ZHCSTB0E February 2010 – November 2023 UCC27321-Q1 , UCC27322-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 应用
- 3 说明
- 4 说明（续）
- 5 Related Products
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Revision History
- 14Mechanical, Packaging, and Orderable Information
8.3.3 Source and Sink Capabilities During Miller Plateau
Large power MOSFETs present a large load to the control circuitry. Proper drive is required for efficient, reliable operation. The UCC2732x-Q1 drivers have been optimized to provide maximum drive to a power MOSFET during the Miller plateau region of the switching transition. This interval occurs while the drain voltage is swinging between the voltage levels dictated by the power topology, requiring the charging or discharging of the drain-gate capacitance with current supplied or removed by the driver.
Two circuits are used to test the current capabilities of the UCC2732x-Q1 driver. In each case, external circuitry is added to clamp the output near 5 V while the device is sinking or sourcing current. An input pulse of 250 ns is applied at a frequency of 1 kHz in the proper polarity for the respective test. In each test, there is a transient period when the current peaked up and then settled down to a steady-state value. The noted current measurements are made at a time of 200 ns after the input pulse is applied, after the initial transient.
The circuit in Figure 8-1 is used to verify the current-sink capability when the output of the driver is clamped at approximately 5 V, a typical value of gate-source voltage during the Miller plateau region. The UCC2732x-Q1 is found to sink 9 A at VDD = 15 V.
Figure 8-1 Sink Current Test CircuitThe circuit in Figure 8-2 is used to test the current-source capability with the output clamped to approximately 5 V with a string of Zener diodes. The UCC2732x-Q1 is found to source 9 A at VDD = 15 V.
Figure 8-2 Source Current Test CircuitThe current-sink capability is slightly stronger than the current source capability at lower VDD. This is due to the differences in the structure of the bipolar-MOSFET power output section, where the current source is a P-channel MOSFET and the current sink has an N-channel MOSFET.
In a large majority of applications, it is advantageous that the turnoff capability of a driver is stronger than the turnon capability. This helps to ensure that the MOSFET is held off during common power-supply transients that may turn the device back on.