD charges the bootstrap capacitor through an external bootstrap diode every cycle when the low-side transistor turns on. Charging the capacitor involves high-peak currents, and therefore transient power dissipation in the bootstrap diode may be significant. Conduction loss also depends on the diode’s forward voltage drop. Both the diode conduction losses and reverse recovery losses contribute to the total losses in the gate driver circuit.
When selecting external bootstrap diodes, choose high-voltage, fast recovery diodes or SiC Schottky diodes with a low forward voltage drop and low junction capacitance to minimize the loss introduced by reverse recovery and related grounding noise bouncing. In the example, the DC-link voltage is 800 VDC. The voltage rating of the bootstrap diode should be higher than the DC-link voltage with a good margin. Therefore, a 1200-V SiC diode, C4D02120E, is chosen in this example.
When designing a bootstrap supply, it is recommended to use bootstrap resistor, RBOOT. A bootstrap resistor is also used to reduce the inrush current in DBOOT and limit the ramp up slew rate of voltage of VDDA-VSSA during each switching cycle. A bootstrap resistor also helps reduce a bootstrap voltage overshoot due to large a switch node undershoot.
Failure to limit the voltage to VDDx-VSSx to less than the Absolute Maximum Ratings of the FET and UCC21521 may result in permanent damage to the device in certain cases.
The recommended value for RBOOT is between 1 Ω and 20 Ω depending on the diode used. In the example, a current limiting resistor of 2.2 Ω is selected to limit the inrush current of bootstrap diode. The estimated worst-case peak current through DBoot is as follows:
where
- VBDF is the estimated bootstrap diode forward voltage drop at 8 A.